My son had beautiful, big willow oaks lining his gravel driveway until he put down a weed killer on the driveway weeds. Now the oak leaves have browned on the tree halves facing the driveway. What can we do at this point to save the trees?
What a profound aesthetic, environmental and monetary loss. Several herbicides on the market have ingredients that readily travel down through the soil profile. When applying them, it's crucial to remember that the roots of a tree can extend out as much as 11/2 times the height of a tree. Labels always must be read carefully. At this point, contact the herbicide manufacturer and/or the National Pesticide Information Center (800-858-7378) for remedial possibilities. If you need a tree service company, we recommend one with an arborist certified by the International Society of Arboriculture. Go to "General Interest" in our website links to find one.
My Kwanzan cherry tree bloomed beautifully this year, and then suddenly, leaf clusters started wilting, browning and dropping off. This occurred throughout the tree, but the lower part was affected more than the upper. They curl a little like the "shepherd's crook" that fire blight causes, but only apple trees and pear trees get fire blight, right?
You're right, your cherry tree does not have fire blight. Your Kwanzan cherry has brown rot. Before the past few years, this fungal disease did not infect ornamental cherries at all, but now it infects Kwanzan cherry. Brown rot normally targets fruit trees such as cherry and peach, requiring a rigorous spray schedule in order to produce edible fruit. It is too late to treat your tree this year. Infection began when the tree was blooming. Because this form of the disease is fairly new, we do not have a lot of information on it. It seems to target smaller branches first, can cause some dieback and eventually may target larger branches. Thinning out the tree canopy will increase air circulation and faster drying after rain. Moist leaves promote fungal diseases. Prune the tree when the weather is dry to prevent spreading the disease.
University of Maryland Extension's Home and Garden Information Center offers free gardening and pest information. Call 800-342-2507 or send a question to the website at extension.umd.edu/hgic.
Plant of the Week
Clematis x Jackmanii
Varieties of clematis come and go, but Jackmanii is a timeless beauty found in gardens since 1862. The lush, velvety deep purple flowers fill the vine from June through August. Jackmanii (pronounced Jack-man-e-i) is a vigorous vine with few pest or disease problems and can eventually reach 12 to 20 feet. Support it with a trellis, pergola, fence or lamppost. Train it through a shrub or small tree to increase their seasons of interest. Site in sun to partial shade, in fertile slightly alkaline, well-drained soil. Plant it deeply and protect and shade the roots with mulch or a groundcover. This clematis is classified in Group 3 for pruning specifications. Prune and fertilize in late winter or early spring. Deer do not tend to browse on clematis. — Debbie Ricigliano