Although the lush green foliage of landscape trees in the summer is attractive, it is possible to find trees that provide additional summer accents. Some trees provide short-term summer color with their flowers, while others add interest to the landscape the entire summer because of the colorful leaves they produce. As you visit the gardens of friends, or public gardens with attractive landscaping, watch for these trees and try to imagine how one of them might provide summer color for your own landscape.
Several trees have been found or selected to provide purplish-colored leaves during the summer. One of the most interesting is a redbud called 'Forest Pansy' (Cercis canadensis 'Forest Pansy'). As with other redbuds, it produces attractive, pink flowers in the spring, before its leaves appear. When the leaves emerge, they are a rich purplish-red color that changes to a greenish maroon as they mature. Since redbuds in good conditions produce new growth throughout the summer, purplish-red branch tips often exist in front of the greenish maroon foliage. From a distance this gives the illusion of a green-leafed tree producing purplish-red flowers all summer. The Rising Sun™ redbud (Cercis canadensis 'JN2') is colorful but in a different way. It produces new leaves which are apricot in color and later mature to shades of orange, gold, yellow and finally lime green, with colors present all at once.
There are tree species that retain their reddish-purple leaf color for the entire summer. Among the small trees that exhibit this trait are several cultivars of Japanese maple (Acer palmatum). 'Bloodgood' is an example of a fairly large Japanese maple that retains its reddish-purple color throughout the summer. In fall, its leaves deepen to a crimson red. One of the hardiest Japanese maples, 'Bloodgood' makes a good accent tree in the landscape and (slowly) grows to a mature height of between 15 and 25 feet. For locations that call for a smaller tree, 'Crimson Queen' is an excellent choice. Achieving a mature height of between six and eight feet, it has finely dissected reddish-purple leaves produced on plants with a graceful, weeping growth habit.
Additional smaller trees with purplish foliage color include several cultivars of ornamental plum (Prunus cerasifera). 'Thundercloud' and 'Newport' are examples of cultivars with purple foliage color and relatively small mature stature (15 to 25 feet). As was the case with redbud, both of these plums produce attractive flowers in the spring. Unfortunately, this species is susceptible to a number of problematic diseases and insects making it somewhat short-lived in the landscape.
'Royal Purple' smoke tree (Cotinus coggygria 'Royal Purple') is yet another small tree with colorful purple leaves. It also has interesting and unusual flower structures that make it an attractive accent in the landscape. Its name is derived from the billows of purple feathery, plume-like seed clusters that follow after its rather insignificant flowers mature. Its leaves hold their deep purple color throughout the growing season and turn scarlet in autumn. This multi-stemmed small tree grows to a mature height of 10 to 15 feet and a spread of about 12 feet. A well-grown smoke tree makes quite an impression in the landscape, since its branch tips appear to be covered with a smokey haze.
Among large trees with purplish leaves, 'Crimson King' Norway maple (Acer platanoides 'Crimson King') is easily grown in our climate. It produces purplish-crimson leaves that retain their color throughout the summer. Achieving a mature height of about 40 feet, it is very tolerant of poor soil and urban conditions. 'Royal Red' is another attractive cultivar with traits quite similar to 'Crimson King.' Although Norway maple is considered invasive in certain areas of the U.S. because of its prolific seed production, 'Crimson King' and other named cultivars produce less than 1% of the viable seed that the species does.
Another unique (and somewhat obscure) member of the maple family with colorful foliage is 'Flamingo' box elder (Acer negundo 'Flamingo'). Its leaves are green in the center, but their edges are pale pink in the spring when they emerge and later fade to white. Unfortunately, the white leaf edges tend to scorch during the intense heat of summer which reduces the ornamental appeal of this cultivar. Unlike the species, it achieves a mature height of only about 30 feet. Although it displays a somewhat coarse growth habit, it is not as unkempt looking as the species.
As mentioned earlier, there are a few trees that provide summer color with their flowers. Among them are golden rain tree (Koelreuteria paniculata), Japenese stewartia (Stewartia pseudocamellia) and southern magnolia (Magnolia grandiflora).
In late June and July, the golden rain tree is sure to attract attention as it produces large panicles of small yellow flowers. This tree has a rounded growth habit and may become fairly broad when given plenty of room. Mature trees often grow to 35 feet in height and nearly as broad. Its large compound leaves also are attractive when the tree is not in bloom. In late summer, papery seed structures which are yellowish green in color adorn the tree for added interest. These structures eventually turn brown and provide some winter interest after leaves have fallen.
Japanese stewartia is another tree that flowers from late June into early July. This rather uncommon tree is very slow growing and makes a good small accent. It cannot be considered a shade tree in our climate. It bears white flowers about two inches in diameter with orange centers which somewhat resemble a camelia. Given its flowers last only for a few days, it does not provide the show of color associated with other blooming trees. However, its exfoliating reddish-brown bark gives the tree added interest, especially in the winter.
Perhaps the most elegant of the summer-flowering trees is southern magnolia. This broadleaf evergreen bears huge creamy white flowers 8 to 12 inches in diameter and pleasantly fragrant. A southern tree, the species is only considered reliably hardy to zone 7. However, 'Bracken's Brown Beauty' (a selection from the species) has proven itself to be winter hardy through the southern part of zone 5. Although its primary show of color comes in late spring, it continues to produce some flowers throughout the summer. Mature trees of the species can grow to a height of about 50 feet in the south. 'Bracken's Brown Beauty' (named for the brownish pubescent on the underside of its large, leathery leaves) is treated as a small accent tree at our latitude.
There are, of course, many other trees that provide special summer interest. A few others that deserve mention include 'Sunburst' and 'Rubylace' locust (Gleditsia triacanthos), 'Tri-color' and 'River's Purple' beech (Fagus sylvatica) and Tiger Eyes sumac (Rhus typhina 'Bailtiger'). While these all are interesting plants, they will attract special attention and are best used as single accent specimens in the average home landscape.
REVISED: July 12, 2021