1 - Houseplants left outside in freezing weather for a short period of time may survive, but will need special care.

Yard and Garden December 20, 2014

Q.

I take my houseplants outside on sunny days because I do not think they get enough light inside in the winter. However, I think I may have left them outside too long last week. The weather turned cold while I was away and after I brought them inside I noticed that they began dropping leaves for several days. Some leaves turned yellow while others stayed green, but dried out. Have I killed my plants? What can I do to save them?

A.

Different plants have different sensitivities to cold temperatures. Most houseplants are tropical or subtropical plants and cannot tolerate freezing temperatures. Some of these plants may be able to tolerate a brief period of freezing temperatures if the temperature is not too cold. Some house plants are chilling injury sensitive and cannot tolerate temperature below 50 degrees for prolonged periods. So the prognosis for your plants depends on which plants you are growing and the conditions of their exposure to cold temperatures.

You should watch your plants carefully to determine their extent of injury. Some plants may just drop their leaves for a while and then produce new leaves. The tender new growth of some plants may shrivel and die, but older stems may survive with buds to regenerate the growth. Some stems may die to the soil line, but new plants may grow from below the soil line. Some plants may just die.

Because the plants are losing leaves, they will use less water. You should irrigate them with this in mind. Reduce watering, but do not let the roots dry unless the plants are succulent plants that require drying. Overwatering now can encourage growth of disease organisms in the roots. Now is not the time to fertilize. Wait until new growth is apparent before fertilizing. If most of the leaves have fallen, sunlight is less critical until new leaves begin developing. A cool (60 to 70 degree) location will help the plants reestablish. This will reduce drying of the soil and the plant tissues.

Be patient, it may take several months for new growth to appear. I had a similar experience several years ago. I had potted amaryllis (Hippeastrum hybrids) plants and Clivia sp. plants outside for some extra sunlight on a bright November day. I was about one hour late bringing them indoors. The leaves on both plants were frozen stiff. The leaves turned yellow and died on both. The Clivia plants died while the amaryllis bulbs surprised me by producing excellent flowers a few months later. The amaryllis plants (even though tropical or subtropical in origin) benefited from the cold exposure and loss of leaves while the growing points in the Clivia plants were frozen and died. You will probably see similar variation in the responses of your plants.

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: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

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