Raised garden beds provide good air circulation for plants, and have many other benefits as well. But if you want to grow a winter vegetable garden in northern climes, you’ll need to protect plants from frost and snow.
Fortunately, it’s easy to make a covered support by building a framework of hoops and covering it with a material that will shield your plants from cold.
Start by placing lengths of 1-inch PVC pipe long enough to reach from the bottom of your raised bed or planter to the top of the soil or even a couple of inches below.
Then simply bend pieces of ½-inch PVC pipe long enough to form semi-circles at the desired height and slip their ends into the 1-inch pipes inside the bed.
Cover the hoops with floating row cover material or poly film such as spunbonded polyester or polypropylene, both of which are extremely lightweight and can protect plants from frosts down to about 26 degrees Fahrenheit. Or use heavy-duty poly film, such as polyethylene, polycarbonate, or polyvinyl chloride, will turn your raised beds into mini greenhouses and protect against cold temperatures as low as 22 degrees.
Poly film comes in thicknesses up to 24 mils. A higher the number of mils offers more protection from weather but also reduces the amount of sun and light that can get to your plants.
Be sure to get poly with UV light inhibitors because it lasts longer than untreated film. Should your film suffer a rip or puncture, simply repair with clear poly film repair tape.
Remember that poly film can trap heat when temperatures start to rise, so remove it when all danger of frost is past, or buy vented film.