My old friend Von Woods sent me a question a few weeks ago that made me do a little research. “Do you have a list of dogwoods that are disease resistant?” he wrote, “I’ve heard that a new fungus is killing a lot of the wild trees in the Smokies.”
Von’s information is true, but it’s not time yet to hit the panic button in Atlanta. Discula destructiva has killed thousands of native dogwoods along the Atlantic seaboard. Fortunately, scientists have observed that most of the infected trees occur on elevated mountainsides and on dogwoods growing in heavy shade. That means that most of our trees, both landscape and woodland types, are reasonably safe.
Researchers began testing for discula resistance in the early 1980′s. They found that although our native flowering dogwood (Cornus florida) and the Korean dogwood (Cornus kousa) are susceptible to this disease, their inter-species hybrids are not. In other words, when native dogwoods were crossed with Korean dogwoods, their offspring could fight the disease to a standstill. Rutgers University has released several of these patented, disease-resistant dogwoods, including ‘Stardust’, ‘Stellar Pink’, ‘Celestial’ and ‘Constellation’.
Even with the availability of disease fighting hybrids, I wouldn’t hesitate to plant less disease-resistant dogwoods like the white-flowering ‘Cherokee Daybreak’, ‘Cherokee Princess’ and ‘Cloud 9′ or the pink-flowering ‘Stokes Pink’, ‘Cherokee Chief’ and ‘Cherokee Sunset’. Although discula disease has appeared in scattered spots in Atlanta, most of our dogwoods are planted in enough sunshine to keep the leaves dry and fungus-free.
The factor that determines, more than any other, how well a dogwood will fare is the availability of moisture in summer. If your trees are growing in full sunshine, be sure to water them once per week when drought is upon us. Additionally, a thick layer of mulch spread under the tree out to the ends of the branches will keep the soil cool and conserve what moisture is in the earth.
COLD HARDINESS Clint Hasty, up in Cumming, is trying to avoid hearing “I told you so!” due to a lack of research. He writes:
“My wife and I purchased six wild potato bushes last summer at a local home improvement store for $36 each. The tag said it was a hardy plant down to -10 degrees. They were beautiful shrubs with hundreds of small purple flowers on them. After our first frost they lost all their leaves. My wife thinks they all are dead but I keep telling her they will come back in the summer like a crepe myrtle. Please tell me that I am right; I am not sure what this plant does throughout the year.”
Whew! I can just imagine the worried look on the missus’ face as they shelled out over $200 in one landscape plant purchase. But SURELY a store wouldn’t sell a plant that isn’t winter hardy here, would they?
Despite Clint’s memory of the plant’s information tag, potato bush (Lycianthes rantonnei) is not winter hardy outdoors here. It is grown in many other warmer spots in the country but it just won’t survive an Atlanta winter. If Clint still has the plant tag, he should show it to the nursery manager and ask for a refund.
As planting season gets into full swing, make sure you know a little bit beforehand about the plants you buy. Unless you are positive about their growth habit, pest resistance and hardiness, ask a knowledgeable gardener or nursery person to advise you. Personally, I find “The Southern Living Garden Book” to be a comprehensive and easy-to-use reference to most of the plants you could consider growing here.