Q. I’d love to plant an American flowering dogwood, but I understand that they are very susceptible to diseases. Is this true?
The American dogwood (Cornus florida) is highly susceptible to a fungal disease called dogwood anthracnose. First noticed in the Northeast in the 1970s, it has recently become a less serious threat. Symptoms include spotting and blighting on the leaves, dead branches, and eventually the death of the tree. If you already have a dogwood, keeping it healthy is the best preventive step. Planting in full sun is helpful. The trees should be well watered during dry spells, and mulch should be applied around them.
A related species, Japanese dogwood (C. kousa), is relatively resistant to anthracnose and can be planted as an alternative to the American dogwood. Unlike the American species, its "flowers" (which are actually bracts--the flowers are the tiny green clusters at the center of the pink or white bracts) don’t appear until after the tree has leafed out. Nevertheless, C. kousa is a very attractive small tree.
Fortunately for gardeners who want to stick with the American dogwood, several anthracnose-resistant varieties have been developed. ‘Appalachian Spring’ is a variety of C. florida which was discovered growing naturally in the woods in Maryland and is now widely available. It has white "flowers."
Dr. Elwin Orton at Rutgers University has developed a number of disease-resistant hybrids (between C. florida and C. kousa). These are known as the Stellar Series®, e .g. ‘Constellation’,‘Aurora’, ‘Galaxy’,‘Stardust’, and ‘Ruth Ellen’. They are all basically white with some differences in flower color, growth habit, flower shape, and hardiness. Dr. Orton has also introduced ‘Stellar Pink’ with pinkish bracts.
Recent introductions from the same source are ‘Hyperion’, which is extremely vigorous with attractive white flowers, and ‘Red Pygmy’, a rare dwarf variety with pink-red bracts tipped with white.
It should be noted that powdery mildew is becoming a more serious problem in dogwoods. Although this disease is less lethal than anthracnose and more of a cosmetic problem, it can become serious. Powdery mildew can be treated with fungicide sprays.
For tips on a variety of gardening topics, see our Plant Information Guides.
- Courtesy of NYBG Plant Information Service