Tag Archive | air pore space

Rocks For Drainage In Pots: Do They Really Help?

Should We Add Rocks For Drainage?

Rocks for drainage?

This issue of adding rocks or gravel to a pot for better drainage has been debated for generations by amateur as well as professional gardeners. Gardening programs from decades ago recommended adding a few inches of gravel or broken clay pottery to the bottom of a pot before filling with potting soil.

That method has been put to the test and soundly debunked. It doesn’t work. In fact, it can retain even more water close to the plant’s roots!

Many gardeners are eager to start filling their patio pots with flowers and herbs. Or perhaps vegetable gardening in containers is on the agenda. For some, it has been a long, cold winter, and this activity signals the beginning of a new growing season. But, before buying that big bag of gravel for your pots, look over this information and see if you might consider doing things differently.

Ingredients In Potting Soil

Potting soils are composed of a few or several ingredients in various proportions. Certain components absorb and retain moisture around plant roots while others help the soil drain faster. Some materials do both, depending on how finely they were milled.

This article describes how components behave in potting soil, and how gravity and other forces exert their influence on drainage and water retention. I’ll also suggest why it’s better to exclude rocks for drainage in pots.

Here are some of the ingredients commonly found in potting soils, in addition to water and air:

Organic materials, which help retain water:

peat moss, which holds water between its fibers
coconut coir, chopped into fine particles (for water retention) or left in longer fibers (more aeration)
pine fines, which decompose quite slowly; most often used to facilitate drainage in potting soil and in gardens, but finely milled pine fines hold water
compost, a nutrient-rich material
aged manure, composted to kill pathogens

: Coconut before processing into coir.

: Compost.

: Pine fines.

Potting soils might contain other types of materials, including ground shellfish, kelp, alfalfa meal, rice hulls, sawdust, charcoal, blood meal, bone meal, earthworm castings, and bat guano. Some manufacturers add various species of beneficial microbes.

Although not organic matter, fine clay holds water between its particles. Most potting soils contain no soil and are, in fact, soilless. A few include loam in the mix.

“Sinking Soil Syndrome”

You might have noticed the surface of the soil dropping lower in an old potted houseplant. The soil probably isn’t eroding through the drainage hole in the bottom of the pot, so where is it going?

Organic matter in the soil decomposes. As it oxidizes, and gets “used up”, its volume reduces considerably. Over time, you’ve seen the soil level dropping an inch or two, maybe more. On the contrary, sand and other gritty materials hold their volume.

The remedy for this sinking soil syndrome is to take the plant out of the pot and to refresh the potting soil. Pack new soil firmly around the roots to prevent settling. Don’t cover the stems or the crown of the plant with soil—just the roots. After that, the plant should be fine for another few years.

Beaucarnea recurvata, ponytail palm.

Several years ago, I was about to transplant a severely potbound ponytail palm (like the one in photo, above) into a larger clay pot. That plant came with me from Maryland and had been in its 4½” pot for close to a decade. It’s a very durable plant!

After removing it from the plastic pot, all that remained under the trunk were the roots, perlite, and sand clinging to the roots. It looked like a wire sculpture—a tracery of root and grit and mostly air taking the shape of the pot, but no peat moss or other organic matter. It transplanted successfully, and now sits on the back deck in mild weather.

Reusing Potting Soil

Many customers have asked about potting new plants into potting soil that has been used before. If there is still a substantial organic component and the soil has good tilth, then it can be used again. But, first, fluff up the soil and supplement with compost, potting soil, or some of the other amendments.

Rather than risk infecting new plants, toss old soil that held diseased plants into an active compost pile or the woods. Plants known to be vulnerable to soil-borne diseases (basil, in particular) are best planted in fresh potting soil and a thoroughly cleaned pot. When I lost an heirloom tomato to a fungal disease a few years ago, I removed the plant and the top layer of soil. After adding fresh potting soil, I planted a disease-resistant tomato, which grew fine for the rest of the season.

Inorganic materials, which increase drainage:

perlite, a heat-expanded mineral, those little white particles
expanded rock, such as PermaTill, another heat-expanded mineral
horticultural grit
vermiculite, not used as often today because it can compress and lose its drainage capacity
coarse or sharp sand and gravel—angular-edged particles, as opposed to rounded particles, can help drainage if they aren’t too small

: Sharp sand.

: Orchid mix on the left, organic matter on the right.

Chunky expanded clay and rock, often found in succulent and orchid mixes (photo, above), provide fast drainage and excellent air circulation around the roots.

Qualities such as tilth, water retention, nutrient capacity, and aeration of the soil are determined by the particular combination of materials and the sizes of their particles. Larger particles tend to facilitate aeration and drainage, while tiny particles (especially clay soil) retain water in the tight spaces between them.

Air Pore Space and Gravity

Air pore spaces occupy the voids between soil particles when they’re not taken up by water. Water flows through the soil profile, following the force of gravity. As water drains away and as the roots absorb it, air infiltrates the medium, providing oxygen for the roots. Plant cells use oxygen in respiration, as they oxidize the products of photosynthesis (glucose) and expel carbon dioxide as a waste product.

“Wait, what?” Yes, plants give off carbon dioxide during respiration. The net effect in each 24-hour period, however, is more oxygen given off during photosynthesis than is consumed during respiration. This process creates energy needed by plants to make new cells and to carry out hundreds of cellular activities.

Wilted marjoram ‘Compactum’.

Plants continually grow tiny new root hairs right behind the expanding root tips. Oxygen is critical to respiration and, therefore, to new root growth. These short-lived root hairs do most or all of the water absorption and interact with beneficial fungal mycorrhizae in almost all species of plants.

Brassicas (broccoli, cabbage, kale, etc.) do not participate in this mycorrhizal/root relationship. A few other groups of plants (Ericaceous plants, orchids, sedges, spinach, and beets) have rare forms of mycorrhizae colonizing in or around their roots.

Saturated soil kills root hairs. If this condition persists, the roots themselves will die and not regrow. If roots and root hairs can’t supply water to the leaves, the foliage wilts. The plant’s wilted appearance looks the same as when the plant has been deprived of water. Either overwatering or underwatering prevents water from reaching the leaves once the roots have been suffocated or dehydrated.

Feel the Soil

An extended period of wilt and wet soil is a common reason for plant failure. Even if the soil surface feels dry, there’s usually adequate moisture deeper into the pot. That’s why we recommend feeling the soil an inch or two into the pot.

Soil texture, pot size, sunlight, temperature, the plant’s leaf surface area, and, of course, frequency of watering influence how quickly potting soil drains and dries.

Capillarity

The force that works in opposition to gravity is capillary action. Water drains between soil particles, thanks to gravity, allowing most of the excess to pass through the holes in the bottom of the pot. But water also can move upward or sideways in the pot due to capillary action.

