Gardening in Dry Shade

Most of us probably imagine shady spots in the garden as cool, moist places that we don’t have to worry about watering, but more often than not that isn’t the case. In my back yard, which is bordered by forest on 3 sides, I’ve planted shrubs and perennials between the lawn and forest on each side. Though it’s shady there, the shade isn’t dense because the slanting rays of the rising and setting sun are enough to keep most plants happy. The real challenge in these areas is the overhanging trees.

Some trees have such dense crowns that they can keep a light rainfall from reaching the ground. I have mostly hemlocks bordering my yard and these trees are so dense that it isn’t unusual for the soil under them to be perfectly dry after a drizzle. In fact, I have stood under them when it was raining quite hard in the past and didn’t feel a drop. This can be a problem, but there are solutions.

To start with I chose plants that could stand both shade and dry soil. Fortunately there are many shrubs and perennials from which to choose; Hosta, foxglove, native coral bells (Heuchera Americana), Astilbe, daylilies, wild ginger, and many other perennials will do quite well in dry shade. For shrub choices, Kerria Japonica, hydrangea, many viburnums, rhododendrons, and azaleas will do well. Many spring bulbs do well in dry, shady places, and many wildflowers, grasses, and ferns often prefer them. Many groundcovers like pachysandra, sedums and vinca will also thrive in dry shade.

I also thinned out some of the tree branches with a pole pruner. I didn’t want to cut the trees down or completely scalp them up one side, so I took my time and selected those branches which, if removed, would let a little more rain reach the ground. The result is that you would hardly know any branches had been removed and most of my plants now get watered even in a light rain.

Still, there is a lot of competition from tree roots so I water any dry shade areas deeply at least once each week, depending on rainfall. This is important; watering the entire area helps ensure that the tree roots aren’t soaking up every drop of moisture from the soil that your plants are in. Trees also soak up nutrients, so I make sure any plants under them are well fed, giving them a good side dressing of compost in addition to their regular fertilizing.

The secret (if there is one) to growing plants in dry shade is to first read about the plants you’d like to grow there. Obviously, if the plant you have chosen prefers soil that is constantly moist you wouldn’t plant it in dry shade unless you didn’t mind watering every other day. Knowing what conditions plants require and giving them just a little extra attention means you can grow quite a large selection in dry shade.

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Powdery Mildew

Powdery mildew is a caused by any one of over 1600 species of fungus and makes leaf surfaces appear as if they had been dusted with gray or white talcum powder. Most species of fungi that cause powdery mildew are host specific, which means the mildew on your lilacs won’t attack your squash. The fungus produces mycelium (fungal threads) that grow on the surface of the plant but don’t invade the tissues themselves. Fungi feed by sending haustoria, or root-like structures, into the epidermal (top) cells of the plant.

Powdery mildew thrives when days are warm and dry and nights are cool. Cool, shaded areas where air circulation is poor and humidity is high are perfect breeding grounds, so susceptible plants should be planted in full sun far enough apart for air to circulate freely around them. Powdery mildew does not need a wet leaf surface to grow, but overhead watering raises humidity and can splash spores from infected plants to healthy plants, so watering should always be done from below, as with a soaker hose. Applications of high nitrogen fertilizer in late summer should be avoided because mildew prefers young, tender growth.

I have phlox and lilac that get infected each year but still bloom well the following season, so I don’t get overly concerned with powdery mildew. As an experiment, this year I planted a mildew resistant variety of tall phlox called Blue Boy, which so far hasn’t shown any signs of mildew. Pruning a few stems from the center of non resistant plants with dense crowns will increase air circulation.

The fungus does far more damage to vegetables than ornamentals and can spread quickly through squash, melon, and cucumber beds.  Planting mildew resistant varieties and pruning infected leaves from plants at the first sign of infection will go a long way in controlling the fungus.

Sprays can also be used for prevention and control. Studies by scientists in Brazil show that a spray made of 1 part milk to 9 parts water reduced the severity of powdery mildew infection by 90% on squash plants. Weekly applications have been shown to work well.

Another spray is made by mixing 1 tablespoon of baking soda, 1 tablespoon of vegetable oil, and 1 tablespoon of liquid dish soap in 1 gallon of water. Spray weekly, preferably on overcast days to avoid burning leaves.

Neither of these sprays will kill existing powdery mildew, but they will prevent its spread.  The disease can complete a cycle in as little as 72 hours, so it is important to inspect plants regularly and begin spraying at the first sign of infection.

Since the fungus over-winters on plant debris and in dormant bud scales, sanitation is an important part of control. All infected plant debris should be removed from the garden in the fall and destroyed. Never put infected plant debris in a compost pile.

