Calgary Horticultural Society: Gardening in dry shade 

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Gardening in the shade can be a challenge; gardening in dry, shady areas is even more difficult, and in the semi-arid climate in Calgary, shady gardens are often dry. Fortunately, it is possible to have a beautiful garden even in a dry shady spot, if you prepare ahead and choose your plants carefully.

First, it is always wise to assess the area. How much light does it get? Full shade is less than four hours and part shade is four to six hours of sun per day. How dry is the soil? Does it get moisture from rain or is it in a rain shadow, such as on the north side of a building or under dense trees or shrubs?

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In the most severe dry shade conditions, I don’t recommend any planting. Under the overhang of a building, where no sun or moisture can penetrate, and in full shade beneath shallow-rooted trees, especially Colorado spruce, it is often best to just put down a layer of decorative mulch.

One of the most common questions I am asked is “What can I grow underneath my spruce tree?” The answer I want to give is “Nothing.” Whereas that is not completely true, little will grow beneath spruce trees unless the area is watered very frequently. I don’t recommend trying; nor do I recommend removing the lower limbs of a spruce tree in the hopes of planting under the tree.

The most inspired solution I have seen to an overabundance of spruce trees was at a Calgary Horticultural Society Open Garden. The front yard was almost totally shaded by several spruce trees. The homeowner had covered the ground with a wood chip mulch, added a few beautiful containers of shade plants, and several gorgeous sculptures. It was simple, elegant, and beautiful.

Preparing the site for a dry shade garden is the first key to success. If trees or shrubs are blocking the sunlight, one option for most trees (except spruce) is to limb them up or thin the branches. I strongly suggest hiring an International Society of Arboriculture (ISA) certified arborist, rather than attempting to do it yourself.

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Adding several inches of organic matter, such as compost, shredded leaves, mushroom compost, and aged manure to the soil, will help to retain moisture. When planting under established trees, try not to cut any of the roots. Top the garden with a four- to 10-cm layer of organic mulch. For the first year, water new plantings at least once a week, or more often if you find the soil is drying out. Choose drought-tolerant plants and in subsequent years supplementary watering should be needed only during long periods of drought.

Woody plants  

Woody plants add height, structure, and winter interest to the garden. Some that will grow in dry shade in Calgary include:

• chokecherry, a small native tree with white flowers in spring and attractive red, astringent fruits that make lovely jelly and syrup. Be aware that it can sucker.

•dwarf European cranberry, a hardy shrub that tolerates dry shade, forms a small, neat mound of dark green maple-like foliage.

•white snowberry is a suckering shrub useful for shrub borders or hedges, or for naturalizing in woodland areas. The white berries will shine in the shady winter garden.

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• ninebark is drought-tolerant once established and many varieties can tolerate part shade, although flowering might be reduced.

Perennials  

There are many perennials to choose from for a dry shade garden and some have beautiful flowers and variegated or bright-coloured foliage to light up those dark corners. Many are vigorous spreaders in optimal growing conditions but are usually more restrained in drier, shadier areas. Most of these are growing in my own garden:

lady’s mantle, goatsbeard, wild ginger, bergenia, Siberian forget-me-not, lily-of-the-valley (but be warned this might be too aggressive, even in dry shade), barrenwort, big root geranium (recommended for even the toughest spots), hosta, yellow archangel, spotted deadnettle (White Nancy is a relatively well-behaved cultivar), false Solomon’s seal, ostrich fern, Solomon’s seal, lungwort and lesser periwinkle.

Native perennials  

Choose these native perennials for dry shade:
Canada anemone, bunchberry, northern bedstraw, veiny meadow rue, early blue velvet viola.

Remember to add a few containers of shade-tolerant annuals such as impatiens, begonia, browallia, lobelia, wishbone flower, and fuchsia; and a sculpture or two. That troublesome dry shade area just might become your favourite part of the garden.

Ann Van de Reep writes on behalf of the Calgary Horticultural Society.

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