Issue: September 22nd, 1997

Pests and diseases from outside


When I bring my houseplants indoors from their summer outside, how can I be certain that I am not bringing insects and diseases indoors?


While you can never be certain you are not bringing problems indoors with your plants, you can reduce the likelihood of problems by carefully inspecting your plants and discarding those which have evidence of disease. If insects are observed on the plant, it is important to identify the insect to determine if it will be harmful to the plant on which you found it or harmful to any other houseplants. Since most people don't want insects inside, you may then treat to eliminate those which are harmful and wash or pick the benign and beneficial insects from the plants. Insect and disease problems are more difficult to manage indoors, so failure to inspect carefully before bringing them indoors can cause major problems later.

Even after the best inspection, you may later find that insect and disease problems develop. There are insecticidal soaps and oils which may be used indoors, but they may damage wood work, furnishings and curtains, so be sure to protect them from the spray. You may move some plants into the shower or bath area to treat them. Let the plants dry well before moving them back to their indoor growing location. By applying the treatments in the bath, your furnishings can be protected and the overspray can be washed away following treatment. Be sure the residue is washed well away to avoid injury to yourself or family slipping in the bath. Do not use materials inside that are toxic to your family, not even in the bath. If insecticides other than insecticidal soaps and oils must be used, or if fungicides must be applied, wait for a warm day when you can take the plants outside to be treated. Again, wait until they have dried before returning them to their indoor location.

If the weather will not allow treatment for several days or weeks, isolate the affected plants in a separate room, or by keeping them as far as possible from the other plants until treatment is possible. When caring for your plants, always care for the non-quarantined plants first. This will avoid carrying problems from the quarantined plants to your healthy plants on your hands or clothing.

Blooming amaryllis


I have an amaryllis which bloomed in December, and since then has not produced a flower, only green leaves. When is the best time to force it to bloom, and how do I do it?


Amaryllis bloom once each year. They need a dry, cool period to induce flowering and will therefore tend to bloom in the winter. They are native to tropical climates and do not tolerate freezing.

To force flowering, reduce the water supplied to the plant in the autumn. Don't let the bulb dry completely, but let the soil dry between waterings. Don't just wait for the soil surface to dry, but let the all the soil in the pot dry. The pot will become considerably lighter, a way you can measure how dry the soil has become. Some soils are difficult to re-moisten once they have become dry, so it may be necessary to place the pot in a dish pan or bucket filled with water almost to the top of the pot. Be careful that the pot does not tip over as it may tend to float. Once it has absorbed water through the hole in the bottom of the the soil has become moistened, lift the pot from the water and place it where the excess water can drain. Never let the pot sit for prolonged times with water above the bottom of the pot, but for brief periods it is ok to allow the water to rehydrate the soil.

Place the amaryllis in a cool place where it will receive the necessary cool night conditions. Temperatures as low as 50 degrees Fahrenheit, or briefly lower, will not harm the plant. However, freezing temperatures should be avoided. Several weeks of this cooling treatment will be needed to induce flowering.

If the plant was kept in location that was too shady during the summer, it may still not be able to flower. It must store sufficient quantities of carbohydrates to enlarge the bulb before it can produce flowers. Be sure the summer location provides bright, not direct sunlight for at least four to six hours each day. I grow my amaryllis in pots outside in the shade of an apple tree during the summer. They receive a few hours of direct sunlight in the early morning. I leave them outside until just before frost is protected. If the weather becomes unstable, where frost is possible, I move them near the house under the eaves where they will be protected from light frost. When the danger of freezing in imminent, I bring the plants indoors into the room which will be their home until danger of frost has passed the next spring.

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!