Issue: February 17, 2001


Clean up plant residue and grubs

Question:

Should I cut back or pull up last year's mums and snapdragons? Last year I had grub worms in my fescue lawn. Do I need to spray again this year before replacing grass? Vida, Roswell

Answer:

The chrysanthemums are perennials and should be alive below ground. Cutting the tops back before new growth begins is good. It was okay to leave the dead tops in place during the winter because they collect snow to moisten the soil around the roots. They also slow the wind over the plant crown, reducing evaporation. However, there is a slight chance that they can be a source of disease entry into the plants once the weather warms and growth begins. The dead stems are also unattractive so the planting will look neater if these dead stems are removed. Cut them with sharp pruning shears; don't try to pull them out.

The snapdragons may have survived the winter, but they may also have died. Cut the tops back before growth resumes, if it resumes. You may find that seeds which fell from the plants have germinated, so even if the old plants didn't survive, you may have new plants to replace them. If the old plants did survive, they can have problems with rust fungus in their second year so some gardeners dispose of them and don't leave them. They either rely on the newly developing seedlings or they buy new plants. As stated before, if you want to leave the plants, cut the dead tops off with sharp pruners; don't try to pull them off.

Finally, regarding the grub problem, you may need to spray again, but this should be done in early August if you are using most traditional grub control chemicals. Do this only if you find grubs in the lawn. To directly answer your question, no you don't need to treat with chemicals before replacing the fescue, but you may need to treat afterwards. The grubs should do relatively little feeding in the spring before they pupate. Once they pupate (begin the metamorphosis from grub to beetle) they will not eat. It is the newly hatched grubs in August that may damage your replanted fescue.

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For more gardening information, visit the NMSU Extension Horticulture page: desertblooms@nmsu.edu.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, office: 505-865-7340, ext. 113.