As we head into the heat of summer, many gardeners in the Washington area ask for recommendations of small trees or shrubs that can add interest to their landscapes. Fortunately, there are many ornamental summer-flowering shrubs and small trees that do well in our climate. Here are some examples that will create interest from now until the first frost:
• Glossy abelia (Abelia X grandiflora) is a deer-resistant broadleaf evergreen shrub with white flowers tinged pink that drenches the air with fragrance most of the summer. In fall and winter, its foliage turns a maroon color. There are many hybrids, including “Golden Glow,” which offers golden foliage with yellow-edged leaves; “Cloud 99,” with panicles of white flowers, and “Lavender Mist,” with fragrant lavender flowers and gray-green foliage providing a heavy flush of bloom from June to August. It has a compact growth habit, and the semi-evergreen leaves of Lavender Mist change to burgundy purple in fall and dark purple by mid-winter.
• Bigleaf hydrangea (H. macrophylla) is a group of plants that definitively declare summertime. When I think about the large, round blue and pink flowers on these shrubs, it brings back childhood memories of summer. The heat and humidity are what I remember most, because these plants are showiest in July and August. They are shade-tolerant, and deer tend to leave them alone. Big, blue globe flowers usually indicate that plants have availability of aluminum and an acid soil; purple-to-pink flowers are a sign that the soil is more alkaline and closer to a neutral pH of 6.5 to 7.
• Crape myrtles can grow into shrubs or small or large trees, depending on the cultivar and how they are pruned. The plant pushes growth from almost any point where it is cut, including places where large branches have snapped or suffered cracks in the stem. Ours is growing new stems directly out of the wood from areas damaged last winter. When grown in full sun and moist, well-drained soil, all forms of crape myrtles will flower throughout summer. Pocomoke (Lagerstroemia indica X fauriei “Pocomoke”) is a dwarf crape myrtle that grows three or four feet tall. A larger tree form hardy to this region is “Natchez,” with brilliant white flowers all summer. It’s a fast grower, reaching about 20 feet high and wide within 14 years. The trunk of Natchez is smooth, and when the bark sloughs off the trunk and branches, it exposes a cinnamon-brown, sinewy trunk that is striking year-round. The white flowers against the contrasting bark are beautiful. There are many crape myrtle hybrids hardy to this region, which makes them a good choice for a flowering shrub or tree in summer. But don’t plant them where they will shed their flowers on cars or on walkways, where they will be tracked into your house.
• Goshiki osmanthus (Osmanthus heterophyllus “Goshiki”) is a deer-resistant, shade-tolerant hybrid with a handsome cream and light-green marbled variegation on its thorny, broadleaf evergreen foliage. This makes it an outstanding complement to green shrubbery. I haven’t seen deer browsing the leaves of this Asian-native hybrid. It retains its cream-colored marbled foliage through winter.
• Oakleaf hydrangea is a handsome summer shrub with a peeling bark. It loves organic material and performs well along the edge of the woods. The leaves take on an oak leaf appearance as the flowers begin to open in June. This hydrangea has a white cone-shaped flower that holds for about four weeks beginning in June. The display continues as the white flowers fade to russet. By September, the fall color begins to show on the leaves, and the foliage color deepens to a rich maroon that will keep people guessing what the plant is.
• Roses own the summer. Considered a romantic flower for centuries, roses are one of the most admired summer-flowering plants. In the recent past, hybrid tea roses have been bred that will continue blooming all season if the flowers are pruned as they fade. Shrub roses like “knock outs” are special, because they are disease-resistant, have stunning flowers that bloom every five to six weeks until the first frost, and are winter-hardy and heat-tolerant. If unpruned, the knock out can quickly grow to be more than four feet tall and wide. Periodic trims will keep them as a smaller plant. For maximum performance, a once-a-year cut is recommended (about 12-18 inches above the ground) in early spring after the last hard frost. Plant individually among other shrubs, annuals and perennials in mixed beds and borders. Utilize in drifts of complementary colors for impact to create a formal rose garden. In this manner you can plant shrub, floribunda, miniature and hybrid teas massed in groups that will flower all summer.
• Summersweet (Clethra alnifolia) is late to leaf-out in spring but makes up for it with summertime flowers. It infuses an intoxicating fragrance into the air with its panicles of white fragrant flowers in July and August. It’s a shade-tolerant native shrub that performs well in moist soil. The species grows to about 10 feet high and wide, but the hybrid named “Hummingbird” will stay low, compact and produce many flowers.
• Virginia sweetspire (Itea virginica) has reddish-green stems and arching limbs. It is an extremely handsome native shrub with fragrant white flower spikes. Some people call it the firecracker plant, because flower spikes seem to spread in every direction. The thick leaves add body to the shrub, which spreads by rhizomes throughout the growing season, forming dense colonies. It develops a beautiful, deep-maroon fall color that persists until the leaves drop. It thrives in wet or dry conditions. My favorite hybrids are “Henry’s garnet” – growing to six feet — and “Little Henry,” growing only three to four feet.
• Sourwood (Oxydendrum arboreum) is another of my favorite small, flowering trees. It is late to leaf-out in spring, but it flowers between June and July with white blooms covering the tree when they are least expected. Although it is a native tree, most people don’t recognize it because of its underuse in the landscape. Flowers persist on this 25-foot-tall tree until the foliage begins to turn a deep orange-red in fall.
Joel M. Lerner is president of Environmental Design in Capitol View Park, Md.