Dear Neil: When is the best time to prune back my rose bushes that have grown too tall? I think it’s during the winter. How do I do it? Also, please tell me about the rose rosette virus.

Prune immediately. In South Texas roses should be pruned during the first two weeks of February. In Central and North Texas, they should be pruned by the middle two weeks of February. Prune bush types by 50 percent. Thin out all weak, non-productive branches and canes, and make all cuts on the remaining stems just above buds that face away from the centers of the plants in an effort to open them up, to encourage outwardfacing new shoots.

While you’re pruning, pay attention to whether you see any evidence of rose rosette virus. It’s a fatal virus that can neither be prevented nor cured. It is spread by a microscopic, wind-blown mite. The virus causes plants to grow quite erratically at first. Some shoots will be very vigorous. They’ll be twice as tall and thick as other, normal canes, and they may have eight or 10 times the normal number of thorns. Flower buds will form, but theywill not open properly. Within a year the plants will become weak and start to die. The only thing a gardener can do is to remove infected plants, roots and all, the moment it is observed. I do not recommend replanting roses in that neighborhood until better news comes from research.

Dear Neil: My backyard turf has grown thin over the past several years. I’m thinking it needs to be aerated. I also want to raise the level of the backyard. How much soil can I add to the top of the lawn per year? How many times per year? What type of soil should I add?

Lack of aeration would not have caused your grass to become thinned. I have both St. Augustine and Bermuda grass growing in a heavy clay soil, and I have never felt the need to aerate. Only if you have a proven accumulation of thatch or have had extreme pedestrian traffic in an area should aeration be considered. As for adding soil, I could go along with adding up to 1/2-inch of washed brick sand to low areas such as ruts where someone has driven into your yard, but I would not try to save the existing turf if you’re planning on adding several inches of soil to the landscape. Be very careful, too, that you won’t change drainage patterns in the process, bringing water into your house or garage.

Have a question you’d like Neil to consider? Email him at mailbag@spertygardens.com. Neil regrets that he cannot reply to questions individually.