Made for the Shade: Shade-loving Plants

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.

Our native sword fern, Polystichum munitum, is invaluable for dry shade. The dark-green fronds are leathery, about 90 cm (3 ft.) in length and typically narrow and sword shaped – hence the common name. They stay green all winter, though they tend to break down during cold snaps or snowfall. Come spring, a burst of fresh green growth emerges from the centre of the crown. At this time the older fronds may be trimmed off or left to die back naturally. This fern can survive the dry summers we have recently had and will even thrive under moisture-stealing trees like Douglas fir.

An Asian relative of our maidenhair that is native to the Himalayas, Adiantum venustum, is also excellent for coastal gardens. Its growth habit is very similar to the indoor potted maidenhair fern. It has the typical ebony stems with narrowly triangular fronds up to 30 cm (12 in.) in length that stay a gorgeous fresh green depending on the severity of the winter. I first fell in love with this fern in my friend Joan Paterson’s garden, where she has it planted under the risers of a red brick step entryway that faces east and gets plenty of shade from neighbouring trees. I was so taken with it that, in typical garden fashion, she gave me a small piece, which is now flourishing in a pot on my north-facing balcony. It is said to be hardy to zone 5, but tends not to be evergreen when the temperature dips to -24°C (-10°F).

Another gorgeous native plant that is underused in shady home gardens is our wild ginger. Asarum caudatum is a low-growing evergreen perennial with extensive trailing rhizomes that root freely and form large mats. The heart-shaped, mid-green leaves, 10 cm (4 in.) in length and up to 15 cm (6 in.) wide, are covered with fine hairs. The leaf stalks are up to 20 cm (8 in.) long. In spring the purplish bell-shaped flowers are concealed under the foliage. This plant really needs leafy, composted soil and plenty of moisture to do well. It is native to coastal regions and is only hardy to zone 9. However, those of you in cooler parts of the province can try A. canadense, Canadian wild ginger, which is quite similar in appearance but deciduous. Native to eastern North America, it is hardy to zone 2.

Sarcococca ruscifolia is an amazing, smallish, low-growing shrub that is absolutely a must-have for the shade. Often sold under the common name of sweet box, it is a dense, slow-growing bush that reaches a metre (39 in.) in height and width. Its graceful arching shoots are covered with dark-green glossy leaves that look as if someone has polished them. The stunning foliage alone is enough reason to give it garden space. But in late winter-early spring tiny clusters of creamy white, highly fragrant flowers are borne in the leaf axils, perfuming the air for several metres around. Native to western and central China, it is only hardy to zone 8. Also wonderfully fragrant, Sarcococca hookeriana var. humilis is hardier, to zone 6.

In Kathy Leishman’s garden, this is planted on the north side of her home near an entry door. She has combined it with ferns and hostas, and the different leaf structures make a pleasant green tapestry – to say nothing of the perfume that welcomes winter visitors. It is always such a pleasant surprise, stopping you in your tracks to wonder where it comes from.

Hellebores have long been associated with shade plantings and again they work best in a semi-shaded situation, preferably under deciduous trees and tucked in underneath such shrubs as Hamamelis or Viburnums. They can tolerate dry shade in the summertime, plus if they are happy with the conditions they tend to cross and seed themselves freely, naturalizing in such situations. The only soil conditions they cannot tolerate are poorly drained. A popular group of this family are Helleborus x hybridus, which are of garden origin hybrids of Helleborus orientalis, which come to us from Northern Greece, Northern Turkey and over into the West Caucasus making them hardy to zone 6. The flowers appear early in the year on thick stems on loose cymes of up to four pendant saucer-shaped flowers 5-8 cm (2-3 in.) across ranging in colours from whitish-green to dark maroon. The insides of the blossoms are often intricately spotted.

Last but not least, I must mention a rather common groundcover that is stunning when planted in shade. It is good old creeping jenny, the golden form, Lysimachia nummularia ‘Aurea.’ The A to Z Encyclopedia refers to it as a rampant, prostrate, evergreen perennial – and it is true that if it likes where it is planted it can take over. But there is always the hoe! This mat-forming plant has broadly ovate to rounded, golden leaves up to 2 cm (1 in.) long. The golden colour is further enhanced in shade, bringing light to a dark corner, particularly on a dull day, and making it a perfect companion for shade-friendly ferns and hostas.

David Tarrant of the UBC Botanical Garden is a well-known gardening expert, author, and host of Spring, currently on HGTV.