Cold Injury Above Freezing

Question:

Will a temperature of 33 degrees Fahrenheit hurt any type of common houseplant or outside plants?

Answer:

The answer is yes! Many plants can withstand temperatures below freezing, many can tolerate temperatures near freezing, but some cannot tolerate low temperatures even when the temperature is above freezing. The time the plant must endure the cold temperature is also a consideration. Longer durations at a low temperature will result in more injury.

Many houseplants are from the tropics and very sensitive to low temperatures. As a student, I grew a plant called flame violet (Episcia) that died each year just after the Christmas vacation. When I went to my parents' home during the Christmas holidays, I set the thermostat at 50 degrees in my apartment. Later, after several dead plants, I realized that the low temperature killed my flame violet. By keeping the temperature near 60 degrees, subsequent flame violet plants survived without injury. I believe this is one of the most sensitive plants to "chilling injury", but there are many others, including common garden annual vegetables and flowers, which will also exhibit injury at low temperatures above freezing.

I must also ask how you are measuring the temperature. Temperatures measured in one location may vary by several degrees from temperatures in a nearby location. Low temperatures reported by the news or weather service may vary considerably from the temperatures in your garden. If you measured a temperature of 33 degrees or heard it reported on the news, it is very likely that temperatures below freezing existed somewhere in your landscape. If your question is based on the observation of frost damage when your thermometer said it didn't freeze, this is probably the explanation.

Germinating Virginia Creeper Seeds

Question:

How does a person germinate seed for a Virginia creeper vine?

Answer:

Seed of the Virginia creeper may be germinated by planting them in the fall or by "stratifying" them in moist vermiculite or peatmoss for eight weeks in a refrigerator at 40 degrees before planting them outdoors or in pots. The required cold exposure is usually provided by the winter temperatures if the seed are planted outdoors, but you can speed germination by storing them in moist vermiculite or peatmoss in the refrigerator for a while before planting. They may be kept in plastic bags, or any other sealed containers, so that they do not dry while in the refrigerator.

This "stratification" treatment is standard practice for seeds of plants from temperate climates. Under natural conditions, they must overwinter before they will germinate. We must provide conditions to simulate winter conditions before they will germinate. Tropical plants, on the other hand, do not have this requirement for germination.

Please join us on Southwest Yard & Garden, a weekly garden program made for gardeners in the Southwest on: KNME-TV Albuquerque at 1 p.m. Sundays, KENW-TV Portales at 10 a.m. Saturdays, and KRWG-TV Las Cruces at 10:30 a.m. Saturdays (repeated at 11 p.m. Sundays and 1 p.m. Thursdays.)

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.

Links:

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 desertblooms@nmsu.edu, or at the Desert Blooms Facebook page.

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