Capillarity is part cohesion and part adhesion, two kinds of forces between molecules. Cohesion is the attraction of water molecules to each other. Adhesion is the attraction of water molecules to other substances, such as particles of potting soil or the xylem tubes in a plant’s vascular system. In capillary attraction, adhesion is a stronger force than cohesion, so water molecules will stick to and be drawn between particles or along the inside surfaces of xylem.

As water molecules on the soil surface evaporate, they’re replaced by water molecules below them because of capillarity.

So, there’s a constant battle waged between gravity and capillarity. Water moves toward the bottom of the pot, but is limited by capillarity, which pulls it upward. What does this have to do with using rocks for drainage in a pot? I’ll explain in a moment. But first…

A Simple Experiment

Here’s an experiment that illustrates these points. Because organic soils often don’t contain wetting agents, which help the soil absorb water more readily, look for fresh potting soil that is not certified organic. Fill a short pot and a tall pot with dry or barely damp potting soil, using no rocks. Pack it in evenly and moderately firmly.

Now, place each pot in a shallow bowl of warm water. Why warm? Because soil absorbs warm water faster than it absorbs cold water. If the water disappears into the soil, add more to the bowl.

Wait an hour or so. In the short pot, you’ll see moisture on the surface. It might take longer for the larger pot to absorb water. If water remains in the bowl without moving all the way to the surface in the tall pot, the force of gravity has exceeded the ability for capillarity to pull the water farther upward. Moisture can wick into the soil by capillarity only up to a certain point.

If the tall pot is moist on the surface, the soil might have more water-retentive components than drainage materials. Tiny clay particles also can absorb water and hold it tightly. Try using a taller pot. Watering a plant in a very tall pot from the saucer usually necessitates additional water applied to the surface when capillarity fails to moisten the soil all the way to the top.

Movement of moisture within the medium depends on the dimensions of the container and the texture of the soil. Soil with larger air pore spaces will have more difficulty absorbing water all the way to the surface of the pot.

Water Tables and Rocks For Drainage

The Perched Water Table

It seems logical that soil would drain better when rocks are added to the bottom of the pot. But, to the contrary, rocks can slow down water trying to exit through the drainage holes. And it all has to do with those air pore spaces.

Gravel by itself has large air pore spaces between the pieces. So, water will pass through them after some of it adheres to the surface of the gravel. You’d think that potting soil on top of the gravel should drain freely. While water does drain freely close to the surface of the soil, percolation slows as the water approaches the layer of gravel.

Gravity removes much of the excess water. At some point, though, water does not move readily from soil (with small air pore spaces) to the rocks (with large air pore spaces). The water sits at the bottom of the soil volume and hesitates moving into the rocks. This creates a “perched water table”, a layer of soggy soil above the rocks.

How Soil Drains In the Garden

Soil in the garden behaves differently. Gravity continuously pulls water down through the soil profile. Water percolates toward an aquifer, or it hits a layer of extremely compacted clay soil, called hardpan. When it hits the hardpan, water either pools there or slowly drains down the slope of the hardpan a foot or a few feet underground.

Much of the water, of course, will be used by plants, drain downslope, or evaporate to the atmosphere. The rest of the surface runoff drains toward roads, storm basins, or ditches, ultimately ending up in streams and other bodies of water.

Remember the Wet Sponge Experiment?

Soak a rectangular sponge in water until it’s saturated. Held horizontally, it contains the maximum amount of water the sponge can hold. Now, turn it upright, with the bottom edge horizontal. More water drips from the bottom of the sponge, right? The longer vertical axis of the sponge allows more water to drain as water passes from one part of the sponge to a lower part.

The air pore space is consistent throughout the sponge, so water is pulled through. You’ll notice that the bottom of the sponge is the wettest part. But eventually it will stop dripping. Now, hold the sponge on an angle, and the sponge will drip a bit more water from the corner to the air below.

At one point, the sponge will feel wet, but it won’t drip. As long as there’s material for water to drain to, you might be able to coax more water from the sponge. For example, if you hold a paper towel—even a wet one—to the bottom of the sponge, the paper towel will draw more water from the sponge because of gravity.

Air under the sponge—or gravel in the bottom of a pot—has large air pore spaces. Consequently, water won’t move from the sponge—or from the potting soil—into the gravel. Gravity can do only so much; after that, some kind of material with similar air pore space is needed to draw water through the soil. Then, when no more water can drain by gravity, capillarity will hold water in the sponge or in the perched water table.

The Water Table

We see that the flow of water is impeded at the interface between the soil and the rocks. A pot filled with only potting soil (no rocks for drainage) also holds water above the bottom of the pot. After excess water drains through the holes, that lowest region of soil will feel wet compared to the upper layer.

The difference between a pot with rocks for drainage and one without rocks is the soil volume occupied by the roots. A plant grows a more extensive root system in a pot without rocks, allowing larger and more vigorous top growth. A plant with a compromised root system, from soil that drains poorly, ordinarily will not grow as vigorously. In fact, it might get off to a difficult start due to the presence of constant moisture in the perched water table.

Conformation of nursery pots I’ve bought over the years consider these aspects of soil drainage. Here’s one where the bottom of the pot is molded higher in the center. This dome directs water toward and out the drainage holes. Bi-level drainage holes encourage air to circulate in the bottom of the pot (photo, below).

rocks for drainage, not needed in pot with domed bottom

A 6″ pot with a domed bottom for better drainage.

In Saturated Soil

Capillarity helps hold water among the soil particles until roots can absorb it. But, if the roots can’t use that water, they can rot if the excess can’t drain away. This water fills the air pore spaces, cutting off air circulation around the roots. Soon, anaerobic decomposition begins and contributes to root failure.

Lavender must have good drainage.

A full pot of thirsty annuals in hot sun or a large leafy tomato might be able to absorb all that water, but plants that need less moisture will suffer. Lavender, rosemary, succulents, orchids, and other plants requiring perfect drainage can be damaged in saturated soil. For these kinds of plants, keeping them potbound (not overpotting), using terra cotta pots, watering less often, and placing them under cover during rainy weather will help.

In addition to those suggestions, add more plants to the container you want to use. More foliage dries the soil faster. Remove the mulch, at least until the young plants have grown. Before potting up, incorporate extra drainage material into the soil. This is especially important when using large pots.

Rocks For Drainage and Weight

I have used rocks for drainage on very few occasions. Businesses and schools hired me to fill concrete or ceramic planters. The extra weight of rocks prevented the pots from “walking away”. Amending the potting soil to facilitate drainage through the entire soil profile is the preferred method.

First, I covered the drainage holes with synthetic landscape fabric or a handful of polyester fiberfill. Then heavy rocks and gravel went into the bottom third of the large container. Instead of piling soil directly on top of the gravel, I added a layer of landscape fabric over the sloped surface of gravel and up the inside of the pot. Then I filled the space with soil.

Landscape fabric prevented soil from eroding into the gravel. Sloping the fabric, so water concentrated at a low point, helped remove more water from the soil, into the rocks, and out the drainage hole.

Sometimes I added rocks and/or charcoal for drainage when planting houseplants in decorative containers without drainage holes. Still, we should check for accumulating water and tip the planter on its side to let stagnant water drain out. Or use a dry wooden dowel to periodically test for moisture.

