The sprawling limbs of that grand old oak are wonderful for shielding the house from summer heat, but not so wonderful for creating a space to grow perennial flowers and shrubs.
Or so many a homeowner may think.
After all, the soil under a large tree canopy is bone dry because:
- The dense mass of leaves limits the amount of rainfall that reaches the ground.
- The thirsty and extensive system of feeder roots soaks up all available water — as much as 50 gallons a day, according to some sources.
There's a term for this gardener's lament: it's called dry shade.
"Dry shade is common in many parts of the country where large, mature, over-story trees are prevalent in and around yards," said Amanda Campbell, manager of display gardens at the Atlanta Botanical Garden. "Low, shady, wet conditions aren't as common — particularly in the urban environment. Yards and landscapes are disturbed environments that have been graded and flattened out so that the conditions for lower, wetter places have been taken away."
Dry shade can also refer to areas under eaves, covered porches or balconies or on the lee (sheltered-from-the-wind) side of houses, says Kacey Cloues of intown Atlanta nursery GardenHood.
Challenges of dry shade
Perpetually dry soil under large trees poses more challenges for gardeners and ornamental plants than just constant competition for water and nutrients.
"In residential yards, the areas under big trees tend to be spaces where people congregate," said Cloues. "Kids have swings in the branches and adults set up picnic tables or lounge chairs in the comfort of the shade. "In short," she says, "there tends to be activity beneath big trees that also works to compact the soil, making it more difficult for new plants to get established there."
On top of that, while the pallet for shade plants is as extensive as that for sun plants, gardeners will need to pay more attention to that pallet to find a variety of colors and textures when buying plants for shade, said Campbell.
Trees also provide a habitat for squirrels, chipmunks, rabbits and deer. "Sometimes deterring these foraging animals can be a challenge," she added.
Choosing plants for dry shade
Believe it or not, Campbell and Cloues say, there are a large number of plants for gardeners to choose from that will do well in dry shade. Some of the considerations in choosing these plants, other than occasionally supplying water and nutrients, are to pick evergreen ones that can tolerate winter sun after the leaves drop and be aware that plants that have super delicate leaves could be damaged by leaf blowers in the fall. With these considerations in mind, here are a few plants they suggest will do well in the dry shade garden:
- Rhodea (sacred nippon lily) — A clumping, evergreen perennial.
- Sarcococca (sweetbox) — A shrubby evergreen with amazingly fragrant flowers in winter. (Some species grow more like shrubs, others more like low groundcovers.) Deer- and rabbit-resistant.
- Sedum tetractinum (woodland stonecrop) — A very low-growing, creeping sedum that also works well in containers or hanging baskets that tend to stay dry and shady
- Dryopteris erythrosora (autumn fern) — An evergreen perennial fern.
- Cyrtomium falcatum (Japanese holly fern) — Another evergreen perennial fern. Deer- and rabbit-resistant.
- Helleborus (lenten rose) — A clump-forming, evergreen that blooms in winter (seen at right). Deer- and rabbit-resistant.
- Aspidistra (cast iron plant) — A clumping evergreen nicknamed the "cast iron plant" because it can survive almost anywhere (even indoors) with minimal care. Very slow-growing, but a well-established stand is worth the wait! Available in a wide variety of forms: tall, short, striped and speckled, to name a few.
- Carex ('Sparkler', 'Evergold', 'Blue Bunny') — These three are evergreen, clump-forming grasses that can handle dry shade and dappled sun throughout the day. Great for tucking into nooks and crannies in shady rock gardens, along pathways, in and among large, exposed tree roots, or in containers or hanging baskets. They provide great textural contrast to broader-leafed perennials.
- Beschorneria septentrionalis (false agave) — This agave relative is perfect for the gardener looking for the truly unusual! It grows about a foot and a half tall by three feet wide, is evergreen and spineless and thrives in dry areas that get part sun/part shade. Once it's established and happy, it will send up a five-foot tall flower spike in late fall/early winter.
