Ask a Gardener (March 2021)
We received a lot of questions from our members in March. If your question isn't addressed or isn't fully answered below, please feel free to call Judy directly. Send "Ask a Gardener" questions to Susan via email before the first of each month, and she will get answers from Helen and Judy, our resident experts.
Question: When the best time to prune wisteria? Judy's answer:
Prune the tendrils all summer long to reduce crazy growth. In the fall, prune to work on structure. It is helpful to look at pictures online. Or better yet, go to the Huntington in summer and fall to see how they are pruning their wisteria in the Japanese Gardens. Question: When is the best time to divide, plant and purchase iris? Judy's answer: Every three years, divide and replant iris in June, July and August after they bloom. You want to make sure that the roots have ample time to grow before winter. You can usually tell that your irises are ready to be divided when a clump looks overgrown, with rhizomes starting to grow into each other and popping up from the soil. Replant so the top is slightly exposed. If you don't divide, cut down the fronds. Iris catalogues typically are available in late summer to early fall. Question: What should I do about the millions of grubs in my raised planter beds? Judy's answer: This is a tough one. It depends on what kind of grubs you have. You can drench the soil with diluted Neem oil. Or you could try using earth-friendly nematodes which seek out and kill grubs and other soil-inhabiting insects. Arbico Organics has a useful website and sells the proper nematodes. You can also get help from them on the telephone by calling 800-827-2847. Question: When should jacarandas be pruned? Judy's answer:
Jacarandas and all trees should be pruned during dormancy before new growth begins. At other times, only remove dead, broken or diseased branches. In general, all of our trees in Southern California are drought-stressed,
so it is better to postpose pruning because the trees don't have enough energy to cope with being cut. And don't forget to deep water your trees because of the drought.