Many gardeners are baffled by problems caused by shade. However, there are numerous plants which prosper in areas where shade occurs, and from these a selection can be made to suit most situations.
Shade exists in many degrees but to evaluate the variations according to any set rule is almost impossible. Some analysis is, however, advisable to determine the types and degrees of shade in the garden at different times of day and during the changing seasons. Such stocktaking should, if possible, be done before selecting the kinds of plants to be grown.
Perpetual shade may be caused by closely planted or dense evergreens, by high walls or buildings located to the south. A lighter and more cheerful shade may exist where light is reflected from a white wall or where distant objects only block the sun. Heavy shade may sometimes be reduced by the judicious pruning of offending trees, but amputation of branches requires skill and restraint. Tall shrubs may be pruned to admit more light and at the same time add to the well-being of the trees.
Shade May Be Seasonal.
A bright spring garden, gay with flowering bulbs, may be very shaded later when leaf-losing (deciduous) trees are in full leaf. Some trees cast a heavy shadow in summer. Here belong Ash and Beech trees, as well as the Norway Maple, under which practically nothing will grow once the trees are old and big. Trees such as Pin Oak, Black Locust and Sycamore create less shade, and so do trees that branch high. Kinds such as Honey Locust and Birch give a pleasant, dappled sunlight and shadow effect. When planting against a building facing north, it is well to remember that although the area may receive early and late afternoon sun, this is much less powerful than the sun at midday.
It is true that most plants prefer a sunny situation, yet some, including Rhododendron maximum, (Rosebay), Leucothoe, Viburnum acerifolium (Dockmackie), and most Ferns actually prefer a shaded location. Shade-preferring ground covers include Ajuga, Periwinkle and Pachysandra. Many herbaceous perennials flourish in deep woodlands but languish in the sunshine, and a large number of these are adaptable for cultivating in shady beds and borders as well as in wild gardens and less formal areas. When appropriate plants that will fit into cultivated and landscaped grounds are considered, many well-behaved natives should be included.
In shaded areas in the wild, there exists every kind of soil condition. There are plants which flourish in shaded bogs, in shaded soils of extreme acidity, in dry, shaded areas, on fiber-matted woodland floors, and in good, loamy soil. In home gardens, conditions are usually more uniform. Yet many cultivated plants set in shade die, not from lack of sun, but from unsuitable soil conditions.
Unless otherwise stated, the plants recommended here all require good, friable (crumbly) garden soil prepared to a depth of 1-2 ft. by spading and by adding generous quantities of compost or other organic matter and some fertilizer. Where the soil is naturally acid, it is prudent to consider planting acid-soil plants only, rather than to recondition the soil, although this may be done by liming. Acid soil exists naturally where Hemlocks, many Pines and other coniferous (cone-bearing) evergreens grow. An acid condition is also usually found under most kinds of Oak trees. If in doubt as to whether a soil is acid or alkaline, the gardener should have a sample soil test made by a State Agricultural Experiment Station or by a qualified person.
If the soil is not acid enough, increased acidity can be built up by incorporating with it leaves and leaf mold or acid peat moss. Peat moss and leaf mold help to condition the soil; sharp (coarse) sand may be used to lighten it if it is of a clayey nature. To conserve moisture and keep the roots cool (shade-loving plants need a moist, cool soil) a mulch should be laid over the soil in shaded parts of the garden. This also prevents packing of the soil by water dripping from trees and shrubs.
It is generally best to avoid setting plants too close to surface-rooting trees, such as Maples. Few plants can successfully compete with such trees for the moisture and nutrients they must have.
On the credit side of gardening in the shade is the fact that the plants usually require less watering, because the sun does not dry out the soil rapidly. Flowers in shaded or partly shaded areas tend to hold their color and freshness longer than do flowers grown in the sun, even though their blooms may be less numerous.
Flowers most attractive in the shade are those with warm colors such as yellow-pink (salmon or apricot), orange and yellow. White is also effective. The colder colors seem to recede; however, blues and purples can be used with good effect in the shaded landscape.
