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A Couple of Cold Nights Coming

PansyThe weather forecasts predict lows in the 20’s coming up.  With the unusually warm weather we have had, plants are more tender and subject to cold damage than they would be in a normal winter. Flowers are likely to freeze, especially on trees like magnolias, which are the plant poster children for freeze damage.  There isn’t much you can do to protect flowering trees.

You can protect flowers on pansies and perennials, and recently planted shrubs—plants that are close to the ground–by placing a blanket over them for the night. The idea is to hold warmth from the soil (the ground is pretty warm) and also to reduce what is called radiation heat loss to a clear sky.  The latter is usually more of a problem on the second night of cold weather, when the wind velocity drops (wind mixes warmer air from near the ground with colder air at plant level) and the sky is clear.

A blanket or newspaper are good insulation; plastic sheeting or a tarp are not; you might put down a layer of newspaper and hold it in place with a tarp. The protection can stay on during the day Saturday, but should be removed Sunday and if the forecast is accurate, you should not need to protect plants on Sunday night.  Remember that anything heavy is likely to damage open flowers, but it’s safer than no cover at all. As far as what I am going to do…probably nothing, since I haven’t planted anything yet this year.  But if I had just planted a budded or blooming pieris or a forsythia, or a hydrangea with leaves showing, I would wrap it in a sheet or light blanket.

Stephanie Fleming was raised at Behnke’s Nurseries in Beltsville. Her Mom, Sonja, was one of Albert & Rose Behnke’s four children. She was weeding from the moment she could walk and hiding as soon as she was old enough to run, so many weeds, so little time. Although she quickly learned how to pull out a perennial and get taken off of weed pulling duty.

This Post Has 5 Comments

  1. Thanks for the suggestion to protect vulnerable plants on the upcoming cold nights. What about spring bulbs, daffodils and such, that are putting up foliage and blossoms? Do they need to be protected?

    1. My experience says, maybe. If it’s just foliage, I would not be concerned. If it’s actually flowering, then I believe that the flower will come through it, but that the stem will be weakened, and come around Monday or Tuesday, some of them will be unable to support the flower and will be bent over.

      Larry Hurley

  2. With cold rain Friday night, I’m going to use an over-turned plastic trash can for protection. Do I need to also cover with sheets/blankets underneath the trash can?

    1. Trash can should work well, with a lot of trapped air. If you can uncover it during the day, if above freezing, that wouldn’t hurt. Better air circulation, reducing possibility of disease. I believe that anything that came through last weekend should be good through this coming cold snap. It seems like it won’t be as cold, even though there will be more cold nights. Also, the mostly cooler weather has slowed growth down some, and I don’t think plants are as tender as they were going into last weekend. At my place, established hellebores had no damage last weekend (March 3-5, 2017), even though in full bloom, for example, while the magnolia flowers that were open burned as expected.

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