Otherwise, I never add rocks for drainage in a pot.

New Gardens For a New Property: What To Do First

Dec14

2021

A New Home and New Gardens!

View from the front porch.

As you might know from reading The Farm In My Yard, I moved from Rockville, Maryland to Charlotte, North Carolina in 2013. I worked for a few years, while watching over my elderly mother. After she passed away in 2020, the search was on for a larger property in a smaller town. Must-haves included reasonably quiet surroundings, lots of nature, room to play in new gardens, and no HOA. This article includes information from a landscaper’s perspective that might be new to first-time property owners.

Success! In late October, I moved to a new home in northern North Carolina. A few obstacles didn’t stop my tireless realtor, Erika, from finding this (almost) perfect little house. There was Covid, for one, and the reluctance on the part of homeowners to list their homes for sale. Very few livable offerings in my price range came to the market. As soon as they did, they immediately went under contract.

As many buyers have done in this tight market, I made an offer on the property sight unseen. Well, truthfully, I did drive by the house before submitting an offer, and liked what I saw. Trees, woods, space, and sunlight—perfect for a gardener! The previous owners made some major improvements, saving me the trouble and the expense. But I had no idea what the interior looked like.

Inspections

When buying a house, have all the inspections done before closing, as recommended by your realtor or for your own peace of mind. Estimate the cost of necessary upgrades and repairs.

Particularly for older homes, check the roof and electrical, plumbing, and HVAC systems. Look for water damage and mold, pests and wood rot, foundation issues, adequate insulation, storage space, and evidence of ongoing maintenance.

Negative findings could nullify a contract or provide a basis for negotiation between your realtor and the listing agent.

The Lay Of the Land

Small towns, farms, and independent businesses dot the landscape in this part of Wilkes County. Several vineyards and state parks attract visitors to these lovely rolling hills. Drive along any of the scenic roads, and new vistas open at every turn; the Blue Ridge Parkway is only half an hour away. Beautiful countryside!

The big oaks frame a sunrise.

My new home, a one-story house built in the 1940’s, sits on 1¼ acres of mostly level land. The view from the front porch looks over a field, a few houses, and downslope toward a small stream. Stunning sunrises greet me from that direction almost daily.

Most of the trees’ leaves have fallen from the massive limbs of the native white and willow oaks (Quercus alba and Q. phellos). A few of these trees tower over the eastern border of the property. In the summer, those toward the west will shade the house from hot afternoon sun.

The mighty oaks came first, judging by their size, and then the house. If I were to name the property, “Quercus Magnus” would seem fitting.

Preliminary Plans For New Gardens

There’s plenty of space for the berries and the vegetables to bask in the sun. Plenty of space to raise shade-loving perennials in the fenced enclosure north of the great oaks. And plenty of space for gardens that will support birds, bugs, bees, and butterflies.

Also, importantly, there’s room to grow plants to sell at the local farmers’ market, as I did in Maryland for 25 years.

After Moving In

Deciding what to do first depends on the season, your climate, and the condition of the house and gardens. Priorities often reflect our occupations or interests, so artists might first set up a studio while contractors organize tools in the outbuildings. Growing families might rank bicycle storage, a big kitchen, and an extra bathroom at the top of the list.

And gardeners? Well, we look at soil quality, existing gardens, and sunlight. This gardener prefers a large, mostly blank slate. Others call it a lawn.

In April, I’d be concerned about starting seeds for the market, getting the summer vegetables and flowers planted, and cutting grass. But it’s December now. The yard needs tidying, houseplants need to find their homes, and, of course, we must bake Christmas cookies. Not to mention, those boxes won’t unpack themselves!

Moving into a house that doesn’t need major repairs eases the stress. To be sure, there are some improvements that can and will be made, but nothing that needs immediate attention. Wouldn’t mind a new kitchen with a dishwasher, Santa. (Chocolate chip or almond crescents?)

Trees and Shrubs

Poor Pruning Practices

Walking around the property will highlight issues that need attention. Check the trees and shrubs for dead or broken branches, or call a licensed arborist for a professional assessment. There are some dead twigs way up in these oaks. A brisk wind shakes them loose, so the truck stays parked under the carport. Fortunately, that debris falls short of the house.

: Low branches that have been headed back.

: Some of the daily fallout.

I’ll hire an arborist to clean up the trees and remove branches that have been headed back. Heading back, or bluntly cutting off the end of a branch, causes many epicormic shoots to form. Those are new growing tips emerging from buds concentrated close to the cut. The shoots also can cover the length of the branch. Epicormic shoots have weak connections to the branch and, over time, most will fail and fall from the plant (photos, above).

Similarly, topping trees is, in my opinion, not recommended. Yes, it reduces the height, temporarily, but topped trees in winter are hardly natural-looking and not attractive (photo, below). They, too, drop twigs over an extended period of time.

An expert arborist might be able to undo the damage from heading back or topping. However, removing the tree might be the most economical solution. Research appropriate tree species for your property and where to plant them. Keep in mind that plants almost always achieve dimensions larger than those indicated on the label. Your local agricultural extension office can help. Check with botanical gardens and sources such as your state’s native plant societies.

A topped tree.

The Root Of the Problem

Trees planted close to the foundation can threaten its structural integrity. Consider having them removed.

The same ruthlessness applies to the wrong tree in any space. Keeping silver maples or weeping willows close to the house, septic system, or underground utilities begs for trouble. This is where an arborist or a well-informed landscaper can recommend more fitting species and a pleasing design for better curb appeal. Call 8-1-1 to have underground utility lines marked.

Constricted

Look for old stakes and wires still looped around trunks or branches. Wooden posts rot, but wire and synthetic rope from clotheslines, fences, and hammocks persist.

As trunks and branches grow in girth, they attempt to grow around the obstruction, cutting off the vascular system inside the bark. This results in the death of those parts of the tree that cannot receive water from the roots. Early fall color on isolated branches might indicate trouble, such as pests or physical constriction.

In the Maryland garden, a dogwood tree died for no apparent reason. After cutting it down and opening the bark in several places, I found plastic rope deeply embedded in the trunk a few feet from the ground. Although the damage appeared several years after I had moved there, it eventually killed a beautiful dogwood.

Flares and Girdling Roots

: Flare on an old oak tree.

: Girdling root on maple tree and no trunk flare.

Most trees flare out where the trunk descends into the ground. If this flare is missing, see if soil has been piled up against the trunk, and remove it.

Construction around unprotected trees can deposit soil that cuts off the oxygen supply to the roots, resulting in the plant’s decline. As little as an additional 1-2″ can damage trees. Also, parking vehicles over the root system compacts the soil, impeding air and water penetration. Keep in mind that tree roots extend well beyond the dripline, or the edge of the canopy.

Check for a girdling root crossing over the trunk at the soil line or below it. As it grows, the root will hinder growth of that section of the trunk, making the trunk look straight-sided where it enters the ground. Cut it out before the tree tries to grow around it. Maples and other surface-rooting trees are notorious for this.