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Weekend Wandering

I spent Sunday afternoon going from place to place to see if the fall sales had started and if nurseries were stocking spring flowering bulbs too early. Soil temperatures are still too warm to plant bulbs. If stored they need to be kept in a cool, dry place because sitting out on warm shelves until it is cool enough to plant them means they will have suffered.  At the Big Box Store I found bins full of bulbs sitting in 80 degree heat and high humidity. Squeeze those bulbs before you buy them-they should be firm, with no soft spots and no green top growth.

I didn’t find any bulbs at Agway but found that the canning supplies were in, so if you’re into canning now is the time to pick up new jars and lids.

I also found that they were having a sale on perennials; buy one at full price and get the second for half price, except new arrivals.  Sedums like Autumn Joy were selling by the cart load, and that’s no exaggeration. If you’re looking for sedums, you might want to get them soon.

Instead of sedums, I bought two Hostas. (Those who know me will think I’m crazy-I have over 200 now.) One of them is “Sum and Substance,” which I don’t have.  With its plain chartreuse leaves this isn’t the showiest of Hostas, but it is one of the biggest.  Plants can get up to 6 feet across with huge leaves measuring 9 or 10 inches wide and 2 feet long. The leaves are also deeply veined and that, along with their size, will make them ideal candidates for casting in concrete.

The other Hosta I bought is one I already have, called “Fragrant Bouquet.” Though the leaves aren’t anywhere near the size of those on Sum and Substance, the plant itself gets quite large; the one I have is at least 3 feet across. I like this one because it blooms later than any other Hosta in my yard and the large white flowers are very fragrant. The cream edged, apple green leaves are interesting as well.

My main reason for buying these particular Hostas though, is their sun tolerance; both will stand full sun. Though my new shrub border doesn’t get full sun it does get an hour or two of very hot, late afternoon sun. Any Hosta with blue gray leaves is out of the question here because hot sun melts the waxy coating on the leaves and they look terrible by the end of August. 

Plant prices are falling and now is the best time of year to plant, so it’s time to go shopping.

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Use Desire Lines When Planning Pathways

Where two sidewalks join in a 90 degree “L” shape quite often you find that people, instead of following one sidewalk to the end and then turning onto the other, have instead created a well worn path between the two legs of the L, so the result forms a triangle. This well worn path is called a desire line, also known as a social trail or desire path.

First coined in 1958 by French scientist, philosopher, and poet Gaston Bachelard in his book The Poetics of Space, the term desire path is now used by landscape architects to describe “a path that isn’t designed but rather is worn away casually by people finding the shortest distance between two points.”

Once we find the shortest path between two points we will use it over and over again. Many believe that interstate 95 between Boston, MA and Providence, RI follows a desire line worn away by many years of Native American travel.

Though its origin isn’t known there is a story of a landscape architect who, when laying out a university, didn’t put in any pathways. Instead he put in lawns and let the students find their natural desire lines.  Once these lines had worn through the sod, the architect had workmen install paved pathways where the desire lines appeared. 

If we pay close attention most of us will find that we have created desire lines in our own yards, even if the sod hasn’t worn through. The path taken to the tool shed, compost pile or vegetable garden is probably used again and again and is most likely the shortest distance between the house and whatever outlying point we wish to reach. If we decide to lay out paved pathways through our yard and gardens, we should always be aware of these desire lines and use them as much as possible in our plans.

Studies have shown that our penchant for straight lines is so strong that even when an obstruction is placed in our path we will simply go around it and return to the original straight line, so this should also be considered when planning a winding path. There should always be an obvious and valid reason for curving a path, such as a tree, shrub, or other object that breaks up the straight line naturally, without appearing artificial or contrived.

 

 

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Fall Planting

People who grow houseplants and pay close attention to them will notice that, in mid to late February, they begin to grow quickly. What triggers this growth spurt is day length. The sun shining for longer periods each day slowly wakes plants from dormancy. Because they grow so fast during this period, they need more water and nutrients.

Six months later in mid to late August, the opposite happens. As days grow shorter, plants begin to slowly prepare for their winter dormant period.  Above ground growth slows and though they still need water, plants begin to reduce their nutrient intake. This is why all fertilizing of trees, shrubs, roses and perennials should stop by mid August.  This is also why mid to late August is an excellent time for planting trees, shrubs, and perennials.

Because plants don’t exhaust themselves by putting all their energy into growing foliage at this time of year their energy can be directed to strong root growth instead, and they become established much more quickly. As daytime temperatures cool and fall rains begin they will also need less watering. A shrub or tree planted during the heat of June and July may need watering every day but in late August once each week will usually do, and this greatly reduces a gardener’s work load.

An added bonus of fall planting is that many plants are on sale, so if you’d like more plants in your garden and want to cut the work of watering in half, now is the best time to plant.

