Made for the Shade: Shade Plants

By David Tarrant | Image: iStockphoto

I always say that if you have just moved to a new home it is best to live there through all four seasons before seriously planting or renovating the garden. During that first year you will be able to observe where the sunny, dry spots are, where water or snow lingers longest and which areas get the most shade. Of all these, it’s the shady places that first-time gardeners most often view with dismay, but it is exactly those areas that provide respite from summer heat and allow us to grow a wide array of calming plants.

If you have an established garden with ornamental shade trees, there are many beautiful shrubs and perennials that will enhance those shady areas. But gardening under large groupings of evergreen forest trees, such as coastal Douglas firs and western red cedars or the interior’s lodgepole pines and spruce, is almost impossible and most certainly limited to a very few plants. Not only do these trees create deep shade, they take moisture from the soil, leaving the surface too dry for most shade-loving plants.

Having said that, one solution in such dense shade is to place a few large containers under the trees and fill them with plants like ferns and hostas. It can be difficult to make such plantings look natural, but choosing containers of varied height and grouping them can be quite effective. If the evergreen trees are solitary and have open areas all around them so that some light gets through, then you certainly can try establishing some native semi-shade loving plants.

In nature, sword fern (Polystichum munitum), salal (Gaultheria shallon), dwarf Oregon grape (Mahonia nervosa) and huckleberry (Vaccinium parvifolium) are often found growing happily in such conditions. However one must remember those plants established themselves under trees much younger and smaller. Trying to establish these plants beneath a mature tree is pretty nigh impossible because the conifers have such dense surface roots. Even if one manages to dig a planting hole, add some soil and plant something, the surface roots of the tree will soon find the new soil and choke out the addition. Naturally, one also needs to be careful when working around established evergreens, as covering the surface roots with layers of soil will lead to the death of the tree.

Going back to the solitary trees where more light gets through, try establishing other native groundcovers such as redwood sorrel (Oxalis oregana), rhizomatous and ground hugging with foliage resembling Irish shamrocks. It is found naturally in the redwoods of California all the way up to the Queen Charlotte Islands. Spreading a shallow layer of leafy compost no more than 5 cm (2 in.) deep in spring will encourage redwood sorrel to spread.

The old-fashioned well-loved garden favourite lily of the valley (Convallaria majalis), which comes to us from northern temperate regions and has been around for so long its true origin is unknown, enjoys the same growing conditions as redwood sorrel. The easily recognized pairs of ovate, lance-shaped leaves bear the arching racemes of bell-shaped highly scented blossoms linked so much with weddings and traditional nosegays.

Many people associate camellias and rhododendrons with shade but neither of these bloom in total shade as they require about three hours sunlight each day. I think this misconception stems from the fact they are native to forests in Asia – in fact these forests are not evergreen but deciduous, allowing filtered sun through even in summer. In Japan Camellia japonica occurs naturally on the edges of forests, as do our native flowering current Ribes sanguineum, and the lovely vine maple Acer circinatum, which forms a delightful small tree.

However, if I was tempted to have just one camellia in a semi-shaded spot it would have to be Camellia x williamsii ‘Donation,’ a compact evergreen with glossy bright-green leaves and flowers that are stunning, large and semi-double pink in a sunnier spot and deeper rose-pink and longer-lasting in partial shade.

Shade cast from a building or tall fence is easier to cope with. Even those city lots with narrow spaces between dwellings, allowing only for a concrete sidewalk and some rocks or other fill, can be transformed. The first step is to take up the concrete. Then improve the quality of the soil by adding plenty of compost to make it more like a deciduous forest soil. Lay some flagstones for a path, and fill in the rest of the space with shade-loving plants.

Here are some of my favourite plants for the shade:
Ferns are invaluable for shade and my all-time favourite is our native maidenhair fern, Adiantum pedatum. This deciduous to semi-evergreen fern (depending on the severity of the winter) is recognizable by its shiny ebony stems. The broadly palmate fronds of triangular segments stay a fresh, spring-like green all summer long. Underground rhizomes support this delightful plant. Its close relative, Adiantum pedatum subsp. aleuticum, is very similar. Both have a wide range in North America and are, surprisingly, hardy to zone 3.

One of the best North American native ferns – so hardy (to zone 3) yet underused – is the ostrich fern (Matteuccia struthiopteris). It has giant shuttlecocks of broad lance-shaped, pale-green pinnate fronds up to 1.2 m (4 ft.) in height. Later in the season it produces fertile fronds in the centre, adding further intrigue and interest. I have seen a magnificent planting of these under pines in the grounds of Olds Community College in Alberta, which really proves its hardiness.