This is the last of a series of columns dedicated to the pleasures and surprises found in gardening in the cool of a shady garden. In previous articles, I discussed the types of plants that grow best in filtered shade and dappled shade. This article is devoted to plants that work where the sun almost never shines — dense, deep shade.
Residents of the Potomac River corridor can escape the heat of summer in the shade of the woodland areas that run along the river and its tributaries. The large leafed tree canopy and evergreens in these areas can result in conditions where the understory growth gets very little or no direct sunlight. Urban gardeners can also find this kind of shade in enclosed yards where walls or trees block direct sunlight.
This dense, deep shade can be a serene, lush refuge and there are plants that will enhance that sense of shelter while at the same time providing textural and color interest. Plants such as astilbe, ferns, foam flower, hosta, lamium, solomon’s seal, wild ginger, wintergreen, trilliums, and vanilla leaf (achlys triphylla) all do well in deep shade and are aesthetically suited to creating a woodland bower. Ground covers such as English ivy, and ajuga will also thrive in deep shade; plant them if you garden in an enclosed area where these hardy non-native plants will not spread beyond the garden.
However, the bulk of this column will deal with an especially good plant choice for areas of deep shade — ferns. Ferns are naturally found in woodland areas, and love the organically rich soil found beneath the tree canopy. They can be massed in the garden as a ground cover or used as a focal point. Gardeners with a wooded lot can use ferns to enhance the woodland quality of the garden. Gardeners dealing with an enclosed garden can combine them with the plants mentioned above to achieve textural interest and lighten up shadier areas.
In our area, ferns such as the Japanese shield fern (dryopteris erythrosora) and Christmas fern (Polystichum acrostichoides) can be planted as ground cover; they grow one to two feet in height and spread slowly through rhizomes. Better yet, they are unpalatable to deer and rabbits.
Ostrich fern (Matteuccia struthiopteris) is a standout in the full shade garden. It can grow to six feet in height and spread to eight feet. The tall upright arching fronds resemble ostrich plumes. Ostrich ferns can be combined in an ornamental garden with hosta, astilbe, caladiums and foam flowers.
The Marginal Shield fern (Dryopteris marginalis), native to North American woodlands, is fairly easy to grow and adapts to all kinds of shade. The marginal shield fern is a wonderful ground cover. Its evergreen fronds can grow to eighteen inches in height and spread up to two feet in width.
If you want a fern that has an airy, delicate foliage but is very hardy, the Maidenhair ferns (Adiantum pedatum) are a great option. They are deciduous and therefore will not provide winter interest, but the frilly fronds are stunning when planted in masses, and the coiled young fiddle heads that emerge in spring have a pinkish color.
Although not native to North America, the Japanese painted fern (athyrium niponicum) is a magical addition to the full shade garden, especially the ‘pictum’variety. It is a deciduous fern that will naturalize in our area, forming a dense colony of plants. The fern gets its name from the gray-green fronds overlaid with silvery patterns that look like they have been ‘painted’ on.. This type of fern tolerates the depredations of rabbits and deer do not like them.
Perhaps my favorite of all ferns in the shade garden is the hardy Christmas fern. It retains its deep green color until well after Christmas, hence its common name. Its leaves do not begin to fade and appear ‘browned out’ until just before the new fronds appear in spring. The Christmas fern will grow to two feet in height and width and, in my garden, this fern has tolerated sporadic watering, rocky and clay-compacted soils, and the occasional munching of rabbits and deer.
In the next few weeks of hot summer weather, head for the nearby public woodland gardens to see how lovely ferns can be in the shade. Huntley Meadows Park near Hybla Valley has an excellent woodland walk, and Meadowlark Botanical Gardens, off the Dulles Toll Road near Wolf Trap, has a beautiful fern walk as part of its Potomac Valley Native Plant Collection.
Eleni Silverman is a Master Gardener, Vice President of the Belle Haven Garden Club, Chair of the Landscape Committee at Thomas Jefferson High School for Science and Technology and author of the garden blog "Belle Haven Garden Maven." She admits to a fascination with all things gardening, believes even compost is engaging, and will eagerly discuss the relative merits of leaf mold versus hardwood mulch.