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Let Your Plants Become Established

A Weigela I planted in May began to grow almost immediately after I planted it and has grown six or eight inches since. Most plants don’t display the same indifference to being planted though; many, if not most have to sit and “think” about their new home for awhile before they show any signs of growth. This “sitting and doing nothing” time is when the plant is becoming established, and though there isn’t much going on above ground, there is plenty going on beneath it.

A Black Lace Elderberry, eight feet from the Weigela and growing in the same soil and light exposure, waited two months to show any signs of life. Then suddenly, almost overnight, new shoots appeared all over it. A Bottle Brush Buckeye, loaded with flower buds when I planted it, has sat quietly for three months. Though it looks perfectly healthy, it has shown no signs of new growth and the flower buds have yet to open.  A Kerria Japonica in the same shrub border began to drop leaves almost immediately after I planted it. I suspected transplant shock, but kept it moist and otherwise let it be. Now, almost four months later, it has quite a lot of new growth and even three or four flowers.

Despite their differing responses to their new home I left all of these shrubs alone because I knew they were busy establishing root systems. Different plants grow their roots at different rates, and if I had become impatient and moved those that seemed to sit and do nothing I would have had to let them become established all over again. My impatience would have meant waiting months longer.

I rarely move a shrub or tree that I have planted or transplanted until at least a year has passed. If I have watered and otherwise cared for it and it hasn’t shown any signs of growth by the end of its first full year, then I’ll consider moving it. Until then patience is called for because at times, the best thing for a gardener to do is nothing at all.

 

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Casting Leaves in Concrete

Why cast leaves in concrete? Well, why not? It’s fun, easy, and relatively inexpensive to do and when you are done you have a piece of garden art, a stepping stone for a path, or a small bird bath. You can use any large leaves like hosta, cabbage, rhubarb, burdock, or what have you. Some plants with huge leaves make dramatic castings and can be used as planters. They can even be painted to appear life like.

A friend told me about this a few months ago, so I thought I’d give it a try. The biggest expense is the bag of concrete, but that is less than $11.00 and you can make several castings with one bag. I use Quickcrete vinyl concrete patch because it dries fast and leaves a smooth finish. Some people also add coloring agents and fortifiers, but each extra item you add adds to the cost. The castings seem strong enough without concrete fortifier.

 

In addition to the concrete mix I used plastic wrap, something to mix in, something to stir with, rubber gloves, a dust mask, water, and a large pile of moist sand. Sand can also be bought in bags if necessary.

 

Here I’m using a hosta leaf. Since the ribs and veins are more prominent on leaf undersides, I put the leaf face up on the sand. To cast a leaf you need to think in reverse; if you want a bowl shape lay the leaf over a mound of sand. For an arched leaf casting, make a depression in the sand, and for a flat casting, level the sand.

 

Once I had the sand molded the way I wanted it, I removed the leaf and put plastic wrap over the sand. This keeps the sand out of the concrete and lets you finish the edges of the leaf.  The leaf should be face down on the plastic wrap before adding the concrete.

 

I mixed the concrete to a toothpaste or brownie mix consistency by adding water slowly so it didn’t become too soupy. Soupy mix will run off of the leaf. When I had the concrete mix at the correct consistency, I put some in the center of the leaf.

 

What is shown in this picture will be the underside of the finished casting. With my hand, I patted down and worked the concrete mix from the center of the leaf out toward the edges as shown. This is where the rubber gloves come in handy. The finished casting should be about 3/8 to 1/2 of an inch thick in the center and slightly thinner at the leaf edges. If it is a little thicker it will just take a little longer to dry. According to what I’ve read, the concrete on very large leaves should be up to about 1 inch thick.

If I wanted a casting you could hang, at this stage I would lay a loop of sturdy wire (like coat hanger wire) into the wet concrete and then cover it with more concrete. If leaves are bigger than 14 inches across it’s a good idea to reinforce them with wallboard tape or chicken wire at this stage so they don’t crack later on. Just lay the wall board tape or wire on top of the wet concrete and cover with more of the mix, smoothing as you go.

 

I gently pull the plastic wrap toward the leaf edges so the concrete mix doesn’t flow out beyond them. Peeking under the leaf as you pull the plastic wrap toward the center shows where the leaf edges are. This makes a nice clean edge. After I’m satisfied, I leave the casting just as it is shown for two days. If it’s supposed to rain, I cover it.

 

Once the concrete is dry, smooth surfaced leaves like hosta will peel away from the dry concrete easily. This picture shows the casting after about half of the leaf was peeled away. Hairy leaves like rhubarb or burdock may need to be scrubbed off with a wire brush after decomposing for a day or two. Some leaves might also stain the concrete slightly.

