Dear Neil: I planted a desert rose in my yard this past year. I thought I had it protected, but it looks like winter got it. Will it come back?

A: Desert rose is winter-hardy only down to about 35 degrees F. That means that it suffers chilling damage even above freezing. Unfortunately, your plant is almost assuredly gone. What I would suggest in the future, as you try a new plant, is that you grow it in a clay pot and sink that pot flush with the soil surface. That will allow you to lift it in the fall before it turns really cold and bring it into a sunroom or greenhouse setting for the winter.

Dear Neil: Our lawn is being overrun by oxalis. Two different highly respected nurseries have recommended what I was told was the best-selling broadleafed weed killer in America. It actually contains three different herbicides. I tried it for the first time last summer and it ended up killing more of my lawn grass than oxalis. That mistake is on me, as it warned me in the instructions not to use it when it was hot. I used it another time last fall when it was cooler, but even though it didn’t kill any grass it also didn’t do much good on the oxalis. Do you have any suggestions on how I can get rid of this weed?

A: You are referring to Tri-mec. It has been one of the most successful blends of weedkillers in the many years that it has been sold. My experience in using it has been that it works better when applied with a pump sprayer instead of one at the end of a hose. I also include one drop of liquid dishwashing detergent in each gallon of spray that I mix. That allows the smaller droplets to coat the waxy leaves more uniformly. I’m also careful not to mow for two or three days before or after application. You want to give the herbicide enough time to be taken into the leaves. Sometimes you have to treat more than once. The seedpods of oxalis actually explode when they are mature, and that sends seeds many feet in all directions. It’s possible that you have been seeing seedlings weeks or months after you killed the mother plants.

Dear Neil: Each spring caterpillars devour my Texas mountain laurel until I notice they are eating away and I spray B.t. Last year I didn’t see they were there until they had stripped half of the tree. They work very quickly. Would it be possible to spray before they arrive? And will my tree fill in where the leaves were eaten?

A: You’re referring to the larvae of the Genista moth. And, yes, they feed voraciously. You might try a systemic insecticide applied several weeks in advance of when they typically arrive. However, I am much more comfortable recommending that you merely check the plant every day. While it may seem like they feed overnight, you will have several days in which to treat before they get out of hand. As for whether your plant will fill in, it does look a little rangy. However, it also looks like it’s in a good bit of shade. That’s not a good thing for Texas mountain laurels. They need full sun. If it were my plant I might trim it back a good bit and try to get it to fill in, but I really can’t see it well enough to tell you for sure.

Dear Neil: I have chickweed all over my rose bed. I applied Gallery broadleafed pre-emergent weedkiller last fall. Either it was the wrong material, or I might have applied it at the wrong time. What can I do now?

A: At this point I would use a line trimmer to remove all the existing chickweed. Be careful not to damage your roses’ stems. Then I would come back with a layer such as pine bark or hardwood mulch to cover the bed now. Around Labor Day of this year I would apply 1 inch of additional mulch, and then I would apply shredded tree leaves as they fall in November. That way you don’t have to apply any kind of weedkiller around your roses, and the mulch will discourage germination of the chickweed seeds.

Dear Neil: We have several large fire ant mounds in our yard. The mounds do not appear to contain live ants, but when we disturb the mounds, ants come to the surface. We have noticed them all around the yard, in flowerbeds and around the trunks of trees. Is there a best way to treat for fire ants, and when should it be applied?

A: Look online for the “Texas two-step method of fire control.” You will find detailed instructions on areawide control using baits and also individual mound treatments. There are very effective products on the market. In my own personal experience, when I use the baits once or twice a year, I rarely have to use the individual mound treatments. The reason you see the mounds at this time, but you don’t see active foraging ants is because the mounds have been cold and the ants have remained in the warmer soils below.

Dear Neil: I have heard that each spring one should trim back Asian jasmine to promote new growth. Should that also be done to Persian ivy? How can I start more Persian ivy?

A: It’s not necessary to trim (mow) Asian jasmine in late winter unless the jasmine has been damaged by the cold or unless it has become ragged and uneven in its growth. I would probably never trim any of the ivies in that way. Propagate them by taking short cuttings with two or three leaves and sticking two or three cuttings into each 4-inch pot filled with loose, highly organic potting soil. That should be done in the fall, and the pot should be put into a bright, warm greenhouse for the winter.

• If you’d like Neil Sperry’s help with a plant question, drop him a note in care of The Eagle, P.O. Box 3000, Bryan, Texas 77805. Or email him at mailbag@sperrygardens.com.

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