Flowering Shrubs for Full Shade.
Rosebay, Rhododendron maximum, when planted in shade, tends to become lanky. It may be used effectively by planting it with the following deciduous Azaleas (botanically also called Rhododendrons): R. arborescens, Pinxter-Flower (R. nudiflorum), R. roseum, R. Vaseyi, and White Swamp Honeysuckle (R. viscosum). Drooping Leucothoë (L. Catesbaei), which, like the Rose-bay, is evergreen, may also be planted with the above. These shrubs produce white or pink flowers in succession from April through July. Along with these the Hemlocks and Canadian Yew (Taxus canadensis), the only needle-leaved evergreens which will grow in all degrees of shade, may be planted with good effect.
Evergreen Shrubs for Light to Medium Shade.
The Rosebay, Rhododendron maximum, and the Leucothoë mentioned above are useful where shade is light to medium, and for planting in the same soil conditions. Other kinds, suitable for mild climates, include Aucuba and Laurel, Laurus nobilis. The following broad-leaved evergreens, which are not content in deeper shade, may be used: Pieris japonica, with white flowers; Mountain Laurel, Kalmia latifolia, with pink or whitish flowers, which bloom in May or June.
Rhododendron (Azalea) obtusum amoenum has red-purple blossoms, and Rhododendron (Azalea) obtusum Hinodegiri has bright rose-red flowers in April and May. The large-flowered Rhododendron (Azalea) mucronatum also does well where shade is not too dense, but its foliage is less glossy than that of the other two Azaleas here mentioned. Camellias, in climates where they can be grown outdoors, are most handsome shrubs or small trees for growing in partial shade.
For the same kind of location there are a number of handsome evergreen shrubs that have insignificant flowers and are grown for their foliage. Yews fit admirably into this picture. Where no great height is wanted, the shrubby Yews with their short, crowded leaves are recommended. These include the dwarf English Yew, Taxus baccata adpressa, and the dwarf Japanese Yew, Taxus cuspidata nana. Several broad-leaved evergreens are excellent for locations where shade is not too heavy—among them, Japanese Holly, Ilex crenata, both the tall and the dwarf kinds, and the looser-branching Inkberry, Ilex glabra. Euonymus Fortunei and its varieties are useful, especially when allowed to climb.
Deciduous (Leaf-losing) Shrubs for Full Shade.
In addition to the shrubs mentioned above under Flowering Shrubs for Full Shade, the following, which do not have showy blooms, succeed well in comparatively deep shade: Privet, Ligustrum; Acanthopanax Sieboldianus; Snow-berry, Symphoricarpos albus; Japanese Barberry, Berberis Thunbergii; Shrub Yellow Root, Xanthorhiza simplicissima.
Leaf-losing Shrubs for Light Shade.
Among spring-flowering shrubs and small trees that thrive in good garden soil and stand some shade are Cornelian Cherry, Cornus Mas; Spicebush, Lindera benzoin; Kerria, and Weigela. All have yellow blooms except Weigela, which has pink flowers. Many shrubby Dogwoods are eligible for use in light shade, as also are most Viburnums, though not Viburnum Carlesii or Viburnum Burkwoodii, because they require more sun. Enkianthus, which requires an acid soil, is excellent and has handsomely colored autumn foliage. Several species of Bush Honeysuckle are recommended, including, especially, Lonicera canadensis, L. Morrowii and L. tatarica.
Kinds that bloom in summer are Sweet Pepper Bush, Clethra alnifolia; Hypericum frondosum; Hypericum densiflorum; and Flowering Raspberry, Rubus odoratus. The latter, on account of its coarse foliage, is best placed where it will be seen at a distance, perhaps along the fringe of woodland, from where its rose-purple blossoms show effectively.
Vines for Shade.
Among the most satisfactory vines for shade are the following: English Ivy, Hedera Helix; Virginia Creeper, Parthenocissus quinquefolia; Boston Ivy, Parthenocissus tricuspidata; Euonymus Fortunei; Bittersweet, Celastrus; Silver-Lace Vine, Polygonum Aubertii; Akebia quinata; Dutchman’s-pipe, Aristolochia durior; and Climbing Hydrangea, Hydrangea petiolaris.
