Expert Advice for Greenhouse Growing

Enlarge Image Image Gallery A greenhouse can be small enough to fit in a corner of your garden, or large enough for a market gardener, as shown here. JASON HOUSTON

A greenhouse is one of the most valuable additions you can make to your property. If you want to be more self-reliant by raising more of your own food, a greenhouse — large or small — can help you meet many of your needs and goals. With a greenhouse, you can plant fall and winter crops to extend the growing season and enjoy fresh food year-round. It also can provide food and shelter for poultry and livestock, and it’s a great place to put worm bins. Here’s a little about my greenhouse, and the many ways I use it.

The Greenhouse Structure

Start with simple components. Most greenhouses are made from sheets of plastic stretched over a metal frame. You can buy a kit with all the essential components. Mine is a Paul Boers “gothic” style kit (the arches come to a peak at the top, which is better for shedding snow). I paid more up front to get 1½-inch galvanized steel pipe, rather than 1-inch, for added strength. If your area gets any snow or heavy wind, this heavier pipe is a good investment.

I also recommend using 6-mil plastic that has been treated to resist ultraviolet breakdown. It’s readily available from any greenhouse supply, and the version I use is guaranteed for four years. I use two layers of plastic with a small, energy-efficient blower to inflate the space in-between. The inflated “bubble” increases the insulating value of the cover, sheds snow more readily, and resists “chatter” in the wind, resulting in better wear.

Protect your foundation. When I first put up my greenhouse, I installed a wooden foundation to attach the “channel lock” into which the plastic cover is secured. Because I avoid using chemically treated wood, I used 2-by-8 pine boards with several coats of linseed oil. That was a bad idea — the boards rotted out after five years. My solution was to install a single course of 4-inch hollow concrete block on a small poured footer, then lock a better grade 2-by-4 (sealed against moisture) onto the top of the block foundation using J-bolts pushed into wet concrete in the holes of the blocks. The channel lock is still screwed into wood, but the wood is never in contact with earth or rain. With applications of sealant as needed, it should last as long as I do.

Choose the right size. The larger the greenhouse, the better its ability to buffer temperature extremes. That’s because a larger greenhouse will have a larger amount of thermal mass — in the form of soil — that is warmed by the sun during the day, resulting in warmer nighttime temperatures. Another reason to choose a larger greenhouse is that you’ll find more and more things you want to do with it.