Considering Season Extension

Written By: Carrie Caselton Lowe The seed catalogs are trickling in and visions of this year’s gardens are taking shape. Even with a mild autumn like we had last year, it’s always the case that most gardeners want crops to last a little longer than Mother Nature allows. This year was basil for me. The earliest frost killed our basil too soon. We don't have a lot of season extension at Glacial Hills Community Farm, so when the cold frost settles, which happens earlier in the hills than other areas, much of our warm weather crops are done.

At our small scale farm, we don’t use any serious season extension with permanent structures because, frankly, farming in winter is cold and cleaning vegetables in winter is no fun. We do, however, use simple, inexpensive season extension techniques because a little layer of insulation for the vegetables makes a major difference. But there are other benefits. Low tunnels are quite easy and inexpensive to set up. Whether using fabric row cover or plastic, the material can be supported over the crops by using hoops of heavy gauge wire (9 gauge works well) or PVC. The length of the hoops depends on the width of your garden beds. A call to your local garden center will tell you what’s available locally. Otherwise, a quick internet search for row cover, garden fabric, or low tunnel plastic offers a lot of information as well.

The influences of season extension are many. Sure enough, the crops are insulated from the cold on both ends of the season, but they are also protected from many pests. Any cabbage family crop does well when started under a low tunnel, which protects from the onslaught of spring flea beetles and cabbage moth caterpillars. The row cover can be removed once the tender seedlings are old enough to handle a few cabbage moths and the flea beetles have flown the coop, so to speak. Another benefit of using plastic is for crops that don’t like as much water as we sometimes get, namely tomatoes. Tomatoes grow best with a consistent volume of water over time. Tomato diseases spread easily when tomato leaves get wet, and the fruits split during large rain events. So tomatoes grown under plastic (with good ventilation) can allow for even water distribution with the use of irrigation and prevent disease. BUT pollination can be inhibited by covering tomatoes; it doesn’t stop fruit production, but it decreases yield. So plant a lot of pollinator friendly plants next to your tomato tunnels when covering them.

Low tunnels won’t work for crops like tomatoes, so for larger vegetables you will need to install a higher tunnel. Of course there are the large, permanent hoop houses that most of our local vegetable farmers use, but there are also smaller, temporary structures that you can build called caterpillar tunnels. My husband and I have built one of these. For about $200, we built a caterpillar tunnel with a 75’ by 50’ foot piece of plastic, 10 - 20’x1” PVC hoops, 20 pieces of 3’ rebar hammered into the ground for stakes, and a whole lot of bailing twine. Hay bales placed along the edges helped to hold the side walls in place when the wind picked up. So for anyone with a little extra space, a caterpillar tunnel might be a nice, inexpensive option.

Another very simple season extension and pest suppression technique is to use large cans, like the ones in the food service industry for canned fruit and vegetables. Simply cut out both ends of the cylinder and place the large can over your early seedlings. This technique creates a mini greenhouse for the seedling and, surprisingly, protects the plants from pests. We use these cans for our kale every year, and the kale grows beautifully without impact from the infamous flea beetles.

So as you are perusing your seed catalogs and planning your garden, consider boosting your garden’s performance with the use of some season extensions. Below are some useful websites you might want to visit.