There’s no flare at the base of this maple tree (photo, above) and at least one large girding root is constricting the flow of water and nutrients from the soil. I noticed large dead limbs in the canopy, so the tree might be removed.

English Ivy

English ivy growing up an oak tree.

Vining English ivy (Hedera helix) is growing up a white oak’s trunk, using rootlets to cling to the bark. All the vines will be removed for 4 main reasons.

First, English ivy is a woody vine, so its stems will grow in girth just as a tree branch does. As they wrap around the tree trunk or the limbs and thicken over the years, the ivy stems will constrict tree growth, killing limbs and possibly the tree.

Second, the evergreen ivy holds moisture and debris close to the bark, and could encourage insects and diseases.

Third, as ivy scampers over the ground and up the trees, it provides safe haven for rodents. Birds of prey and other predators cannot see them. Here’s a red-shouldered hawk perched in a dogwood tree, looking for dinner.

Fourth, ivy competes with small native plants, crowding them out.

So the ivy must go.

Headings

Page 1: A New Home and New Gardens! (Inspections), The Lay Of the Land (Preliminary Plans For New Gardens), After Moving In, Trees and Shrubs (Poor Pruning Practices, The Root Of the Problem, Constricted, Flares and Girdling Roots, English Ivy)

Page 2: The Lawn (Safety First, Less Grass To Mow, Grass Clippings, Spontaneous Combustion), Drainage (Hold the Water), New Gardens for Old Plants (Virginia Sweetspire), More New Gardens and Less Lawn (The Black Walnut, The Ravine and the Woodland, Passionflower and Phlox ‘Minnie Pearl’)

Page 3: Planting a Few Trees (The Rule Of Thirds, Too Cold To Plant New Gardens?, Viola, Different Players—Same Script, All Those Leaves), A Welcome Surprise (A Firm Foundation, Heeling In, Iris, Chores Indoors), Christmas Already?, and Concluding

Return to the top of Page 1

Pages: 1 2 3

How To Transplant Houseplants

Aug27

2019

Time To Transplant Houseplants?

As the end of the growing season approaches, we need to prioritize all the chores that need attention. Do the houseplants require transplanting? The plants that summered outdoors must come back inside soon, before frost damages the foliage or kills the plants.

They’ve been luxuriating on the porch, in higher humidity and brighter light than they usually receive inside. It’s no wonder they look fabulous! So, reintroduce them to indoor conditions while the days are still somewhat long and before the furnace kicks on and dries the air.

Perennials that looked picture perfect in May now look a little stressed after those record high temperatures. And the tired vegetable garden needs fresh compost or aged manure before setting the fall crops.

In a few weeks, flowering bulbs will arrive at garden centers…with pansies, violas, snapdragons, dusty miller, and Heuchera, trailing ivy, and hardy grasses. You’ve been dreaming of those beautiful combination planters, like the ones you saw last autumn at the garden center. But first things first.

Should We Transplant Houseplants Now?

Let’s start with the houseplants. Exposing tropicals to cooling temperatures outdoors, as autumn takes hold, could stress your houseplants. And some of those plants are pleading for attention right now.

While certain plants can tolerate cooler temperatures (cyclamen, ferns, English ivy, succulents, ponytail palm), others can’t. The aroids (peace lily, Dieffenbachia, Anthurium, Philodendron, Alocasia, Chinese evergreen, pothos), prayer plants (Calathea, Maranta), and some of the begonias, for example, should come indoors before temperatures dip below 60°F.

Although they won’t be killed by a few nights in the 50’s, or even the 40’s, you don’t want to prolong their discomfort. Chilling stresses many of our tropical houseplants, and can rot roots and disfigure foliage.

Inspect Them First

Scale on Ficus neriifolia (leaves are 7/16″ wide).

You probably won’t need to transplant houseplants, summering on the porch, that were repotted in the spring. All you need to do now is to inspect them for insects and spider mites before bringing them indoors. Check the bottom of the pot for slugs and sowbugs hiding around the drainage hole.

Clean up the leaves, too, and remove any that are discolored, insect-eaten, or damaged. Peel away the entire leaf, so none of the leaf stems (petioles) remain that later will turn yellow or brown.

After the inspection, clean the pots, wash the saucers, and place the plants in front of the windows where they seemed to thrive last winter.

Horticultural Oil

The dwarf Ficus neriifolia contracted a scale infestation, so I sprayed it with a horticultural oil solution. For insects and mites, horticultural oil works very well. It smothers the pests and is safe to use on most plants, including edibles.

Wiping the horticultural oil solution on smooth leaves (fiddle-leaf fig, pothos, peace lily) with a soft sponge removes dust, grime, and residue from water and fertilizers. It gives them a nice luster without appearing artificial. Read the label; I prefer to use less oil than is recommended on the label—to start with, anyway. Horticultural oil makes surfaces slippery, so be careful.

The fiddle-leaf fig, Ficus lyrata.

**Do Your Houseplants Actually Need Bigger Pots?**

Evergreen bonsai.

Knowing if the plant needs repotting, when to repot, and how large a pot to use is half the battle.

Does it wilt often? Perhaps instead of repotting, the plant needs to be deeply watered. Or maybe the roots have rotted in waterlogged soil, or the water rushes right through without moistening the soil.

I’ve seen a lot of dead plants over the years, and many simply were in pots that were too large. “Aren’t we supposed to transplant houseplants every year, just like our children outgrow their shoes every year?” No; once they have matured, plants can stay potbound for quite some time.

“If I transplant houseplants into bigger pots, won’t that make them grow faster and bigger?” No, another myth! If you transplant houseplants into pots twice the size they need, they more likely will die faster.

Large pots hold large quantities of soil and water. When the moisture is not used by the plant, the sodden mass just sits there, cutting off the oxygen supply and rotting the roots. So, if the entire volume is not tightly filled with roots, the plant doesn’t need to be repotted.

Many houseplants like being potbound. English ivy (Hedera helix), pothos (Epipremnum aureum), Philodendron, palm trees, Ficus trees, African violets, succulents, snake plants (formerly Sansevieria, now Dracaena), and bonsai prefer somewhat cramped quarters. Many potted herbs (rosemary, lavender, chives, sage, thyme) also fare better when potbound. But, in order to ensure good health, gardeners must provide nutrients according to the needs of the particular plant, and according to the time of year.

It’s helpful to know the habits and preferences for each kind of plant. For example, although the 4′ tall variegated snake plant (Dracaena trifasciata ‘Laurentii’) eventually will need a 10″ or 12″ pot, its cousin, the dwarf bird’s nest species (D. hahnii), can stay in a 4″ or 5″ pot for many years!

Fertilizing Houseplants

Most tropical plants spending the winter indoors won’t need fertilizer until late winter or early spring. If they continue to grow and look healthy, and they’re receiving good light, though, diluted solutions (1/4 to 1/2 strength) can be added every 4 to 6 weeks. Err on the side of using less fertilizer in winter.

