Tree Doctor Howard Burnett.

Q: I have two questions: Is Ginkgo biloba native/naturalized? And, if, as the tree grew, its roots lifted the ground level, does the 4.5-foot measurement still take place where the tree meets the soil?

D. Mikola via e-mail

A: Ginko biloba has been planted widely but is not a native. It came to us from the Orient, probably China, many years ago. The standard measure of diameter, "Diameter at Breast Height" (DBH) is taken 4.5 feet above average ground level. The only recognized exception is on National Forests, where it is taken from highest ground level, as this seemed more fair to purchasers of timber trees who could not leave a stump at "average" ground. Although your case is unique, I believe the 4.5-foot rule, to be taken from the average ground, would still apply.

Q: I have seedlings from the American elm "Survivor Tree" in Oklahoma City. At present there are three in a pot in the house. I rent an apartment and would like the seedlings to survive long enough for me to find them an appropriate home. Do you have seedling care tips for the person who does not have a green thumb?

Terry L. Norton via e-mail

A: I would put each seedling in a separate pot and be sure it drains so water does not waterlog the soil. Reasonably good soil should be good enough, as this is what Mother Nature has to work with. Over-fertilization should be avoided and shouldn't be necessary if the potting medium is pretty good to start with. As far as an out-planting site, the sooner you can get them there, the better. Keep them in the pots until December or so, when they are dormant for the winter and root damage will be lessened. If the seedlings are to be kept outdoors, watch that nothing chews or otherwise attacks the, but don't go overboard with insecticides or fungicides. I assume the Survivor Tree is from the Murrah Building Plaza area, and I do hope its progeny can be out-planted as a reminder that bad things can happen here at home, as well as abroad, too.

Q: We are coffee planters in the Western Ghats, India. Silver oak is grown in between the coffee plants. The terrain is rocky and we have patches where the soil depth is insufficient. Some of the existing trees 4-7 years old seem to be undernourished due to these conditions. I would like to relocate them to a better environment. Is this possible?

Vishalla Vairavan via e-mail

A: Moving or transplanting any kind of tree requires careful attention at three points: Lifting it from its current location, transporting it to its new location, and planting it in its new site. When digging up the tree, try not to damage the root system any more than necessary. Get as much soil as possible and enclose the root ball in a porous wrap, like burlap cloth. Get as much of the root system as possible and keep the roots from drying out. The larger the tree, the heavier the root ball, so have adequate labor at hand. If you're moving the tree very far, wrap it to keep the branches from being dried by wind or air. At the planting site, dig a hole about twice the diameter of the root ball. The root ball should be set on firm soil, and good soil firmed up in the remainder of the hole. The tree should be set at about the same depth in the ground as it was in its former site. The burlap wrapping can be peeled back and left; it will eventually rot away. The tree will need lots of water to help the root system become well established. Watering may go on for several years. Remember transplanting is best done during a tree's dormant season.

Q: If I prune an American holly bush down to the trunk will it grow back? Here in Tennessee we have not had any hard winters to the point where the ground really freezes. The insects are extremely bad in spring and summer. The hollies are in front of my porch on each side of the steps and are actually hedges now. I am unable to sit on my porch because of red wasps. I don't want to kill the bushes, but the only thing I can think of is to cut them back. What can I do?

Pam Burnett via e-mail

A: Hollies can be shaped and pruned, but I do not recommend "topping" them. Pruning to expose the trunk to sunlight will result in sprouting along the trunk, and those new sprouts will, in time, fill out the holly's shape again. In time, they can become trees higher than your porch, if a leader is encouraged. Holly has flowers, though they are not very conspicuous. The wasps and other insects are getting their share of nectar, in return for pollination that leads to berries. I have never known insects to be a threat to people, unless we sit on them or otherwise upset them. They will pretty well ignore people sitting nearby. I hope you can manage to live with the wasps during flowering season and continue to enjoy your beautified entrance walkway.

Q: I have a small-leaf linden that is 40-50 feet tall. Last year I noticed branches stripped bare of bark. I am noticing more branches in this condition this year. Is this indicative of a problem? And if so, what is the solution? About three years ago my husband built up a 10-15 foot circular, soil-filled base planted with pachysandra, hostas, and bulbs that ranges from ground level to about 2 feet deep as the tree is on a slope. I've since read trees don't care for this. I hope we haven't damaged the tree.

Dawn S. via e-mail

A: Some top die-back in your linden may well indicate a disturbance in the root system. The planter, like any change in ground contour, can affect the soil moisture balance, and roots can be either drowned or dried to the point that they are unable to keep up their fair share of the work. I recommend you contact a certified arborist in your area (http://www.isa-arbor.com/findArborist/findarborist.aspx) to have a look at your tree's situation and see what can be done. It may well be that some root feeding outside of the planter will help the tree overcome the problem. On the off chance there might be a disease or insect infestation responsible for the die-back, the arborist will be able to recognize that, too.