How to Use a Frost Blanket to Harden Off Seedlings

Know what weather conditions to expect in your area and the hardiness of the plants you are attempting to grow. Whether you are purchasing annual vegetable and flower plants or starting them from seed in hot beds or a home greenhouse, you need to protect the plants from a killing frost while allowing them to "harden" to outside weather conditions. To accomplish this, you need to monitor local weather forecasts and know the tolerances of the plants you are attempting to grow.

Use frost blankets to protect the seedlings from overnight killing frosts. Uncover the seedlings and place them in a sunny spot, if possible, during the day if the temperatures allow. Frost blankets are commercially available fabric plant covers and come in a variety of sizes. Gardeners can also use burlap or other cloth materials for covering plants. Plastic coverings are not suggested as they allow too much of the warmth in the soil to escape. Watering the plants before covering helps bring soil warmth to the surface and keep the plants above freezing temperatures under the frost blanket.

The plant hardening process should last one to two weeks.

Leave the seedlings uncovered during nights when frost is not forecast, as the spring progresses. This helps acclimatize the plants to normal, outdoor weather. Other suggestions include watering only when the soil around the plant is dry and exposing the seedling to the wind.

Transplant the plant into the garden when the last chance of frost has passed in the spring or early summer.