 

This is my first attempt at painting a concrete leaf that was cast earlier. It’s supposed to resemble a leaf from a green and white hosta variety known as “minuteman,” but for some reason this photo seems to have a bluish tint to it. Oh well-at least it shows what it is possible to do with leaf castings, and that’s the whole point. Next time I’ll use stiffer brushes and flat paint. This was done with foam brushes, which made getting sharp edges difficult. The satin paint also seems a little too shiny for my tastes.

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Shrub Trimming

I learned how to trim shrubs when I was handed some old hand operated hedge shears and told “go trim those shrubs.”  I protested, claiming truthfully that I had never trimmed a shrub in my life. “You’ll do fine,” my boss said, and then left, leaving a panicking 17 year old me behind. Since I had no choice I trimmed them, and found that it wasn’t that hard to do after all.  I’ve been trimming shrubs ever since.

Today when I teach someone to trim shrubs I have them watch me do it for a short time and then hand them some hedge shears and say “go trim those shrubs.”  Why? Because doing it is really the only way to learn how to do it.  Years ago, my boss knew that when he handed me the shears. 

When it comes to shrub trimming, most people have a fear of destroying their shrubs and it paralyzes them.  Trust me: You will not destroy your shrubs.  Many flowering shrubs can be cut right back to the ground and will grow back as bushy and healthy as ever. Granted, on your first and second attempt your shrubs may look a little lopsided, but so what- are you entering a shrub trimming competition any time soon? They will grow back quickly and you will have learned far more from what you might consider failure than you ever would have from a limited success.

The secret to trimming, if there is one, is visualizing how the shrub will look after it’s trimmed. Once you get that image in your mind you just trim a little off, stand back and look it over, walk around it, and then trim a little more off, making it look like the picture in your mind. You repeat the process until you’re satisfied. If you work slowly at first and pay close attention to the shrub, you will be able to see just where it should be cut.  Often, the shrub itself will visually guide you.

Michelangelo said when sculpting he simply released the figures from the stone, and that says a lot about what he saw in those blocks of stone.  That’s the way a shrub trimmer needs to see; not what is there, but what will be there.

Ninety nine percent of the battle is getting over the idea that you can’t trim a shrub. Once you’re over that and believe in your own ability, you’ll have all of your own shrubs trimmed and be asking the neighbors if you can trim theirs. Once you’ve reached that point, call me and we’ll talk about pruning; the last time I taught someone how to prune, the lady was pruning crabapple trees like an old pro in less than an hour and a half.

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Weekend Planting

I have a hill in my side yard that gets full sun all day. It’s actually more of a slight rise than a hill, but with a gravel base and full sun it’s a hot, dry spot where only the toughest plants like wild strawberry, thyme, and sheep sorrel grow. The area has always been a pain in the neck to mow, so over the weekend I bought a Russian sage (Perovskia atriplicifolia) and planted it near the top of the rise.

Russian sage is a tough plant that likes full sun and well drained soil. It can withstand drought and needs much less water than most perennials. Though the leaves smell a bit like sage when crushed it isn’t quite what we expect when we think of sage. It actually more closely resembles mint, with its square stems. It isn’t Russian either; it hails from Afghanistan, Pakistan, Tibet, and other parts of central Asia, but was named after a Russian diplomat. It is classified as a “sub shrub,” which is a plant that has both woody and herbaceous growth.  Herbs with woody stems like lavender and garden sage are also considered sub shrubs. 

Russian sage has very fragrant grey-green leaves on silver-white stems. Small blue-lavender flowers on tall, upright spikes cover the plant from July through September and give it a soft, wispy appearance. It blooms on new growth, so I’ll cut it back to about 6 inches in early spring. The variety I have reaches 4-5 feet tall with a 3-4 foot spread under optimal conditions, so if it likes its new home and does well, I’m going to plant a row of them as a small, informal hedge next spring.  

Since my “soil” here is nothing but gravel, I dug out a wheelbarrow full and then filled the large hole with a 50/50 loam and sand mix to ensure good drainage. Russian sage may be tough, but there are few plants that will grow in pure gravel. The plant can’t stand wet roots, so I’ll water it regularly until it becomes established and shows signs of new growth, and then gradually reduce watering.

With Russian sage as a background, other drought tolerant plants like yarrow, rudbeckia, and bronze ornamental grasses will be planted in front of it to cover the small hillside. All like the same sunny, hot, and dry conditions and the pink and yellow yarrows, yellow and magenta rudbeckia, and bronze grasses should all contrast well with the silver and blue Russian sage. Purple leaved sedums or purple-bronze ajuga might make an interesting, contrasting under planting for the taller plants as well.

Butterflies, hummingbirds, and especially bees love Russian sage, so it’s also a good plant to use to attract pollinators. Mine wasn’t in the ground more than a half hour before it was covered with bees, so if you aren’t getting the harvest that you expect from your fruits and vegetables, plant a Russian sage or two near them to attract more bees.

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