Ground Covers for Shade.
The following are a recommended list of ground covers suitable for planting in shaded locations: Lily of the Valley, Convallaria majalis; European Wild Ginger, Asarum europaeum; Epimedium; Dwarf Lily Turf, Ophiopogon japonicus; Big Blue Lily Turf, Liriope Muscari; Common Periwinkle, Vinca minor; Japanese Spurge, Pachysandra terminalis; and English Ivy, Hedera Helix.
Perennials, Including Bulbs, for Shade.
There are a vast number of woodland plants that are well adapted for growing in woodland gardens, wild gardens and rock gardens, and a more limited but still generous number that are adaptable for cultivating in perennial borders that are shaded. When preparing a perennial bed or border in a shaded area, select a location where the shade is not really heavy. Perhaps a spot can be found that gets sunshine filtering through the leaves of trees or even a few hours of direct sunlight; or possibly the shadow is from distant trees or buildings or from trees which branch high so that good light from the sides is received. An airy, fairly light condition is desirable for best results. It is simply impossible to grow many plants suitable for a perennial border where shade is really dense or air circulation is not reasonably good.
One of the first requirements in establishing a border or bed of perennials in a partially shaded place is to make sure that the preparation of the soil is very thoroughly carried out before any planting is attempted. This involves spading it to a depth of 8-12 in. and mixing in liberal amounts of organic matter and fertilizer. For plants in shade it is well to have the soil even more fertile than for plants growing in more sunny locations.
The plants that may be grown include:
For Spring Bloom:Bleeding Heart, Dicentra spectabilis; Dicentra eximia; Christmas Rose, Helleborus niger; False Solomon’s-Seal, Polygonatum; Trillium; Bloodroot, Sanguinaria canadensis; Lily of the Valley, Convallaria majalis; Crested Iris, Iris cristata; Blue Phlox, Phlox divaricata (needs spring sun); Epimedium; Virginia Bluebells, Mertensia virginica; Violets, Violas; Daffodils, Narcissi; Winter Aconite, Eranthis; Camassia; Snowdrops, Galanthus; Snowflakes, Leucojum aestivum; Grape Hyacinth, Muscari; Glory-of-the-Snow, Chionodoxa; Spanish Bluebell, Scilla hispanica; English Bluebell, Scilla nonscripta; Polyanthus Primrose, Primula polyantha; English Primrose, Primula vulgaris.
For Summer Bloom:Astilbe (needs moisture); Foxglove, Digitalis purpurea; Aquilegia canadensis; Plantain Lily, Hosta; Day Lily, Hemerocallis; Campanula latifolia; Campanula lactiflora; Rocket, Hesperus; Tiger Lily, Lilium Tigrinum; False Dragonhead, Physostegia virginiana; Coral-Bells, Heuchera sanguinea; Balloonflower, Platycodon grandiflorum; Japanese Primrose, Primula japonica (needs a moist or wet soil); Black Snakeroot, Cimicifuga racemosa; Meadow Rue, Thalictrum.
For Autumn Bloom:Day Lily, Hemerocallis; Plantain Lily, Hosta; Cimicifuga simplex; Mist-flower, Eupatorium coelestinum; Monkshood, Aconitum.
Ferns for Foliage Effects:Maidenhair Spleen-wort, Asplenium Trichomanes; Cinnamon Fern, Osmunda cinnamomea; Interrupted Fern, Osmunda Claytoniana; Christmas Fern, Polystichum acrostichoides; Maidenhair Fern, Adiantum pedatum; Hay-scented Fern, Dennstaedtia punctilobula.
Annuals and Summer Bedding Plants.
Not very many annuals and summer bedding plants succeed in shade, and none will endure really dense shade. Among those that thrive in light or partial shade are the following: Balsam, Impatiens; Wax Begonia, Begonia semperflorens; Fancy-leaved Caladiums; Fuchsia, Nicotiana, Lobelia, and Torenia.