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Spring and Autumn Frost Protection
When Vegetable Plants Need Cold Protection
During the beginning and end of the garden season, the plants in your home vegetable garden experience cool nights and warm days, some with frost or even light freezing conditions.
These are periods of cold slow growth, slowing flower production, and delayed ripening. Cold nights even kills many warm-season and tropical vegetable plants. In this section, learn to protect your plants during seasonally cold weather, including:
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- Recognizing temperatures that affect or kill plants.
- Understanding frost-protection measures for plants in home vegetable gardens.
- Learning plant care requirements for warm days and cool or cold nights.
- Discovering what coverings and protection to provide plants during cold weather.
- Placing mulch and landscape fabric on soils to help trap warmth.
- Knowing the details of season extending to prolong harvests from your garden.
- Providing other care and fertilizing to help plants through cold weather.
Spring and Autumn Cold
Both spring and autumn weather are times filled with uncertainty in a vegetable garden.
During these seasons warm, balmy days intermingle with periods of rain and hail, wind, cold, or even frost. In spring in many areas, frosts occur even weeks into the gardening season. Similarly, as days shorten and autumn chills begin, your tender vegetable plants may need frost protection.
In either case, protect your plantings whenever conditions turn unpredictable. Three easy practices can help your plants survive cold weather: covering, mulching and other special care.
Temporary Covers
Gardeners have long extended their growing seasons into early spring and late autumn by using crop covers, covering plants with frost-protection cloth, and insulating soils with mulch.
Such measures may add 1–2 months or more to the growing, fruiting, and ripening time vegetables have to produce in your garden. In milder climates, frost protection measures allow year-round gardens.
Hot Caps and Covers
Coverings made of translucent waxed paper, plastic, glass, or non-woven fabric insulate tender seedlings by isolating the air around them and preventing cold dew from forming on their foliage.
Sunlight passing through the covers, while necessary to keep photosynthesis active, has an added benefit of warming the soil and air within the covering. Such coverings also help keep humidity levels high and reduce the need to water.
Take care, however, on too-warm, sunny days; remove or partially lift your plant coverings to allow some solar heat to escape or tender shoots on your plants could be damaged. Remove the coverings entirely when the plants have become hardened and the hazard of frost has passed completely.
Protecting Plants from Frost
For larger plants floating row covers are the solution to late-season frost protection, lightly covering and insulating plants beneath and blocking dew or frost but allowing moisture from the plants to evaporate and pass through without condensation.
Remove the floating row covers during the days and cover the plants at evening when threat of frost exists.
Applying Insulating Mulch
Used either alone or in conjunction with coverings, mulching around young plants helps them make the transition and protects them from cold snaps.
Mulch conserves soil moisture. It insulates plants and slows soil-temperature fluctuations and prevent weed seed from germinating by blocking their seeds from light. Organic mulches such as straw, compost, or wood chips—lightly fertilize your plants as they decompose.
Some gardeners cover their planting beds with so-called “weed block” landscape fabric made of non-woven natural fibers, then plant through it [see Transplanting Through Weed-Barrier Fabric for more information about using that approach].
Black mulch cloth traps the heat in sunlight to warm soils faster in spring and keep them warm in autumn. Warm soils help plants survive cold temperatures.
Because mulch provides benefits beyond its neat and aesthetic appeal, always consider applying it around your vegetables after planting. A layer of mulch, 1–2 in. (25–50 mm) thick, usually is adequate for young vegetable plants. Keep the mulch away from the plant stems, however, as it might trap moisture and encourage fungal diseases or hide rasping insects that would eat your young plants.
Other Care Practices
Always keep your new seedlings evenly moist until their roots have become established, and remember that watering in mid-afternoon on sunny days before cool nights helps the soil retain its warmth long into evening.
If humidity is low, occasionally mist your seedlings or established plants’ foliage to keep them well hydrated.
Strong plants survive cold easier than those that are weak. Apply foliar fertilizer—water-soluble nutrients absorbed by the leaves and stems of the plant—with irrigation water to give new transplants and established plants a boost.
A feeding mixed at half the strength advised on the package directions and applied every other watering for the first 3 weeks will ensure that your plants get a strong, vigorous start. Once they are established, apply water to them beneath their foliage.