In part one of this two part series, we discussed Agribon™, a row cover that shields plants from frost, wind, and insects. In part two we will discuss greenhouses and high tunnels, economical structures that can add to the bottom line (or feed a gardener's addiction) by allowing four season crop production in most climates.
Growers can control the temperature, light, and even humidity inside a relatively inexpensive high tunnel. The framing of a high tunnel is permanent and quite strong. They can fit in a backyard or a farm field, with sizes varying from 14' x 24' to 30' x 96'. In areas where the weather begins to cool by September, these larger structures give the gardener the flexibility to extend the growing season into late October or mid-November. They can also help you to get a jump on your spring planting by allowing you to get into the ground as early as February or March.
One way to increase the efficiency of any greenhouse structure is through the use of a "heat sink". By installing 5 gallon buckets or 55 gallon drums full of water within the structure, passive heat will be captured during the day and given off at night to keep the temperature within the environs from fluctuating to extremes. In northern climes, an electric or gas heater may be necessary to maintain a sufficient night time temperature through the coldest part of the winter. During the hot summer days the walls of the high tunnel can be rolled up and the automatic roof vents opened by temperature activated gas filled piston hinges to cool off the tunnel.
While the siting and structure of a high tunnel is permanent, the crops can be rotated, row crops being the most space efficient way to grow. Any equipment (tillers and small tractors) necessary to work the soil will easily fit inside. Drip tape, a main line with emitters punched in, or overhead spray down the middle are all ways to provide a closed and efficient irrigation system.
If you are growing for market, a high tunnel may be a viable way to get your crops to market a month or two sooner than the competition and extend your season too. If you're a backyard grower the smaller high tunnels, the Solexx greenhouse, or even Agribon™ row cover may make sense and will protect your late harvested or early planted crops.