Whether commercial or homemade, these plant cover-ups are
The goal is to trap the sun's heat during the day, but within reason. On a sunny winter day, temperatures inside an airtight cold frame or other season-extending device can quickly climb above 100 degrees. Excessive heat can be kept in check by venting your setup. Close the vents by late afternoon to keep that heat gain
Season extenders don't only help protect plants from cold temperatures and frost. They can also be used to start seeds, harden off plants, warm up the soil, grow cool-weather crops, and speed up fruit production. Extend the harvest of lettuce and other heat-sensitive veggies and flowers by protecting beds with a portable frame covered with lath strips or shade netting. And the insulating qualities of a cold frame or hoop tunnel can keep your fall veggies producing long past what Mother Nature would normally allow.
Don't let the weather catch you by surprise. Choose one of the season-extending techniques that follow and protect your plants regardless of what the weather doles out.
Floating row covers
Made of spun polyester, polyethylene or polypropylene, these fabric-type covers vary in weight, thickness and degree of protection. They are also permeable to light, water and air. Some allow 50 percent light transmission and protect plants down to 24 degrees, while others allow up to 90 percent light transmission with frost protection down to 27 degrees. But they are all easy to use and help gardeners extend the growing season on both ends.
varying degrees, floating row covers protect tender seedlings and plants
from damage caused by wind, rain and pest insects. Depending on the
fabric's weight, these covers can be laid loosely to "float" over seeded
beds and plants, or they can be supported by stakes or hoops. The key
is to keep the row cover on seedlings for several weeks. Just be sure to
bury the cover's edges so the wind doesn't blow it away.
Cloches and hoop tunnels
Designed to protect plant beds and garden rows from single to wide, these simple, somewhat portable, tent- or tunnel-like devices provide an inexpensive alternative to a greenhouse. You can make them any height, from low to the ground on up.
Frames can be fashioned from wood, plastic or metal. Simple frames can be made with bendable PVC pipe ( 1/2 or 3/4 inch) or black poly pipe to form a series of semicircles spaced 5 to 10 feet apart. An added length of pipe secured to hoops on the top centerline will give your structure added strength and support. Secure the ends by sliding the pipe onto in-ground rebar or metal rods, or fasten to metal fasteners (pipe clamps) attached to the sides of the raised bed.
A variety of
materials can be used to cover frames: plastic sheeting or greenhouse
plastic, a row cover, or even shade cloth or bird netting. Garden clip
fasteners work well for securing the covering to frames made from pipe
or PVC. Ideally the system should be designed so that ends can be easily
opened during the day to vent and closed completely at night to retain
any heat gain.
Spring-sown seeds germinate slowly in the soil and seedlings are sluggish because of chilly rains and even colder nights. Plastic mulch helps warm the soil and speed germination. As soil cools down in fall, plastic mulch can hasten ripening of summer veggies like tomatoes and peppers.
There are a wide variety of plastics to choose from, with some warming the soil more than others. Depending on the color, plastic mulch can reflect, absorb or transmit sunlight. But almost all types reduce surface evaporation and suppress weeds.
Basic black plastic can warm soil temperatures from 5 to 7 degrees to a depth of 2 inches below the soil surface. Clear plastic heats up soil temperatures even more -- up to 14 degrees -- but its transparency does allow weeds to grow beneath it. Green plastic is just as effective at warming the soil as clear mulch, but without the weed growth. Brown plastic warms the soil better than black and is a more effective weed deterrent than green plastic. For maximum solar gain and weed control, infrared-transmitting mulch (IRT) combines the best of both clear plastic and black plastic.
Regardless of the color, successful soil warming or cooling depends on how you install the plastic. Before laying the sheeting, install soaker hoses or a drip irrigation system in the bed. Stretch the plastic tightly over soil surface to ensure good contact, then bury the edges so the plastic stays in place. Use scissors or a sharp knife to cut holes for planting.
These bottomless boxes provide a favorable greenhouse environment for extending your growing season. Their popularity stems from their three-season appeal.
In spring they are used to germinate seeds, grow and harden off transplants, and raise compact cool-season veggies to full size weeks before the first frost. Fall and winter uses are not limited to growing cool-weather crops well past a hard frost. Gardeners also use them to store root vegetables and to chill bulbs for forcing.
The base can be made of wood, brick, concrete blocks, straw bales, or a wood frame fitted with polycarbonate panels or foam insulating board. Top the base with a hinged transparent lid, typically framed in wood. Glass works well but is heavy and can break. Lightweight options include Plexiglas, polyethylene film or a double layer of clear plastic sheeting. Be sure to prop the lid open on sunny days, or install an automatic frame opener to help regulate the inside temperature.
Ideally, you should locate the box with the lid slanted toward a southern or southeastern exposure. That can be accomplished one of two ways: cutting the sides of the box frame at an angle, or sinking the frame into the ground at a slant.
Reduce your heat loss in winter by covering the lid with a blanket on cold nights and/or lining the inside with insulation board. Or turn up the heat by converting your cold frame into a "hotbed" by replacing some of the soil inside the frame with about 4 inches of fresh manure, topped with several inches of soil. The manure will produce added heat as it decomposes.
Individual plant protectors
When you have only a few vulnerable plants to protect from an unseasonable frost, the simplest cover-up can often be found inside your own home, such as an old sheet or blanket, piece of burlap, bottomless cardboard box, coffee can with both ends removed, or the handy plastic gallon milk jug with the bottom cut out. All are simple, no-cost ways to provide some degree of on-the-spot protection.
Commercial hot caps work well during sunny days and clear nights. These individual plant covers function as miniature greenhouses by trapping heat from the sun. Designs vary from wax-paper cones to water-filled plastic tepees, such as Wall o' Water and Kozy-Coats. They work well to speed germination and plant growth, and to protect young seedlings from cold nighttime temperatures or when frost is in the forecast.
-- Garden writer Kris Wetherbee is the author of "Attracting Birds, Butterflies & Other Winged Wonders to Your Backyard."