Issue: October 2, 2004

Composting leaves sprayed for pests | Bring in amaryllis

Composting leaves sprayed for pests


If I sprayed my trees for aphids this summer, can I compost the leaves when they fall?


It will depend on the insecticide you used and the rate at which you applied it, but most insecticides will have been decomposed considerably in the presence of sunlight. Many of the insecticides will be biologically degraded in the compost pile as the leaves are decomposed. There may be some slight residual, but for most purposes that will not cause a problem.

It is important that the chemicals were used properly and not in too great a concentration so that natural degradation will prevent problems.

If you have aphid problems next year, you may want to try using jets of water to knock the aphids from the portion of the tree accessible to the water from the garden hose. Dislodging the aphids reduces their damage to the tree until they can climb back and resume feeding. In that time, various predators of aphids will make their appearance and often reduce the aphid population to non-damaging levels. Use of the insecticide not only reduces the aphid population temporarily, it also kills the predators who are eating the aphids and other insects. If you can control the aphids in this manner, there will be no chemical residue to concern you in the fallen leaves.

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Bring in amaryllis


Can I leave my amaryllis plants outdoors all winter or should I bring them in?


If you are talking about the typical amaryllis that has large trumpet flowers in late winter, they must be brought indoors. They are in the genus Hippeastrum, formerly called Amaryllis. These are tropical plants and will not tolerate freezing.

There is a plant in the group that remained in the genus Amaryllis, Amaryllis belladonna, which is winter hardy in southern and central New Mexico. It can tolerate some freezing. This amaryllis is the one with large pink trumpet-shaped flowers that flower in late summer or fall when the leaves are dormant. Since they flower when leaves are absent, they are called the "naked lady" amaryllis.

Most people are more familiar with the tropical Hippeastrum, which must be brought indoors before freezing. It flowers in the winter after a period of dormancy when the leaves die back (if you reduce watering). Cool temperatures during this time of dormancy also facilitates flowering. Before leaves reappear, the flower stalk will begin growth that will terminate in large, colorful, trumpet-shaped flowers.

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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, email:, office: 505-865-7340, ext. 113.


For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at, or at the Desert Blooms Facebook.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!