Kousa dogwood summer foliage

Chinese (Kousa) dogwood (Cornus kousa) rates four stars (out of four) as a beautiful small flowering landscape tree. Since the 1970’s, a deadly anthracnose (Discula spp.) fungus disease has threatened to eradicate our native flowering dogwood (C. florida). Kousa dogwood rates as a highly disease resistant alternative. Its Achilees’ heel is its less than stellar foliar heat tolerance.

In the Southern Appalachian region (USDA zones 6 and 7) most kousa seed-produced cultivars do not handle summer heat issues well.  Leaves curl up and reduces photosynthesis. Leaf tips and edges may also scorch. Many of the 100 + kousa cultivars listed in Cappiello and Shadow’s book on dogwoods* are not heat tolerant in the mid-South.

Newly-planted trees are both heat and drought susceptible and should be irrigated the first two years after planting. Cooling the soil by watering helps. Irrigate weekly from mid-June thru early September when summer temps are consistently in the 90’s and natural rainfall is deficient. Drip irrigation keeps kousa foliage dry and disease free while conserving water usage.

A number of U.S. nurseries are currently evaluating several, still unnamed, seedling selections which may be more heat and drought tolerant in the Southeast U.S. landscapes. Expect to see a few at local garden centers in the next 4 – 5 years.

* Cappiello, Paul E. and Don Shadow. 2005. Dogwoods. Timber Press. Portland, OR