As long as they’re properly watered and fertilized, your plants can remain perfectly happy while potbound. In fact, they’re easier to manage this way, since there’s less likelihood of overwatering. But you’ll have to water more frequently.

Look for products formulated for foliage houseplants or for flowering plants. They’re available in several forms: timed-release prills (use a low dose from fall through winter), liquids, granules, and soluble crystals. Read the label.

Fungus Gnats

Plants in smaller pots are less susceptible to diseases, root rot from overwatering, and fungus gnats. Ever have those annoying little “fruit flies” around your houseplants? The simplest remedy is to allow the soil surface to dry out.

Female fungus gnats lay eggs on moist soil. When the tiny larval worms emerge, they eat small roots, sap on cuttings, fungus, and organic matter in the top inch or two of the soil. Let the surface of the soil dry before watering again, and you’ll have fewer fungus gnats. See if adding a 1/2-1″ layer of pine fines as a mulch might prevent gnats from laying eggs.

Yellow sticky cards are good for catching flying insects. A card placed horizontally near the plants, on the pot’s rim, or in a sunny window attracts the most gnats.

Save the Spider!

A green spider plant.

The spider plant in the 4″ pot that your girlfriend gave you two months ago is literally crawling out of the pot. She propagated it from one of her own plants, so it has sentimental value.

Spider plants, related to other strong-rooted Asparagaceae (formerly Liliaceae) family members, develop roots that circle around the inside of the pot. The vigorously growing roots raise the entire plant higher in the pot, opening up air spaces around the root ball. This dries out the finer roots, and water gushes immediately through the drainage holes without moistening the soil. Clearly, it’s time to work on this one.

When Should I Transplant Houseplants?

A good time to transplant houseplants is in spring to mid- or late summer. Plants that recover slowly (for example, succulents) should be repotted, if needed, by mid-summer. In autumn and winter, plants receive fewer hours of daylight, photosynthesizing at a reduced level. Our slower growing tropicals don’t grow much foliage in autumn and in winter. And roots also are reluctant to grow.

Cooler temperatures, compared to the balmy summer days spent on the porch, cause systems to slow down. So, trying to force plants to grow at a time when they’re entering semi-dormancy often does more harm than good. Plopping a plant’s almost dormant root system into wet soil and expecting it to grow is asking the plant to do something against its nature. It would rather stay semi-dormant.

Providing a greenhouse atmosphere—warm, humid, and sunny—keeps your houseplants in much better condition, even through the shortest days of winter. Optimal light levels increase rates of photosynthesis, respiration, and transpiration. As a result, they might grow almost as fast as they did in June.

But most of us deal with dryer air, energy-saving chilly nights, and dim lighting (in the plants’ eyes) until the hyacinths bloom outside.

Plants, both indoors and out, take on renewed vigor once the days lengthen closer to springtime. Some of us humans do, too.

How Big Should the Pots Be?

Succulent dish garden in ceramic bonsai tray.

I’ve grown dwarf peperomias and miniature succulents, such as Echeveria minima and Haworthia truncata, in 2″ pots for many years. Since the succulents are prone to rot in wet soil, keeping them very potbound decreases the chances. There simply isn’t that much soil in the little clay pot, and it dries fast in direct sunlight.

Most of the succulents I enjoy growing are on the small side, anyway. Almost all are in 1½” to 4″ pots, and others have been planted in larger, but shallow, bonsai trays (photo, right).

I brought with me from Maryland a 4½” pot of Drimiopsis kirkii, one of the leopard lilies, and it has yet to be repotted into a larger pot, 6 years later. Its cousin, Drimiopsis maculata, however, grows from bulbs which multiply faster than those of D. kirkii. So D. maculata gets divided more often, but they’re still in 4½” pots.

Dracaena hahnii, the dwarf snake plant, lived happily for years in a 4½” pot. The small, glossy-leaved Spathiphyllum wallissii would have complained if it had been bumped up into anything larger than its 6½” plastic pot.

We’ve had this miniature cyclamen for years.

A pink flowering miniature cyclamen stays in its 4½” pot (photo, above), year after year. It is now coming out of dormancy and beginning to grow new foliage, contrary to what most other plants are doing. That’s because its growth cycle calls for cool to cold, but not freezing, temperatures in order to set flower buds. It will be fertilized accordingly, for a full canopy of marbled leaves.

The plant’s habit and its root structure help determine the required pot size. In general, transplant houseplants into pots that are only 1″ to 2″ wider, and only if they need it.

The Old Weeping Fig

Variegated weeping fig.

A weeping fig (Ficus benjamina), given time, will grow to the ceiling. Instead of raising the roof, its height can be managed by “aesthetically” cutting stems back in the spring, when it will respond faster.

I grew a variegated weeping fig in a 14″ pot for about 15 years, in front of a big window that received a few hours of morning sun. When the tree grew to almost 8′ tall, above the top of the window, I pruned it back a few feet. Then, when it regrew, all the foliage was once again in the sun and at eye level.

African Violets

A healthy African violet.

African violets (Saintpaulia ionantha) are happy to stay in 4″ pots for years. Miniature African violets need smaller pots than that.

A rule of thumb for pot size and an African violet is to plant it in a pot that is 1/3 the spread of the foliage. So, a 4″ pot will accommodate a plant that is 12″ wide. Plants in top condition might take a slightly larger pot, but you have to pay very close attention to moisture and soil drainage.

“What should I do with an African violet that has a long trunk?”

As these plants grow new leaves from the top of the rosette, older leaves lower on the stem die off. That’s part of their natural growth pattern. When the plant develops a trunk, it’s time to make an adjustment. But don’t do this if the plant is slowing its growth. Spring to mid-summer is a better time for this procedure.

Remove the plant from its pot and slice off the bottom third of the root ball. Shave off a small amount from the sides as well. Wash the pot, check the plant for insects (mealybugs, especially), and treat with horticultural oil if necessary.

Place a small amount of African violet potting soil in the bottom of the pot. These plants like peat moss in their mix. Set the plant in the pot, and fill in the sides with more soil, using a chop stick to firm soil in the gap.

Part of the trunk will now be loosely covered with soil, and it will grow new roots. The top of the root ball should be lower in the pot than it grew previously. (Yes, this is exactly what we don’t ordinarily recommend.) Water it in, using lukewarm (about 85°F) water. Keeping the soil too wet will rot the trunk and the roots.

Use the kitchen sink sprayer to wash soil off the leaves, using lukewarm water. Towel off the water drops, and let the plant dry in a warm location.

It’s less stressful for these plants if this is done every year or two, before the trunk grows a few inches tall. But I have seen perfectly happy violets with long stems curling over the edge of their pots.

“What are those marks on the leaves?”

Water the soil—always lukewarm for African violets—and avoid wetting the leaves. If water splashes on the leaves, absorb it with a towel, and let the plant dry in a warm place. As drops of water chill on this plant’s leaves, unsightly tan or brown rings and lines will be left behind.

