Q: We have a lovely xeriscape garden that has been invaded by what we are told is a relative of purple heart. It has small blue flowers, and it sprawls over our plantings. How can we eliminate it?

A: That sounds like our native spiderwort, and it is, indeed, a cousin of purple heart. Like its relative, it roots easily from stem clippings, so when you dig or pull it, you will have to be sure that all roots and stems come along. There is no herbicide spray or granule that can be used to eliminate it without risk to your desirable plants nearby. However, you could try painting a 2,4-d weedkiller on with a foam rubber brush. I have this weed in my own beds from time to time, and I always dig it out.


Q: We have a collection of aggressive weeds growing in our yard. They look somewhat like maples. What are they, and how can I stop them?

A: You have a very common volunteer tree. This is juvenile foliage of mulberry trees. As they grow taller, the lobed leaves will give way to rounded leaves without lobes (typical mulberry leaf shape). These are seedlings of a fruiting mulberry, and they, too, eventually will produce fruit. You can hoe them out, or, in open spaces, you can apply a broad-leafed weedkiller.

Q: We have a 12-year-old red oak that has always been lush. This year, the foliage is sparse, and there is a big acorn crop. Is the thin foliage because of the drought?

A: Yes, unless there are other issues that have cropped up with it in the past 15 months. I received a similar letter from someone with a walnut tree question, also related to drought. Anyone who has a tree that did well for many years and developed a problem after last summer needs to suspect drought damage first and foremost.

Q: What would kill an apricot tree almost overnight? I have another tree that is still healthy.

A: It could have been an attack of peach tree borers. Check the lower trunk, just above the ground, for globs of congealed sap coming out of the borers' tunnels.

Unfortunately, there is no reliable way of getting them out of a tree. It's even difficult to keep them out of the trunk in the first place. The other possibility would be cotton root rot, a soil-borne fungus. It's present in alkaline soils, and it behaves exactly as you described. Hopefully it won't migrate within the soil to attack the other tree.

Adding large quantities of sulfur soil acidifier might help protect the surviving tree, but results aren't always perfect.

