Plants need fresh air and good air circulation. This is true even in winter. No matter what form of protection you use for your plants, you’ll still need to insure they get enough ventilation.
Fortunately your plants can survive short periods of being “closed up” when weather makes it impossible to do otherwise.
When Lettuce Needs Protection
When temperatures are forecast for 29ºF or below I cover my fall/winter lettuce beds.
Although lettuce can survive 28ºF , I’ve found the forecast is never exact.
Temperatures can easily slide to 27º when 28º or 29º was forecast. Below 28º without protection and you’ll most likely lose your lettuce.
(My) First Step to Get Air Circulating After a Cold Spell
One year was unusually cold with lots of ice and snow. Beds remained covered and “closed” for more than two weeks. At the first opportunity I broke up the ice around the ends of the beds and opened each end of my low tunnels to let fresh air circulate.
If night time temperatures were expected to fall below 30º or so, I closed the ends again.
Your first step after a cold spell will depend on what type of system you have.
Reason Plants Need Air
- They need air to synthesize their food from carbon dioxide (from the air) and water (from the soil).
Reasons for Good Air Circulation
- Prevents heat from building up under plastic coverings. This can happen even on cold days when the sun is bright.
- Allows evaporation of excess moisture.
- Keeps plants strong and rigid.
These things help prevent plant diseases and various pests that would otherwise thrive.
Uncover When Weather Permits
A bright sunny day with light winds and temperatures of 39º might feel too cold to you, but your plants will love it. It’ll help keep them strong and healthy.
Rain – Another Benefit of Uncovering Your Beds
Plants need the rain in winter as well as summer.
If for some reason your soil becomes dry and temperatures drop below freezing, it can kill your plants even if they’re under protection. To withstand the cold, plants need sufficient moisture. (Not soggy soil, but not totally dry either.)
As I mentioned in the post on Watering Guidelines “Don’t go by the top of the soil being dry. Push your finger into the soil. If it’s moist 1 1/2 to 2 inches down — don’t water.”
In case you’ve not experienced this:
With temperatures at 32º, freezing rain, and their leaves encased with ice, most lettuces remain unscathed when temperatures rise again. (I’ve had this happen many times.)
Common sense will prevail here. If you have any doubt about what the temperatures will be, cover the beds again. Better safe than sorry.
If you have a system that’s easy to handle like mine, it’ll be easy to pull the plastic over the beds when unfavorable conditions are forecast.
Nature’s perfect covering for cold hardy plants is snow. It protects and still allows for needed air.
So if you get an unexpected snow that covers your lettuce (and temperatures are between 30º and 32º or warmer), it should be just fine. You can cover the beds again and not bother about the snow on the lettuce.
Man-made protection for plants is not as accommodating as nature’s, but with a little thought and effort we can make it work.
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