Summer doesn’t have to be a time for shrubs to fade into the background, outshined by annuals and perennials. With careful selection, summer-flowering shrubs can be spectacular additions to the summer garden, offering form, texture and outstanding bloom throughout the hottest days of July and August.
No matter the size of garden, a summer-blooming shrub whether large or small awaits to define the space.
Bottlebrush buckeye, aesculus parviflora, is one of the best large native shrubs available to American gardeners. Dramatic spikes of creamy, bottlebrush-like flowers in early summer are attractive to butterflies and hummingbirds. It grows to 10 feet high and wide, so give it plenty of space (and sun) to grow.
The shrub weeps the first year, creeps for a year or two, and then leaps. Not much happens the first few seasons after planting as the roots grow out from the planting hole. Once established, bottlebrush buckeye suckers at the base, forming a dramatic colony covered in flowers in summer. Plant in sun or partial shade in moist, well-drained soils.
A native of China, butterfly bush, buddleia davidii, offers what few other shrubs can: summer-long bloom and fragrant flowers that butterflies can’t resist.
In our region, butterfly bush typically dies back to the ground in winter, then pushes out gently arching branches with long, cone-like flowers on new growth. The fragrant flower clusters are butterfly magnets, making this plant a natural addition to the wildlife or butterfly garden.
‘White Profusion’ blooms in pure white, ‘Black Knight’ has deep purple flowers, or try ‘Pink Delight’, with light pink flowers.
Butterfly bush typically makes a massive statement in the garden, growing to six feet or more over a single summer. Newer, smaller selections of butterfly bush are available, such as the Adonis Blue butterfly bush with deep blue flowers on a bush that grows to about four feet.
Blue-spirea, also commonly known by its genus name caryopteris, is a low, mounded shrub that comes alive in the late summer and fall garden.
Fragrant, silver foliage covers the plant during summer. In late summer, clusters of small blue flowers are formed where the leaves meet the stems on the outermost branches, lasting for several weeks and relished by pollinators. Flowers are formed on new wood.
Caryopteris is considered a sub-shrub, meaning it should be cut to six inches in early spring like a butterfly bush. It grows best in full sun and well-drained, poor soils. Excessive fertilization causes the plants to outgrow the site.
This native shrub produces slender spikes of fragrant flowers in July. Shiny green leaves grace the shrub throughout the season, adding textural interest to the garden. Clethra, clethra alnifolia, is well-suited for sun or shade, but performs best in sites with moist soil. Given sufficient moisture, clethra will sucker from the base, forming shrubby colonies.
Clethra can reach to heights of about eight feet in the garden, making it useful at the back of the shrub or perennial border. Shorter introductions offer the typical flowers and fragrance of clethra on a more diminutive shrub that can be used throughout the garden. The cultivar ‘Hummingbird’ is a more compact selection that has deep green leaves, good fall color and a mature height of about four feet. ‘Ruby Spice’ is a larger selection with light pink flowers.
Seven-son flower, heptacodium miconioides, is a relatively new plant to American gardeners. While it was discovered and introduced by the plant explorer E.H. Wilson in the early 1900s, the plant was not embraced until it was reintroduced from China in 1980 and promoted by the Arnold Arboretum.
Heptacodium is now a popular addition to summer gardens, favored by nursery growers and gardeners alike. The plant has earned itself a prominent spot in many arboreta and botanical gardens, including Secrest Arboretum in Wooster and Kingwood Center in Mansfield.
Seven-son flower begins to come alive in late summer with clusters of small, slightly fragrant white flowers. The flowers are borne in clusters of seven, hence the names seven-son flower and Heptacodium, meaning seven (hepta) heads (codium).
A second floral display comes after the flowers fade, when the flower sepals mature to red, with an effective color display through autumn. This floral display has earned heptacodium the nickname autumn lilac. Exfoliating bark offers winter interest.
With a mature height of about 15 feet, heptacodium isn’t for meek gardeners. The shrub demands a prominent place in the garden where it can attain its mature size. Some gardeners train the shrub into a tree form. For best results, plant seven-son flower in full sun, although it is tolerant of some shade. Young shrubs may need selective pruning to promote even, compact growth.
‘Blushing Bride’ rose of Sharon
Rose of Sharon, hibiscus syriacus ‘Blushing Bride,’ is a reliable summer-blooming shrub, adding color to the garden when most shrubs are well past bloom.
Useful in borders and for hedging, rose of Sharon grows eight feet tall by four feet wide at maturity, and is sometimes pruned to a tree-like form. This shrub grows best in full sun and well-drained soils, but is quite adaptable.
Single and double flowers are produced over several weeks in mid and late summer. Numerous cultivars are available, including ‘Blushing Bride,’ with double white and pink flowers with a darker center. Rose of Sharon will sometimes reseed prolifically, becoming a pest in the garden.
‘Limelight,’ hydrangea paniculata, is an outstanding hydrangea that adds interest to the garden in summer and autumn. Billowy, lime-green flower clusters – some more than 10 inches long – cover the plant in late summer. Flowers fade to white, then finish the season in shades of pink and rose. Limelight is an excellent selection that adapts to many landscape conditions, but blooms best in full sun.
This plant blooms on new wood, and so can be pruned in winter before new growth begins. Left unpruned, this shrub needs plenty of space, since it will reach six to eight feet high and wide. Flowers make excellent cut flowers, both fresh and dried.
‘Gibraltar’ bush clover
This gently weeping shrub covers itself with lavender-pink flowers in late summer, making it a perfect addition to the edge of a water feature or along a hillside walk. Not especially well-known, bush clover is a member of the pea family that can reach six feet in height in a summer, with branches covered with typical pea-like flowers.
‘Gibraltar’ bush clover, lespedeza thunbergii, is a cultivar that was found growing at the old Gibraltar estate in Wilmington, Del. This selection is covered with thousands of pink flowers on weeping stems in late summer, and is truly a show-stopper in the garden. Plants perform best in full sun and poor soils, and are tolerant of drought. Flowers are produced on new growth, so the plant can be pruned hard in winter to maintain a more compact form.
Denise Ellsworth directs the honeybee and native pollinator education program for the Ohio State University. If you have questions about caring for your garden, contact her at 330-263-3700 or click on the Ask Denise link on her blog at www.osugarden.com.