Have you ever looked up in the tree canopy to look for flowers in summer months? Some trees flower in the summer. There are fewer trees that bloom in July and August. Summer beauty can be enhanced by adding a native summer-flowering tree. Take a look at the Kentucky’s Sourwood tree Oxydendrum arboreum. These are a delight to the landscape and flower in summer.
One tree that is a July bloomer with the added benefit of being native to our Commonwealth is the Sourwood tree Oxydendrum arboreum. Not only is there beauty in summer from the delicate flowers, but also there is a lovely shade tree from the mature Sourwood in the landscape. This is a deciduous tree. Flowers are small, but fragrant and white. Flowers are visible in masses as they grace the 4- to 10-inch long panicles in July. Once opened, the flowers last for up to three to four weeks, depending on weather conditions. Gardeners are encouraged to look for this tree in the nursery trade. But, be armed with the knowledge that the Sourwood is difficult to propagate for the nursery trade and can be difficult to transplant.
Seek out small, container-grown trees for best results in establishing a Sourwood in the landscape. Follow best practices when transplanting. The soils of Kentucky which are rather infertile and have a pH in the acetic range of 5.5 to 6.5 pH are best. Planting Sourwood at a site in full-sun or part-shade is desired. Allow plenty of space for the tree to grow to maturity. Mature size is a pyramid shape reaching a height of 25 to 30 feet tall and a span of about 20 feet wide. In favored sites, the Sourwood has been known to grow larger than normal. Our local winter-hardiness zone works well since the Sourwood grows in Zones 5 to 9. Once established this tree should tolerate our unusual swings of hotter-than-average summers and warmer-than-average winters. Sourwood is known to survive to -20F so it should also take most any winters which colder-than-average, if a good root system has been established.
Sourwood has another surprise. The fall color of Sourwood’s deciduous leaves is delightful since it is one of the trees which can have red-to-maroon leaves in the weeks of peak color. Commonwealth gardeners are encouraged to plant more Sourwood trees. There is an opportunity to increase the landscape with Sourwood.
Sourwood as its name indicates, prefers the acid soil also favored by azaleas and rhododendrons. This trio makes for a complementary planting to have color from early spring into the fall. Consider adding to the July-August landscape by increasing the abundance of summer-flowering trees, especially the Sourwood.
Submitted by Kathryn Wimberley, Agent for Horticulture, McCracken County Cooperative Extension Service