Released Jan. 22, 2008
BOZEMAN, Mont. -- Have you noticed the days getting subtly longer? Many of our landscape plants have had their chilling requirement fulfilled and are waiting for spring. At this time, it is possible for them to awaken in response to warm temperatures and once again become vulnerable.
Temperature fluctuations and thaws are particularly difficult for plants at this time of year. Just how warm the temperatures must be for our plants to respond depends on the species, but 27 degrees is a good ballpark temperature to remember. If temperatures become mild for several days, followed by subzero temperatures, you can expect some winter damage symptoms come spring.
If grafted plants such as roses and fruit trees awaken, they may die above the graft union. If this occurs, it's best to replace the plant. Root stock of grafted plants, when allowed to grow, usually produces unacceptable fruit and flowers.
Winter scorch is also commonly seen this time of year on conifers. Needles on the south and west sides of the trees turn reddish brown. This is not to be confused with the reddish winter hue of some junipers, which is normal. In an area with good snow cover, sun and reflected sun dry out the needles. Since the soil is frozen, the roots can't absorb water to replace the moisture that has been lost. Strong winds in an area can worsen winter scorch on conifers. So the combination of intense, reflected sunlight and prevailing westerly winds results in reddish needles on the south and west sides of conifers.
The big question is, "Will my plants die if they are showing these symptoms?" Unfortunately, we have to adopt a wait and see attitude until spring. For now, feel the needles. If they are brittle and break easily in your hand, it's likely they are dead and at least that branch probably won't make it through the winter. However, if they're brown but flexible, they just may green back up in spring and survive. The tree, however, will be stressed. The discoloration that is showing up now is from damage that occurred some time ago, and additional damage might show up as the season progresses.
To reduce further damage, water your conifers any time the soil is not frozen. This helps to fill the soil pores with water reserves that will help get your plant off to a good start in spring.
Even though it's tempting, do not cut out limbs you're not sure are dead until about the Fourth of July. They may not be dead, and may take longer in the spring to green up due to the stress they've been under. Be sure to water your plants well in spring and summer, and next fall, remember to water deeply prior to the ground freezing.
Hopefully you gave your deciduous trees a good drink of water after their leaves fell and before the ground froze. Since they aren't active through winter as conifers are, they won't benefit as much from additional water in a midwinter thaw.
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http://www.montana.edu/cpa/news/nwview.php?article=5519
Contact: Cheryl Moore-Gough (406) 994-6523 or hort@montana.edu