Grow African violets at 70 to 74°, and fertilize regularly with a product formulated for this genus.

Less Is More

Move miniature species of plants into something only 1/2″ to 1″ larger, if they need it. I know; that doesn’t seem like it could make much of a difference. But for the plant whose roots, in the wild, might be crammed between layers of sedimentary rock on a blustery cliff, 1/2″ is plenty.

Large-growing plants require new pots up to 2″ wider in diameter. Peace lily (robust varieties of Spathiphyllum), weeping fig (Ficus benjamina), Chinese evergreen (Aglaonema spp.), and larger palm species can be moved from 6″ starter pots into 8″ pots. And, importantly, this assumes that the roots tightly fill the smaller pot.

Many of the tropicals will survive and prosper over the next several months, even while very potbound. If they’re already in 8″ pots, they’ll likely be fine until spring, when they can be potted on if needed. The 6′ tall fiddle-leaf fig in an 8″ nursery pot, though, can go into a 10″ pot, since the heated sunroom has floor-to-ceiling windows. Sunny conditions encourage plants to grow new roots, but carefully monitor soil moisture. Avoid watering houseplants (especially succulents) on cloudy days.

If growing conditions in your home are not ideal, but plants absolutely need to be repotted, transplant them now, before fall, into slightly larger pots. Wait until spring to transplant large houseplants, if it’s needed at all.

Houseplants don’t require repotting every year. Once they have attained a mature size, they no longer need to be moved into progressively larger pots. Instead, regularly fertilizing with products formulated for houseplants will supply all the nutrients they need.

Headings:

Page 1: Should We Transplant Houseplants Now?, Inspect Them First, Do Your Plants Actually Need Bigger Pots? (Fertilizing Houseplants, Fungus Gnats, Save the Spider!), When Should I Transplant Houseplants?, How Big Should the Pots Be? (The Old Weeping Fig, African Violets, Less Is More)

Page 2: Prepare for Transplant (Root Insects, Speaking of Spider Plants, Roots-Air-Water-Light) and Potting Up (Score the Root Ball, Potting Soil, Begin Filling the Pot, Downsizing, Water It In)

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Lavender: History and How To Grow It

Apr17

2019

Lavender’s Long History

B.C.

For many centuries, lavender has enjoyed popularity for its alluring fragrance and for its medicinal qualities. Lavandula dentata was first cultivated on the Arabian peninsula, and other species spread from Greece across Europe. Lavender species might also have originated in the Cape Verde Islands and the Canary Islands off the west coast of Africa.

Thousands of years ago, Egyptians and Phoenicians used the herb in perfumes and during mummification. When Egyptian King Tutankhamen’s (1341-1323 B.C.) tomb was opened by Howard Carter in 1922, claims were made that the scent of lavender could be detected.

Greek traders introduced lavender around 600 B.C. to the Hyères Islands, off the southern coast of France, and to Europe from there. Ancient Greeks used it for insomnia and backache, and in public baths.

Other healing qualities of lavender were recorded in the 3rd century B.C., when Greek physician/philosopher Theophrastus (c. 372-287 B.C.) wrote of them in Concerning Odours.

Cleopatra (69-30 B.C.), Queen of Egypt from 47-30 B.C., was able to temporarily preserve her kingdom from Roman rule. As the story goes, she used lavender to win the love of Roman generals Julius Caesar (100-44 B.C.) and Mark Antony (83-30 B.C.).

Upon defeat by Augustus Caesar (63 B.C.-14 A.D., first Roman emperor from 27 B.C.-14 A.D., and heir of Julius Caesar) and Cleopatra’s death by suicide, Egypt then became a Roman province.

Early A.D.

Mary is said to have used lavender when Jesus (4 B.C.-30 or 33 A.D.) was an infant and again when he was crucified. Both the Bible and, later, William Shakespeare’s (1564-1616) work The Winter’s Tale, refer to the herb as “spikenard”. Ancient Greeks called lavender “nard” or “nardus”, apparently after Naarda, a city in Syria where it was sold.

Pliny the Elder (23-79), Roman naturalist and encyclopedist, described relief from “women’s problems” attributed to lavender. His great work, Naturalis Historiae, is composed of 37 volumes, describing natural sciences from agriculture to mineralogy to zoology. Dioscorides, the Greek physician under Nero (37-68), collected herbs and, in 77, wrote about their uses in De Materia Medica.

When the Romans invaded England in 43, they used the lavender they brought with them for bathing, cooking, and giving scent to the air. The Romans and the early French believed in its antiseptic properties, and used it to treat infections and to heal wounds.

It is no surprise, then, that lavender derives from the Latin root lavare, meaning “to wash”. And when the Romans departed England around 410, this plant was left behind, growing in gardens around monasteries.

It’s Debatable

Much information online refers to the introduction of lavender to England as late as the 16th century. But as important as this herb was in Roman culture, and because other references claim that they did indeed bring it with them when they invaded England, I will leave it there…unless I find information that clarifies the debate.

From the Middle Ages Forward

During the Dark Ages, from the late 400’s to 1100, lavender wasn’t used much outside the monasteries. An edict issued by the Holy Roman Empire in 812 ordered monks to grow vegetables, medicinal herbs, trees, and flowers. Lavender was grown at Merton Abbey, near the center of production in Mitcham, in Surrey, England. According to records from 1301, Merton Priory sold lavender to raise money for King Edward I (1239-1307).

Medieval and Renaissance women who worked by taking in laundry used the herb to scent it when washing and also when drying the laundry on top of lavender shrubs. In 12th century England, washerwomen using the herb in this manner were called “lavenders”. Incidentally, the word “laundry” derives from the same root, the Latin lavare.

Monks cultivated it in monasteries as a medicinal herb during the Middle Ages (in European history, approximately 500-1350). A German nun named Hildegard of Bingen (1098-1179) used lavender water with vodka and gin for relief from migraine. And French King Charles VI (1368-1422) slept with lavender-filled pillows.

From the Renaissance

Fit For a Queen Or a King

King Henry VIII.

English King Henry VIII (1491-1547) destroyed the stone monasteries and their medicinal herb gardens in the 1500’s during the religious purges. Because this plant is not native to the area, remaining specimens of lavender were found primarily in private gardens.

King Henry’s daughter (with Anne Boleyn), Queen Elizabeth I (1533-1603), enjoyed lavender conserve, a type of jam, and fresh flowers every day. She sought relief from migraines by drinking an herbal tisanne containing lavender.

King Louis XIV (1638-1715) of France bathed in scented water. Around this time, lavender was used to treat headaches, nervous conditions, insect bites, mad dogs, and snake bites. And if people needed their passions stirred, they just tied some stems to the bed post!

And For the Rest Of Us

Merchants traveling along the Silk Road, from central Asia to Europe, inadvertently carried the Black Death with them. Bubonic plague spread across Europe from 1346 to the early 1350’s, killing one-third to possibly 60% of the entire population.

