Properly applied frost cloth can protect your frost sensitive plants from the cold even when the temps dip into the 20s!
So with plants that are close to the ground you can protect them from a frost, or even a freeze if you cover them up. You can use plastic, newspaper, bed sheets, plastic tarps, anything you can find. But the thicker, more insulated the covering you use, the more protection you are providing for your plants.
Properly applied frost cloth can protect your frost-sensitive plants from the cold even when the temps dip into the 20s (°F). We recommend frost protection when temperatures hit the mid-to upper-30s (°F).
It is important that the frost blanket is large enough to cover all the way to the ground. This helps retain the heat from the soil which will keep your plants on average 5-10 degrees warmer.
Frost cloth is designed to allow sunlight, air, and moisture to pass through while trapping heat around the plant, creating a microclimate that provides frost protection, protecting plants from the cold.
Properly applied frost cloth can protect your frost sensitive plants from the cold even when the temps dip into the 20s! If necessary, the frost cloth can be left on the plants for an extended period of time without the risk of harming your plants.
Unlike plastic, fabric traps some air in the woven material, so leaves that touch a fabric cover are better insulated and not as likely to get freeze damaged (unless the fabric is saturated with water).
Large blankets or bedsheets can be used as frost cloth substitutes, but whether you are using actual frost cloth, or something pulled from the linen closet, it is very important to use it correctly to be effective. The cloth must touch the ground at all points, as it works by trapping heat that radiates from the soil.
Will a covered porch protect plants from frost? Yes, it will provide partial protection from light ice and chilly winds. Uproot tender perennials — Tender perennials are plants that cannot withstand deep freeze (roots, bulbs, tubers, and corms).
Frost blankets, also known as row covers, are made from lightweight, non-woven materials designed to trap heat and moisture. They provide a high level of insulation while allowing light and air to pass through. Landscape fabric, however, is heavier and primarily designed to block sunlight and suppress weeds.
If using a good covering and the temperatures are expected to remain low, you can keep your plants covered for days.
Unlike farm grade plastic, frost cloths are permeable and allow air, water and sunlight to pass through. However, keep in mind that the heavier the fabric, the less permeable it is. For example, a 1.06 oz frost cloth will allow 75% of light to pass through.
Plastic that touches your plants can often be even worse than no protection since it can hold moisture against plant tissues and cause more serious freeze damage.
Properly used, frost blankets will not suffocate plants. They're designed to allow air and moisture to reach the plants while protecting them from cold temperatures. However, they should not be wrapped too tightly around the plant, which could cause damage.
Covering plant material at temperatures between 39-30 with freeze cloth or covering can be effective. Prolonged exposure at temperatures of 28 degrees and below will notice protection results diminish with each degree dropped.
Fiberglass consists of extremely fine glass fibers and is one of the most ubiquitous insulation materials. It's commonly used in many different forms of insulation: blanket (batts and rolls), loose-fill, and is also available as rigid boards and duct insulation.
Food grade materials, such as aluminum foil, heavy freezer-weight plastic bags, heavy plastic wrap and parchment or freezer paper are excellent choices. It is safe to freeze meat or poultry directly in its supermarket wrapping, but this type of wrap is thin and lets air in.
Good insulators are materials that do not conduct or transfer energy well and keep your ice from melting. Things like polystyrene, bubble wrap and cotton wool are good insulators.
Plus, unlike plastics and bed sheets, these fabrics allow air and moisture to percolate down to the ground around the plants. And temperatures don't have to be freezing or below to benefit from the use of frost blankets.
It's also important to note that frost cloth is not a permanent solution and should be removed during the day when temperatures rise above freezing to allow sunlight and air to reach the plants.
Place cardboard boxes, large trash cans, or plastic tubs over outdoor plants. Be sure to cover the plants all the way to the ground. The warmth from the soil is what keeps the plant warm, since the soil takes longer to freeze.
Plastic tarps will transmit cold air to the plants, causing more harm than good. Use cotton blankets or frost cloths for better protection.
Despite its convenience, there's one item you should stay away from to cover your plants. If you're looking for tips for protecting your plants from frost, avoid using garbage bags as plant covers. Trash bags are not the best protection against frost damage, primarily due to their material.
Some of these products will claim to protect down to minus 6°, but it's advisable not to rely on that info if plants are vulnerable. A more realistic expectation is that 25-30 gsm will protect down to minus 3, while lightweight horticultural fleece should protect plants when temperatures are just below freezing.