Q. I have dollar weed in my St. Augustine lawn, and it's crowding out the lawn. What will control it, and when should I apply it?

A. Use a broadleafed weedkiller spray containing 2,4-D. You'll need to read and follow label directions carefully to avoid damage to desirable plants nearby.

However, if you apply it carefully with a pump sprayer set to deliver a fine mist, and if you include one or two drops of a liquid dishwashing detergent per gallon of spray to help the herbicide hold tightly to the leaves, you should see good results.

Q. What causes a thick, white substance to form on the surface of plant leaves? It ends up looking like the icing on a donut.

A. That's honeydew that has congealed and crystallized. It's produced by several types of insects, including scales, whiteflies and aphids. It's really not a huge cause for concern, but it's disfiguring. In many cases, black sooty mold will also grow within it, making the plant even less attractive. Wait for new leaves this spring. Prevent future episodes by treating for the insects as needed.

Q. We recently had a very large live oak (4-foot soil ball) planted in our landscape. What should I do to ensure its success?

A. Several things will help. Some may have been done at the time of planting. First, stake and guy the tree so that it cannot tilt. There are occasions when that won't be needed, but it's better to be safe than sorry. Wrap the trunk with paper tree wrap from a nursery or hardware store. Wrap it from the ground up to the lowest limbs, and leave the wrap in place for one to two years. It will protect the trunk from sunscald and borer invasion. Soak your new tree deeply on weekly intervals during spring and fall, five-day intervals in the hottest part of the summer. Apply a root-stimulator fertilizer monthly for the first year or two.

Q. I'm trying to get a head start. How can I get my Bermuda grass to green up this summer? I used iron on it last year, but it didn't help. I've noticed that the part near the roots was brown and the top a little more green. It is in full sun. What can I do?

A. The most common cause I see of browned Bermuda grass comes from mowing too high. The optimum mowing height for common Bermuda is 1 to 1/2 inch. If you mow it higher than that, the grass will become weakened and you will probably be able to see through the turf to the runners and soil. If that might be the cause, scalp your lawn in the next three to four weeks by dropping your mower blade down to that height. You will remove all of the dead stubble in that process, and that will allow your bermuda to green up quickly as warm weather returns. In terms of nutrients, bermuda rarely needs iron, but it always needs nitrogen (first number of the fertilizer analysis). Time your feedings to be 8 or 9 weeks apart beginning in late March or early April and continuing until early October. Those steps should give you greener grass. Bermuda should grow well almost anywhere that there is full sun.

Q. I have noticed a thing that looks like a cork shelf growing on an old oak tree in our yard. Is this something that might spread to other trees? Will it kill oaks?

A. That's a bracket fungus of one sort or another. It is saprophytic, meaning that it lives off dead and decaying organic matter, not off living tissues. However, the fact that there is dead tissue around the bark does suggest that the tree has some kind of issue. So, while the bracket fungus won't kill a tree, the problem that invites the fungus certainly could. I'd suggest you contact a certified arborist for an on-site exam.

Q. I have not been satisfied with my rose of Sharon shrubs that I planted to be a screen. I thought they would grow quickly, but they are still spindly and short. Do I need to prune them? Should I fertilize them? Should they simply be moved?

A. Roses of Sharon are lovely summer-flowering shrubs. They do vary a good bit in their mature height and growth form, however, so be sure you planted a type that has the genetic potential to grow as tall as you had hoped. Pruning will not help, other than perhaps to get the plants to thicken up. Apply a high-nitrogen fertilizer in early spring and again in early fall. Whether you move them yet this winter or not will be up to you. You should remember, however, that these are deciduous plants, so to use them as a screen still leaves four to five months that they would be bare.