- Also — Taxus, Cephalotaxus, some Cryptomeria, Chelone (deer resistant), Hostas, Thelypteris, Acanthus (all deer resistant), Iris tectorum, Astilbe, Chrysogonum (deer resistant), Neviusia, Asarum, Heucherra and Epimedium
- Cephalotaxus (yew) — These come in varieties that stay low and creeping, some that grow into medium sized shrubs and others that grow tall and narrow (like sky pencil hollies). They are evergreen, and the tall forms are great for screening. Deer-resistant.
- Hydrangea quercifolia (oakleaf hydrangea, pictured at top) — Hands down, one of the best shrubs for hot, dry shade climates. It features gorgeous flowers in late spring and amazing rust-to-plum-colored fall foliage. This deciduous plant can also handle quite a bit of direct sun, so they're perfect for those woodland spots that tend to get sun at different times during the day through breaks in the canopy.
- Hydrangeas arborescens — A bit less finicky than H. grandiflora and H. serrata.
- Thujopsis - another great conifer for dry shade. Forms vary from mid-sized pyramidal shrubs to low, mounded shrubs that have the texture of coral. Deer-resistant.
- Ruscus (butcher's broom) — An evergreen with great texture for the shade garden. Tolerates really dry soil. Deer- and rabbit-resistant.
- Osmanthus heterophyllus 'Goshiki' and 'Sasaba' (false holly) — Evergreen spiny leaves make a protective screening hedge. 'Goshiki' has multi-hued variegation that really stands out in a shady spot. 'Sasaba' has finely dissected elegant foliage that is sharp to the touch. Best used as a specimen. Deer won't touch either of these!
- Also: Podocarpus (partial shade), some Ilex and Camellias
Bulbs for dry shade
Some bulbs will also adapt will to dry shade. Becky Heath of Brent and Becky's bulbs in Gloucester, Virginia, says her experience is that the following perform fabulously in this condition:
- Cyclamen, Arum, Oxalis, Scilla and Polygonatum.
- Others to consider — Anemone hybrida, Anemone blanda, Narcissus and Dicentra
How to grow plants and bulbs in dry shade
Even though the plants listed above as well as others can adapt to dry shade, they will still need water, especially when the look stressed during the heat of summer.
"When planting in dry shade, the most important thing a gardener can do to help ensure new plants survive is dig a hole twice the size of the new plant's root ball," Cloues said. It's also important, she added, to mix a lot of rich compost in with the existing soil when back-filling the planting hole and to water the new plantings deeply three times a week for six months. This will help them become established before leaving them to contend with the harsh conditions of dry shade.
If there are too many roots in the way to dig a proper hole, either try a different spot or pot the plant in a decorative pot instead of putting it in the ground, Cloues advised.
Once planted, to help conserve water add mulch to the natural mulch the tree will supply when it drops its leaves in the fall, urged Campbell. In addition to conserving water, mulch and decaying leaf litter will enrich the soil with nutrients as they break down. Campbell also advises top dressing with compost once a year as another way to loosen the structure of the soil to make it less compacted and to add nutrients, which she says can be hard to get in dry shade.
Growing bulbs in dry shade
Almost all bulbs need some sort of moisture after planting to encourage root development, Heath said. Planting in the fall or early spring, when rains are often present helps encourage good root growth, she said. When Mother Nature doesn't cooperate, she says to just drag a hose over to the bulbs and give them enough water to get the roots going.
But, be careful, she advises. Once established, it's important not to overwater these bulbs. "In this case, you literally can kill them with kindness!" she said.
Depending on how much leaf mold has naturally enriched the soil, Heath also likes to give bulbs a boost by adding good, rich compost.
Something to be aware of, she warned, is that some trees are shallow rooted. These can become very unhappy if their roots are cut into or are covered too deeply with additional soil or compost.
Following these guidelines can turn a barren ground eyesore into a new garden area that blends color and texture into a centerpiece of attention.