Infected fleas on rats transmitted the Yersinia pestis bacterium to people initially through flea bites. But modern researchers now think transmission was airborne, particularly among crowded populations. Outbreaks of the plague were treated with lavender as an antiseptic, but its efficacy is questionable, especially against such a virulent microbe.

Lavender Makes Good Business Scents

Sixteenth century glove makers in Grasse, France, used lavender to scent their wares. I can’t judge the accuracy of the claim, but it was said that those who made or wore the gloves were spared the agony of plague and cholera.

The Shaker community was the first to commercially cultivate lavender in the area now known as the United States and Canada, in the 1600’s. They used it to treat hyperactivity, flatulence, insomnia, and to fight bacterial and fungal infections. Their products that sold in distant markets included candles, cleaning products, soaps, and treatments for bee stings, migraines, burns, restless sleep, and skittish horses.

In another European epidemic in 1664-5, many died from the Great Plague. Lavender sold for high prices and was in demand for its supposed ability to ward off infection and to repel insects. People wore bundles of the herb on their wrists. Burglars of the ill took precautions by washing in Four Thieves Vinegar, containing lavender, garlic, and vinegar, to prevent infection. And those criminals who were caught and sentenced to digging graves also washed in the vinegar.

Seventeenth century herbalists John Gerard and Nicholas Culpeper wrote about the benefits of lavender. Gerard prescribed it for palsy. A few decades later, in 1652, Culpeper recommended it, in The English Physician, “for all the grief and pains of the head”.

Ornamental Use

In 17th century Ireland, lavender was planted as a low clipped lawn. Later, in the mid 1860’s in County Down, Sir Arthur Rawdon’s Moira Castle maintained an acre of lavender lawn. John Reid, in 1766, recommended lavender as an ornamental walkway edging in The Scots Gardener.

The Victorian Era

Queen Victoria.

Both Queen Victoria and Queen Elizabeth I, hundreds of years before her, used herbal products supplied by Yardley and Company of London.

Britain’s Queen Victoria (1819-1901) popularized lavender from its use as a deodorant, and floor and furniture cleaners. The Queen appointed Miss Sarah Sprules “Purvey of Lavender Essence to the Queen”, and used it everywhere and as a cure-all.

As a strewing herb on floors, it gave out a fresh scent when walked upon. Women sold bundles of lavender, called Tussie mussies, on the city streets. The scent became synonymous with purity and cleanliness.

In 19th century Provence, France, lavender treated dizziness, nerves, convulsions, stomach ailments, infections, palsy, and repelled fleas and other insects.

Lavender is still used in dried flower arrangements, pot pourri (flowers and buds), and sachets (for fragrance and to deter moths). Bath products, candles, and perfumes sold today attest to lavender’s enduring qualities.

Too Much Lavender?

Lavender’s overuse contributed, consequently, to loss of its popularity in the early 1900’s. It also became associated with “old ladies”, although during World War I, medics dressed soldiers’ wounds with it.

And then, in the 1920’s, French perfumer Rene Gattefosse severely burned his arm. He immediately plunged it into a vat of lavender oil, the story goes, and experienced immediate pain relief and, according to some, rapid healing. His book, Aromatherapie, describes applications for wounds and other uses derived from essential oils, and gave rise to…you guessed it…aromatherapy!

In the Medical Establishment

Whatever your beliefs—whether lavender’s popularity is due to its use as a panacea or as a wonderfully fragrant plant—it is beautiful in a sunny garden and it attracts bees, butterflies, and other pollinators.

There are only a few scents that come close to lavender on my list of favorites. But, on one of the “favorite smells” lists online, this scent rated #49! And “petrol” rated…#1! Bacon, freshly-baked bread, rain, cookies in the oven, and mowed grass made the top 10 in some of those lists. But…49th?!

Caution!

The U.S. National Institutes of Health recommends that pregnant or lactating women not use lavender on their skin or take it internally, because the side effects are unknown. For sensitive people, it can cause skin irritations, and can be toxic if consumed.

In prepubertal boys, gynecomastia, an enlargement of the breasts due to hormonal imbalances, can be caused by topical lavender products.

One research study claimed that attaching a pad dipped in lavender oil to the neckline of clothing reduced the risk of falling by 43% among nursing home residents.

Testing for its use in treating cankersores and insomnia resulted in insufficient evidence for its efficacy…

…But let me tell you a little story

One spring day at the garden center, I was working on lavender topiaries and large specimens—reshaping, cutting back, repotting, and removing all the dead leaves. The scent was just wonderful. It took a couple of hours to clean up all the plants, and then it was lunch time.

As always, I spent the time in my truck, reading and listening to the news while enjoying my lunch. Well…that day was the closest I had ever come, in the past 4 decades, to falling asleep while at work. I had to fight to stay awake!

Normally skeptical of proclaimed powers of plants, I believe this one—that the scent of lavender can induce sleep! No wonder it has been found in bath products for thousands of years.

Edible Lavender

Lavender has been used fairly extensively over the centuries, in conserves, teas, vinegars, and pastries. One of my herb books describes lavender as “an acquired taste”. I made lavender tea, once. Only once.

Apparently, L. a. ‘Munstead’ is the most popular variety for cooking and baking, for its sweeter fragrance and “citrusy notes”. Those seeking new culinary experiences might find lavender in salads, dressings, pasta, sauces, and desserts. If I remember correctly, it was at the Olney Farmers’ and Artists’ Market, in Maryland, where, years ago, I purchased a lavender bud and lemon poundcake that was delicious.

Lavender flowers.

The Lavender Genus

Lavender is a member of the mint family, Lamiaceae, and is related to basil, thyme, rosemary, Swedish ivy (Plectranthus), ajuga, Phlomis, and all the salvias, including sage. Their lipped flowers appear in whorls, on spikes carried above the foliage. Flower colors range from white and pink, to blue, lilac, violet and blackish purple. Some species in the family have yellow flowers.

The stems of plants in this family are usually, but not always, square in cross-section. Lavender’s resemblance to rosemary has confused many gardeners, but the scent distinguishes one from the other.

There are 47 known species in the genus Lavandula. Leaves are generally simple (with a smooth, or “entire” margin) or dentate (with a toothed margin), although some species have pinnate leaves (L. buchii, from the Canary Islands). Leaves and other parts are covered in trichomes, the fine hairs (the indumentum) from which essential oils are harvested. L. lanata (from Latin lanaius), the woolly lavender, is covered in woolly hairs.

Most gardeners associate this genus with silver or gray foliage, but it includes some green-leaved species as well. Also available are variegated cultivars, such as ‘Platinum Blonde’, whose leaves are edged in creamy white.

Lavender From Seed

‘Ellagance Purple’ seedling.

Lavenders are small and shrubby in their growth habit, and qualify as woody perennials or as sub-shrubs.

Some will bloom in the first season when grown from seed, and, where they don’t survive the winter, would be considered annuals. I used to grow a variety called ‘Lady’, which had a powerful scent.

