Gum trees (Eucalyptus spp.) are prized for their aromatic foliage, drought tolerance and the shade they create in the yard. But that shade -- along with gums' tendency to soak up most of the moisture and nutrients in the soil and create dense leaf litter on the ground -- also makes choosing appropriate plants for understory planting a challenge. For the best results, choose shade-tolerant plants with shallow roots that thrive in occasionally dry sites.
Annuals add bright color during the growing season. Shallow-rooted choices include petunias (Petunia x hybrida), which grow in a range of colors -- from white and pink to red and purple -- and sizes, from 6 to 14 inches tall. Petunias flower from spring through summer and tolerate drought and partial shade. Verbena (Verbena x hybrida) blooms from late spring through autumn and grows from 6 to 12 inches tall. These drought-tolerant annuals come in blue, white, pink and red tones and grow in sun to partial shade exposures.
Perennials grow for at least four seasons, some for much longer. Varieties for gum tree understory planting include the bergenia (Bergenia cordifolia). This 18-inch-tall perennial blooms in spring with deep pink flowers and has dark, lustrous leaves. It's hardy in U.S. Department of Agriculture plant hardiness zones 3 to 8 and prefers partial shade exposures. At the sunny edge of the gum understory, plant hardy ice plant (Delosperma cooperi). Reaching heights of just 3 to 6 inches, this drought-tolerant perennial has succulent-like foliage and blooms with bright pink and purple flowers in summer. It's hardy in USDA zones 6 to 9 and prefers dry, sandy soil.
The bearberry cotoneaster (Cotoneaster dammeri) grows well under gum trees. This evergreen shrub tolerates drought and partial shade and spreads rapidly to 6 feet wide and 2 feet tall. Its evergreen foliage contrasts with its white spring flowers and red berries. Bearberry cotoneasters are hardy in USDA zones 5 to 7. For a taller shrub, plant a glossy abelia (Abelia x grandiflora). This semi-evergreen grows to 6 feet tall and is named for its shiny, dark foliage that turns red-bronze in winter. Hardy in USDA zones 6 to 9, this shrub tolerates drought and grows in partially shaded sites.
Groundcovers fill in empty spots under your gum tree. Choices include the shore juniper (Juniperus conferta), a fast-growing evergreen that forms a dense mat of foliage. Shore junipers grow in partial shade and dry soil. They're hardy in USDA zones 6 to 8 and reach heights of 10 inches. The "Blue Pacific" cultivar has blue-green foliage and spreads to 10 feet wide. Liriope (Liriope spicata) grows to 12 inches tall with a similar spread. This drought-tolerant groundcover has grass-like, evergreen foliage and grows in clumps. It's hardy in USDA zones 4 to 9 and thrives in partial to full shade.