Q. I have noticed a translucent yellow gum oozing from the trunk of my cherry tree. Is this something I should be concerned about?
A. The gum you are referring to is sap that is oozing and coagulating on the tree trunk. Some trees species have a natural tendency to ooze sap. However, it may also indicate that there is a problem with the tree. For example, cherry trees are susceptible to borers, and the sap could be oozing from holes they have bored in the wood. The ooze may also be coming from an area infected by disease or from a spot that has been wounded. I would check the tree for borer holes, diseased cankers (dark sunken areas in the bark) or wounds. If you see no evidence of one of these, I would assume that the ooze is natural and that the tree is healthy.
Q. I am looking for a small tree that has nice spring flowers and also has good fall color. Do you have any suggestions?
A. There are a number of small trees that have both the beautiful spring flowers and the good fall color you are seeking. I would include dogwood, hawthorn, crabapple, Japanese cherry, and serviceberry in that list.
However, some of them tend to be more trouble-free than others. The most popular Japanese cherry tree is the cultivar 'Kwanzan.' It has a reputation for being short-lived, but seems to grow very well in Baltimore. It has pink flowers in spring and orange-bronze fall color.
Serviceberry is easy to grow, has early white flowers, and excellent yellow, orange, or red fall color. Crabapple trees grow very well here, but it is important to choose a disease-resistant cultivar. They come in a variety of flower colors from white, to pink, to purple pink, or red pink. The fall color of crabapples comes primarily from the yellow, orange, or red fruits, and not the foliage.
Dogwood and hawthorn are also very nice but tend to have a few more health problems.
THIS WEEK'S CHECKLIST
1. Diseased leaves of trees and shrubs tend to fall in late summer or early fall. They should be cleaned up and removed from the yard or destroyed.
2. This is not only the best time of year to seed your lawn, but is also a good time to fertilize. Fertilizer should be spread at approximately 1 pound of nitrogen per 1,000 square feet of lawn.
3. Are you uncertain about what flowers to plant next year? Go see the trial gardens at Cylburn Arboretum and see what did well this summer.
Dennis Bishop is an urban horticulture educator for the Baltimore City office of the Maryland Cooperative Extension Services. If you have a gardening or pest problem, you can call the Home and Garden Information Center hot line (Monday through Friday, 8 a.m. to 1-p.m.) at 800-342-2507. You can also e-mail questions, order publications and diagnose plant problems by visiting the Web site, www.agnr.umd.edu / users / hgic.