A new English lavender called ‘Blue Spear’ will sprout in 2 to 3 weeks from seed, after first being chilled for a week in the freezer. It will perennialize in zone 5 or 6, but can be grown as an annual flowering plant in colder regions. Seeds have to be started very early, though, or the previous fall, for blooms from late spring through summer. ‘Blue Spear’ is an upright plant, growing 11″ to 14″ tall and a bit narrower than that.

***Update***: This summer, I’m growing a variety of lavender from seed that blooms the first year if the seeds are started early in the season. ‘Ellagance Purple’ has dense spikes of deep purple flowers. So far, they look healthy in their 2½” pots, but I’m not sure they’ll have enough time to bloom this year. Photo shows how long the roots are compared to the stem. 7/20/2022

Perennial Species

Cross-pollination among the species and varieties gives rise to more variation. Cuttings taken from desirable plants (asexual or vegetative propagation), however, assure the grower that all the young cloned plants will look the same. Many newer cultivars are under plant patent protection, and may not be propagated without authorization from the patent holder.

Their common names also vary widely. The English types are well-defined, but when it comes to French or fringed, Greek, Italian, or Spanish, there doesn’t seem to be universally accepted agreement concerning the species they’re assigned to. When shopping for plants, refer to the name of the cultivar (‘Hidcote’, ‘Provence’, etc.) to avoid confusion.

Lavandula angustifolia

Zones 5-8. Formerly L. officinalis. Commonly called English lavender, this species grows well there but is native to France, Spain, and Italy. It is used more often in cooking than other lavenders, due to its lower camphor content. This species’ essential oils are considered superior to those of other species. Earlier blooming than lavandins, generally.

Varieties include:

‘Blue Spear’: zones 5 or 6 to 8 or 9. 11″-14″ tall, upright growth; deep blue substantial flowers, will flower first year from seed.
‘Ellagance Ice’: compact; large silver-white-light bluish flowers all summer.
‘Ellagance Purple’: zones 5-7; deep purple flowers on full spikes, blooming first year from seed.
‘Hidcote’: 12″-18″ tall; tightly budded stems; flowers deep purple.
‘Jean Davis’: 18″ tall; light pink flowers.
‘Melissa’: 24″ tall; pale pink to white flowers late spring to early summer.
‘Muntsead’: heat, sun, and humidity tolerant; 12″-18″ tall; late spring to early summer flowers from pale blue to shades of purple.
‘Platinum Blonde’ (‘Momparler’): zone 5b. To 18″ tall, culinary. Creamy white leaf margins.
‘Royal Velvet’: 2′ to 2 1/2′ stems; velvety purple/navy blue flowers that retain color when dried.
‘Sweet Romance’: 12″-18″ tall; purple flowers early summer to fall; a Proven Winners cultivar.

Lavandula x intermedia

Zones 5-8. Often called Lavandin or Dutch lavender, this species is a cross between English lavender (L. angustifolia) and spike lavender (L. latifolia). Flowers have abundant nectar, and contribute to the sought after monofloral honey. These interspecific hybrids, denoted by the lower case “x” in the species name, are sterile and cannot set viable seed.

Varieties include:

‘Fred Boutin’: to 3 1/2′ tall. Late summer light blue blooms.
‘Grosso’, also called ‘Fat Spike’: about 3′ tall and wide; very fragrant; medium violet blue flowers. Grower Pierre Grosso (1905-1989) discovered this variety in the Vaucluse district of France. It has a very high oil content, and is disease resistant.
‘Hidcote Giant’: to 3 1/2′ tall. Dense, dark purple flowers, dries well.
‘Phenomenal’: zones 5-9; grows 2′ to 4′ tall and wide. ‘Phenomenal’ is more heat, humidity, and drought resistant than others. Introduced by Peace Tree Farms, 2012.
‘Provence’: from southwest France; foliage grows 2′ tall with very tall spikes of pale purple flowers in early summer to early fall; culinary, and commercially grown for the perfume industry. One of my favorites for scent and for tall, see-through flower spikes.
‘Seal’: 4′ to 5′ tall! Strong fragrance, late summer blooms.
‘Thumbelina Leigh’: zones 5 or 6 to 9. A dwarf English lavender, growing only 6″ to 12″ tall, medium blue flowers. This selection comes from New Zealand.
‘White Spike’: to 3 1/2′ tall. Nicely contrasting white flowers, mid summer. Culinary.

Lavandula dentata

Zones 8-9. French or fringed lavender grows about 3′ tall; toothed edges (dentata, from Latin for tooth), light woolly texture; narrow spikes of long-lasting purple flowers beginning in late spring; from the Mediterranean region, Atlantic islands, Arabian peninsula.

Lavandula stoechas

Zones 8-9. (Pronounced stee′-kiss; [“oe” has long “e” sound, as in “amoeba”, and Greek “ch” has a hard “k” sound.] Derived from the Greek stoichas for “in rows”.) French, Italian, or Spanish lavender is a compact grower; feathery petals at tip of inflorescence, sometimes called “Butterfly lavenders”.

From France, Spain, Portugal, Italy, Greece; considered invasive in Victoria, Australia since 1920. Can self-seed. This was probably the species commonly grown in ancient Rome and Greece. Eucalyptus fragrance.

Varieties include:

‘Dark Eyes’: 2′ tall. Purple-red flowers May to autumn if deadheaded.
‘Kew Red’: zones 8 to 11. Red-violet blooms with deep pink bracts at tip. From southern Spain. Introduced by Kew Gardens, 1999.
‘Otto Quast’: 2′, prune for fullness. Reddish-purple flowers with deep pink bracts at tip.
‘Silver Frost’ (L. angustifolia x lanata): 2′ to 3′ tall, lax stems. Heavily felted silver foliage.

Lavandula pedunculata

Zones 9-10. Also known as Lavandula stoechas subspecies pedunculata. Spanish or French lavender has flowers high above the foliage, and long narrow petals on tip of flower; from Iberia, western Turkey, Morocco.

Photograph above: field of lavender at Notre-Dame de Sénanque Abbey, southeast France, in the Vaucluse district of Provence near the village of Gordes. Established by Cistercian monks in 1148.

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Headings

Page 1: Lavender’s Long History, B.C., Early A.D., From the Middle Ages Forward, From the Renaissance (Fit For a Queen or a King, And For the Rest of Us, Lavender Makes Good Business Scents), The Victorian Era, Too Much Lavender?, In the Medical Establishment (Caution!, …But let me tell you a little story), Edible Lavender, The Lavender Genus (Lavender From Seed), and Perennial Species (L. angustifolia, L. x intermedia, L. dentata, L. stoechas, L. pedunculata)

Page 2: How To Grow Lavender (On Location, Light, Soil, How To Improve Drainage, Lime and Gypsum, Shopping for Lavender, How To Plant, Watering, To Mulch Or Not To Mulch, Fertilizer, Pruning, Growing Lavender In Pots, Azalea and Standard Pots, Freezing Temperatures, Heeling In, Growing Lavender Indoors)

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