The University of Minnesota is warning about the frost to come.
They say, “The early warm-up this spring, and extra time at home, have gotten people out in their gardens earlier this year. This weekend’s weather, for many parts of Minnesota, is not great news for those who have already planted their tender annuals. With temperature predictions ranging from upper twenties to lower thirties, many of those plants could be at risk. Here are strategies for coping with late frosts.”
Here is what to know;
Be aware of the weather and take precautions early. Clear skies, a lack of wind and a chilly afternoon generally precede a night with a drastic drop in air temperature.
Protect your plants:
If a light frost is predicted, drape tender plants, newly planted perennials and anything with sensitive new growth or flower buds with old bed sheets. If a killing frost is predicted, prop the sheets up on stakes so that they don’t touch the foliage, and pin down their edges with stones or bricks. The sheets trap warm air, preventing it from radiating into the atmosphere.
As an alternative to sheets, some gardeners run a sprinkler over the plantings through the night when a light frost is predicted. This sometimes works, sometimes doesn’t . . . but will certainly affect your water bill, and may be considered a waste of water.
Move container plantings to a sheltered but unheated location, such as on a porch or into a garage or shed.
If you wake to find tender plants covered in frost, try spraying them with water to wash the ice crystals away. If the sun melts the crystals before you have a chance to, irreversible tissue damage will be done. The plant may survive, but it will have scars. Annuals will likely die, except for the hardiest annuals.
If potted plants have been left out and are affected by frost, don’t try to warm them by bringing them indoors; the sudden change in temperature would damage them further.
What if it snows?
Snow collecting on a plant surface will not directly harm the plant structure, in fact, the snow may help to insulate the plant from even colder air temperatures, keeping the temperature on and around the plant near 32˚F.