Tuesday, January 9, 2018

FAQ: Should I cover my plants during cold weather with a plastic sheet?

Q. Should I cover my plants during cold weather with a plastic sheet? It's getting unusually cold tonight here in Atlanta, so I covered my patio plants. Here's a picture. Is this good enough?

A. I doubt it. There are better coverings to use. Plastic sheeting has no appreciable insulation value itself. Plants that come into direct contact with it will be damaged by the cold, so it's important to keep the plastic from touching them by using some sort of supporting structure. To keep the plastic from collapsing onto the plants due to the weight of precipitation, the supports should keep the plastic taut allowing water or snow to slide off.

Another problem with plastic is that it doesn't breath, so heat and condensation can build up beneath it. Even on cold days, the heat of the sun can cook your plants.

If you're caught off-guard by cold weather, a cotton sheet or lightweight blanket would be better for covering. The fabric would allow some air exchange to avoid heat build-up, but still provide insulation. Again, if precipitation is expected, provide support. Soggy blankets are heavy!

You should plan ahead and buy some material manufactured for the plant nursery industry. One vendor offers a thermal blanket made of a "white, non-woven, needle punched polypropylene material." It's designed to "allow rain and irrigation through ... while holding in precious heat."

The same advertises a "1.5 oz. fabric [which] is ideal for protecting flowering annuals, bedding plants and vegetables from severe cold and freezing. Temperatures underneath the fabric are 6 to 8° warmer than outside conditions...".

You should be able to find products like these at an independent garden center or by mail-order.

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