Unwelcome cold snaps present quandary

by How Does Your Garden Grow? By Sharon Daniels

Daffodils, quince and forsythia are blooming or in bud in the area this week. Because they are opening earlier than in many years, we are prone to worry that frigid temperatures or heavy snows could wipe out the flowers we so anticipate in spring.

However, when unseasonable warm temperatures prod plants to respond unseasonably and break dormancy, there are ways to protect spring-blooming plants.

Spring-flowering bulbs seldom are permanently damaged by heavy frosts, extreme cold or heavy snow, but if they already are in bloom, their stems may not hold them up and spring bouquets will suffer.

Lightweight row covers, old blankets, sheets of plastic and large cardboard boxes can help tender plants retain warmth from the ground. Frost is most prevalent on a still night, so there should not be a need to anchor covers to prevent them from being blown off.

If you use clear or black plastic, it is critical that you remove it as soon as possible after next day's sunrise, to prevent over-heating.

For a garden planted with early vegetables, pile straw mulch lightly over tender plants, and remove it when temperatures moderate.

If a cold snap is predicted, you may try to save plants by simply watering them thoroughly.

Another way to protect plants from frost is to spray water which will turn to ice and produce a small amount of heat. Heat gets released when water begins to freeze.

If you mulched plants last fall, leave it on perennials as long as possible. It keeps soil cooler and helps prevent plants from breaking dormancy too early. When plants start to grow, pull mulch away from crowns but keep it close in case they need protection if a hard freeze is possible.

A light freeze, 29-32 degrees F, will kill some annuals and vegetables and cause cosmetic injury on hardier plants. A moderate freeze, 25-28 degrees F, will kill hardier annuals and vegetables; leaves of some perennials and deciduous shrubs may get mushy and drop. A hard freeze, 24 F and below, kills annuals and vegetables, extensively damages perennial foliage, and may cause loss of tree or shrub leaves and flowers.

Spring-flowering bulbs withstand a certain amount of frigid temperatures but will collapse in a hard freeze. They should be fine for next year but it is critical that you let foliage remain on plants until it completely browns. This is their process to store the energy required to produce future flowers.

Sharon Daniels is a Virginia Cooperative Extension Master Gardener volunteer.