Water Plants in Winter to Reduce Freeze Injury

Date: Nov. 13, 1997
Editor: D'Lyn Ford,  (505) 646-6528, dlford@nmsu.edu

LAS CRUCES -- New Mexico's desert is a land of temperature extremes. With the onset of cooler weather, warm days and cool nights can cause freeze injury to landscape trees, shrubs and roses.

Dormant trees can withstand freezing winter temperatures, said a New Mexico State University plant pathologist. But freeze injury commonly occurs with unexpected drops in temperature during the early fall before dormancy or in early spring when the trees start growing again.

"Spring freeze injury is more common in New Mexico," said Natalie Goldberg, with NMSU's Cooperative Extension Service. "Injury typically occurs on the southwestern side of a tree or shrub -- the side most exposed to the sun."

As temperatures rise in the spring, plants begin to grow. A cold snap of freezing temperatures can cause injury that may take a year to become visible.

"The injured part of the plant is affected directly by the freeze and indirectly by becoming more attractive to insect and disease invasion," Goldberg said.

Native desert plants such as sage, juniper, cedar and pine are more tolerant of cooler temperatures, she said. Plants that are less cold hardy include roses, bougainvillea, oleander, photinia and euonymus.

To protect landscape trees and shrubs from freeze injury, Goldberg suggests watering the plants throughout the winter. "We've found that trees and shrubs will have some cold hardiness, if they're watered once a month throughout the winter season," she said. "This keeps the temperatures up a bit in the area around the plants."

Other ways to protect trees and shrubs from freeze injury include painting tree trunks with white latex paint or covering the plants with protective material.

"A sheet or bedspread can protect plants from freezing night temperatures," Goldberg said. "But be sure to remove the covering in the morning, so the plants don't get too hot during the day."

Water, paint and sheets may only protect for an additional degree or two, but that may be enough to help plants survive New Mexico's fluctuating temperatures, she said.