Last weekend, I was talking to the Oregon State University Jackson County Master Gardeners in charge of this year's Winter Dreams/Summer Gardens symposium. When I asked which classes were most popular, it did not surprise me to hear that it was some variation of year-around gardening, especially vegetables.
Interest in backyard gardening has continued to increase, and with our relatively mild Rogue Valley winters, more gardeners are interested in continuing to raise at least some of their produce during this season of colder, shorter days.
Neither my yard space nor my budget has room for a large, heated greenhouse, which would make winter gardening relatively easy. Instead, I use what I call my "hoop house." In there, I can raise many varieties of lettuce that are surprisingly cold-hardy, spinach, kale, chard, bok choy and other greens.
Materials needed for a 4-by-6-foot hoop house in a raised bed are: three 6-foot pieces of half-inch PVC pipe, six pieces of foot-long rebar, of a small enough diameter to fit inside the PVC pipe, a dozen or so paper clamps that open to one inch (get these at an office supply store) and heavy, clear plastic (4 or 6 mil) to cover the structure. If you want a larger hoop house, make adjustments accordingly.
Push the pieces of rebar into the soil on the inside of your raised bed, arranging them so there are three pairs across from one another, with about three feet between the pairs. Leave about 4 inches of the rebar sticking out of the ground. Now arch the PVC pipe over the bed, anchoring it by slipping it over the exposed rebar.
Next, cover the hoops with the clear plastic, anchoring it by using the paper clamps. Be sure to use enough plastic so that the ends of your new greenhouse can be closed. Paper clamps can be used for this, too.
It can get very warm inside this structure when the sun shines, so open the ends to allow air flow as needed. This also helps control fungal problems. If it gets dry, throw the plastic back to let in rain.
Many kinds of seeds for greens can be sown directly in the soil with this kind of protection. Or, if you prefer, start them indoors. Check your seed catalogs for cold-resistant varieties for best results. As you harvest your greens during the winter, throw in a few seeds each time to give yourself a constant supply.
The main drawback of a structure like this is that it isn't enough protection if temperatures drop into the teens, say, for several days. If only one cold night is predicted, I've had success by putting several plastic milk jugs of hot water in the hoop house, as that will keep it above freezing for a while. I know of a gardener who has set several large rocks in his raised bed to act as heat collectors during the day, with the same goal in mind.
The hoop house idea can be used if you want to grow greens in some large pots over the winter. You would need to make a structure to hold up the plastic — perhaps two pieces of smaller diameter PVC in a criss-cross fashion, with ends pushed into the soil on the inside edges of the pot. You could add more protection by throwing a blanket over it on especially cold nights.
Cheers to not only being green, but also to having greens all winter.
Carol Oneal is a past president of the OSU Jackson County Master Gardeners Association. Email her at firstname.lastname@example.org.