Ask the tree doctor - gardening - Brief Article

American Forests, Wntr, 2002

Don't know when to purne? Curious about lobed leaves? Have no fear--the Tree Doctor is here.

Q: I am an amateur at tree enjoyment and was wandering if you have a recommendation on a book/site that would help.

Vic DeCarlo

Via e-mail

A: A good book to start with is the old favorite "Little Golden Book of Trees." Study the sections on leaf characteristics, branching types (opposite or alternate), bark patterns, and so forth, and try to absorb some of the language used to describe the differences among species. Then get out there among the trees and go to worklMost any good bookstore has a variety of books expounding on trees. For beginners, my only caution is to not go too deep, too soon; learn native species first. Here s a couple of short cuts: Learn to separate red oaks from white oaks as groups, and worry about learning the different species within each group later. Same for hickories. If you get stumped, call your nearest forester or local horticulturalist for help.

Q: My wife asked me if, as a tree grows, the bottom branches move up with the growth. I said the growth is from the top and branches stay the same distance from the ground. Please give me your answer; am I right?

Don Gerken

Via e-mail

A: At the risk of offending your spouse, I have to say you are correct. Tree growth is from the top and the branches elongate, but cannot move upward. If you think of a tree as an upside down ice cream cone with a toothpick stuck in it to represent a limb, and each year's growth as an overall added layer of waffle, you can see that it gets higher, but any blemish on the cone will stay where it is.

Granted, the toothpick will get thicker, but it can't go higher. To prove this to doubters, measure a tree's total height and the height of a limb above ground, and then do the same thing a year from now. The limb will probably be larger in diameter, and the tree higher overall, but the limb will not have advanced upward.

Q: I am the gardener at Locust Grove Historic Home (home of George Rogers Clark, explorer and brother to William Clark of Lewis & Clark fame). We have an American elm (200+ years) that has had, and perhaps is still suffering with, Dutch elm disease. Two years ago tree surgeons did a drastic trim and shot the ground with medication, but we are noticing new distress. I am wondering if elms respond to softwood cuttings, as nobody has ever seen a single seed or seedling from this tree, and if such a sprout could be successfully medicated to eliminate the disease.

Sarah Dickerson

Louisville, Kentucky

A: Jeff Meyer of AMERICAN FORESTS' Historic Tree Nursery confirms that traditional nursery practices do not provide the know-how to reproduce an elm from cuttings. It might be possible in a laboratory but at considerable expense, and there is no way to protect cuttings from Dutch elm disease. Better to turn your thoughts toward enhancing Locust Grove after the elm succumbs. Perhaps local tree people can keep it going long enough to give you a cushion of time in which to get replacement trees established. Some, like the zelkovia, look much like elm; some nurseries can also find a few disease-resistant elm varieties. Or, consider contacting Jeff at jmeyer@histarictrees.org to see if he has some historic tree seedlings related to the Lewis & Clark expedition, which might add to the quality of visitors' experience.

Email questions for the Tree Doctor to mrobbins at amfor.org or write: Tree Doctor/Pubs, AMERICAN FORESTS, P0 Box 2000, Washington, DC 20006.