Q: When is the best time to cut back verbena? Two years ago, when I planted it in the spring, it bloomed beautifully all summer. I did not cut it back because I wanted it to fill a space. This summer it did not bloom as well as the year before. However, I now need to cut it back. Do I do it now or the beginning of spring?

A: The salient fact about verbena is that it blooms exclusively on the tips of new growth. My observation is that verbena spreads and blooms profusely the first year but looks rather ratty the second year. This seems to be because the verbena branches do not root very well as they extend. Without a good connection to the soil, little fresh growth is produced.

You can fix the situation by trimming the whole area to three inches tall sometime between now and March. In addition, use a shovel to chop through the mat of stems in several places to stimulate new growth at those spots. It would be nice to lightly cover the brown stems in the center of the clump with compost. This will further encourage growth. You’ll have the brilliant purple blooms you admire from April to October once again this year.