Dry Shade Strategies
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DRY SHADE By following a few simple guidelines, you can create a diverse and colorful STRATEGIES garden. C. Colston Burrell Every garden has a dry, shady spot where it looks as though nothing will survive. But looks can be deceiving. There is a whole host of interesting and attractive plants that will not only survive in the heavy shade of a tall building or full tree canopy, but actually thrive there, contending with root competition and summer gloom to bring you flowers and decorative foliage all through the year. The first point to recognize is that much dry shade shift in expectations on the gardener’s part, since a OPPOSITE: is not permanently shady, or permanently dry. Of dry shade garden will never be as lush as a creekside Many spring-blooming course most wooded sites become dry in summer, as planting. But you can still create a beautiful and satis- bulbs and perennials the trees block out not only light but also rain. Thirsty fying display. will flourish under the tree roots, moreover, quickly swallow up whatever If you must tinker, the best cure for dry soil is skirts of deciduous trees does get through to ground level, so herbaceous plants organic matter, lots of it. Applying it can be tricky. and shrubs (here a foth- and shrubs must then make do with leftovers. But at Dense roots often make digging impossible, and root ergilla), making their other times of the year neither water nor light may be disturbance may damage or kill a tree. Besides, mature show before the woody in particularly short supply, and this is the key to sur- tree roots often work their way above the ground sur- plants leaf out. The vival for a number of good garden plants. face. Yet you can with care cover them, building up woody plants In a forest, for example, deciduous trees allow con- enough soil depth for planting and increasing the can then carry on the siderable light to stream through bare branches in water-holding capacity. Add light mulch or composted show. spring and autumn. Soil moisture is ample at the manure gradually, layer by layer, giving the trees time beginning and end of the season. Here, early-bloom- to adjust. Never dump heavy soil onto tree roots; ing bulbs and wildflowers excel. As the canopy leafs burying them this way may cause permanent damage. out and competition for limited moisture intensifies, Where roots are not too closely knit, you can work these plants retreat. organic matter further down into the soil. As you dig, Conditions under a wide-spreading lawn tree or in avoid cutting large roots. Small roots severed by the a suburban woodlot are similar to those in a forest, and shovel’s blade will quickly regrow. Some trees, espe- Hardy cycla- so are the plants that like them. More challenging cially early successional species like most maples and men, Cyclamen are plantings under conifers. Their shallow roots and hederifolium, dense canopy ensure that light and water are hard to shows its flowers come by anytime; yet again nature shows you what will first, then the grow there. In pine and hemlock forests, plants with marbled leaves. evergreen leaves are the most common understory ele- ments. Evergreen leaves help a plant cope with a dif- ficult site in two ways: first, they allow it to produce food whenever temperatures are above 45 degrees F, and second, their leathery texture substantially reduces water loss. So for a garden spot with year-round shade, evergreen plants are the wisest choice. Dealing with Dry Soil Shaded spots are dry either because not enough mois- ture reaches the soil or because the soil won’t hold it. Or both. There are various strategies for dealing with dry soil, but the simplest is to ignore it and choose plants adapted to drought. This process may involve a ILLUSTRATIONS BY SHERRY MITCHELL 17 7 (5x) 11 12 2 (2x) 5 5 10 8 8 9 5 8 3 9 6 (2x) 1 (2x) 4 (2x) COMBINATIONS FOR YEAR-ROUND BEAUTY A hypothetical planting plan created by the author blends bulbs, perennials, and shrubs to provide four-season variety of shapes, textures, and colors—from both flowers and foliage (Plants shown in profile at right). 1. Callaway wild ginger 8. Long-eared holly fern Polystichum neolobatum Asarum shuttleworthii ‘Callaway’ Interplanted with 12 Leucojum vernum 2. White wood aster Aster divaricatus 9. White-edged variegated sacred lily Interplanted with 12 Narcissus ‘February Gold’ Rohdea japonica 3. Evergold Sedge Carex oshimensis ‘Evergold’ Interplanted with 24 Galanthus spp. 4. Frohnleiten barrenwort 10 . Saruma Saruma henryi Interplanted with 12 Anemone ranunculoides Epimedium ×perralchicum ‘Frohnleiten’ 11 . Zig-zag goldenrod Solidago flexicaulis 5. Lenten Rose Helleborus ×hybridus Interplanted with 12 ‘Formosa’ Interplanted with 12 Anemone nemorosa ‘Vestal’ Tulipa 6. White variegated monkey grass 12 . Maple-leaf viburnum Viburnum acerifolium Interplanted with 25 ‘W. P. Milner’ Ophiopogon japonicus ‘Fuiri Gyoku Ryu’ Narcissus 7. Variegated solomon’s seal Polygonatum odoratum ‘Variegatum’ black gums, take root disturbance in stride. I have Design Ideas for Shady Sites had good luck digging under my tulip poplars and A well-designed shade garden uses all the elements of a hickories. But be very cautious around oaks, beeches, natural ecology—trees, shrubs, perennials, and bulbs. and sugar maples. Incidentally, there is a danger in The shrub layer is usually the most underutilized com- making your soil too rich and welcoming: tree roots ponent, which is a pity because it serves an important may take over the space before your new plantings get design function. Shrubs create architectural frames or a chance. The trick is to get your plants to establish “bones,” that give structure to the garden and help link their roots first. The larger the soil pocket, the easier the trees and perennials visually. Like interior walls, this is to do. they can divide and define outdoor spaces. Shrubs pro- 18 PLANTING PLAN BY C. COLSTON BURRELL the gardener vide dramatic foliage, colorful flowers, decorative few deciduous shrubs that excel in summer without fruits, and provocative winter silhouettes. They also supplemental water are maple-leaf viburnum (Vibur- supply backdrops for the herbaceous plantings that num acerifolium, Zones 4–8), bush honeysuckle (Diervilla keep the garden colorful during the growing season. spp., Zones 3–8), wild hydrangea (Hydrangea arborescens, With judicious selection, you can have shrubs in Zones 4–8), and witch hazel. In dense shade, ever- bloom from the earliest spicebush (Lindera benzoin, greens outperform most deciduous shrubs. Estab USDA Zones 5–8) in late winter to the last witch lished mountain laurels are nearly indestructible. hazel (Hamamelis virginiana, Zones 4–8) in November. Alexandrian laurel (Danae racemosa, Zones 7–9), with Fruit is another feature—most native shrubs have arching stems of fine-textured, leathery leaves, and White attractive berries that bring color to the autumn and Florida leucothoe (Agarista populifolia, Zones 7–9) are wood aster, winter garden, and delight mockingbirds, robins, and exceptional shrubs that deserve wider recognition. For Aster divaricatus, waxwings. And for winter interest there are shrubs groundcover effect, try sweet box (Sarcococca hookeriana a native of dry wood- whose bare branches look beautiful covered with var. humilis, Zones 5–8), starting with small plants that lands with clusters of snow. These include the erratic forms of chokeberry are easily inserted between tree roots. late- (Aronia arbutifolia, Zones 4–8), oak-leaf hydrangea I am fascinated by woodland perennials; some are season flowers. (Hydrangea quercifolia, Zones 5–8) and witch alder enchantingly beautiful, while others are more curi- (Fothergilla gardenii, Zones 6–8). For a profile of ous than handsome. Native woodland plants are Fothergilla, see page 14. keyed to the same seasonal rhythm. They As you plan your plantings, keep in mind that bloom when moisture is abundant, then quiet- shrubs and small trees are natural trellises for vines. ly disappear as the soil dries out. This Grow a clematis up through a viburnum and double ability to go dormant in summer makes the impact. Try yellow passion vine (Passiflora lutea, plants such as bloodroot (Sanguinaria Zones 6–8) or Carolina jessamine (Gelsemium semper- canadensis, Zones 3–9), trout lily virens, Zones 7–9) to decorate the stems of dogwood or (Erythronium spp.), trillium, Virginia blue- fringetree (Chionanthus virginicus, Zones 4–8). bells (Mertensia virginica, Zones 3–8), and Dutchman’s breeches (Dicentra Tough Plants with Good Looks cucullaria, Zones 4–8) perfect for dry Your choice of shrubs for dry shade is somewhat limit- spots under deciduous trees. ed, especially where root competition is severe. Still, a The end of a long, dry summer is October/November 2002 19 12 PERENNIALS FOR DRY SHADE Epimediums, also known as barrenworts, bishop’s Wild ginger Coral bells hats, or fairywings, are perfect candidates for dry, Asarum spp. Heuchera americana shaded spots. All species exhibit good drought toler- Cast-iron plant Welsh poppy ance, but it is the evergreen species such as E. pinnatum Aspidistra elatior Meconopsis cambrica and its popular hybrid E. ×perralchicum ‘Frohnleiten’ Hardy begonia Prairie phlox (Zones 4–8) that really perform in dense shade and Begonia grandis Phlox pilosa tolerate root competition with aplomb. Another Bergenia Zig-zag goldenrod tough hybrid is E. ×versicolor, which has several out- Bergenia cordifolia Solidago flexicaulis standing selections. ‘Cupreum’ and ‘Versicolor’ are pale Siberian forget-me-not Goldsmith comfrey apricot to copper-colored, while ‘Sulphureum’ and Brunnera macrophylla Symphytum grandiflorum ‘Neosulphureum’ sport soft yellow flowers. The excit- Robb’s wood spurge ‘Goldsmith’ ing new introduction ‘Cheery Tars’ has bicolored pink Euphorbia amygdaloides Inside-out flower flowers. I have a mixed planting of epimedium under ‘Robbiae’ Vancouveria hexandra mature hickories in pure clay that seldom gets watered.