Coniferous, or evergreen, trees add value to the landscape by increasing property values, lowering summer air conditioning costs and decreasing winter heating bills. However, coniferous trees have thick, dense canopies that don't allow much sunlight or moisture to reach the ground. This limits gardeners' choices of plants to grow underneath these trees. For the best results, choose plants that tolerate both shade and dry soil. Plants must also be small so as not to grow into low-hanging tree branches.
Most perennials prefer sunny sites with well-drained soil, but a few, drought-tolerant varieties can grow or even thrive in shade. These include bugle weed, a low-growing perennial that blooms with purple, blue and white blossoms in early to late spring. This tiny flower only grows between 15 to 22.5 cm (6 and 9 inches) high, but spreads quickly to cover bare spots. Bugleweed prefers partial to full shade and well-drained soil.
Wild ginger also prefers shady spots. Another small perennial, wild ginger grows from 15 to 25 cm (6 to 10 inches) tall and has purple spring flowers and attractive, heart-shaped foliage. Both of these species grow in the UK. Other good choices include bergenia, cast iron plant, primrose and stonecrop.
Shade-loving, drought-tolerant ground covers offer a low-maintenance option for under-tree sites. The clumping and creeping liriopes both thrive in shade and dry soil. These evergreen plants grow up to 45 cm (18 inches tall) with similar spreads and have attractive, variegated foliage. Clumping liriope produces showy, white to purple spikes of flowers in late summer, while creeping liriope blooms with more subtle lilac-coloured blossoms. Creeping liriope is hardy in and clumping in the UK.
Creeping mahonia, another evergreen, tolerates shade and a range of soils. This spreading plant grows to 25 cm (10 inches) tall but spreads up to 1.5 m (5 feet) wide. Hardy in the UK, creeping mahonia blooms in late spring with small, yellow blossoms followed by black berries. Other options include English ivy, Carolina jessamine, Corsican violet, periwinkle and sweet woodruff.
Like coniferous trees, evergreen shrubs keep their foliage year-round. Choose small species to avoid root competition. Several boxwood varieties thrive in dry sites, including the English, Japanese and littleleaf cultivars. All prefer partial shade and well-drained soils. The slow-growing English boxwood has deep, lustrous foliage, grows to 90 cm (3 feet) tall and is hardy in the UK. The Japanese boxwood has glossy, oval foliage and grows from 3 to 6 feet tall. Littleleaf boxwood grows from 90 cm to 1.2 m (3 to 4 feet) tall, has light-green, dense foliage and produces fragrant spring flowers. The Japanese and littleleaf shrubs are hardy in the UK. Other small evergreens include butcher's broom, Oregon grape holly and yeddo hawthorn.
Deciduous shrubs that tolerate dry shade include the blue spiraea, a 90 cm (3 foot) tall shrub that produces butterfly-attracting blue flowers in late summer. Blue spiraea has fragrant foliage and is hardy in the UK.
The black choke cherry blooms with clusters of white spring flowers, followed by black berries. A slow-growing shrub, the black choke cherry grows from 90 cm to 1.5 m (3 to 5 feet) tall and is hardy in the UK. Other small deciduous shrubs include Bulmade spiraea, black jetbead, fragrant sumac and yellowroot.
- Arbor Day Foundation: The value of trees to a community
- North Carolina State University Cooperative Extension; Drought tolerant shrubs
- University of Delaware Cooperative Extension; Drought-Resistant Perennials ... in Zone 7; Jay Windsor; September 1997
- Colorado State University Extension: Drought tolerant groundcovers for shade
- North Carolina State University Cooperative Extension: Perennials