By using season extending techniques, you can harvest vegetables earlier and later in the season than would normally be possible. The three main goals of any season extending strategies should be;
1) protecting plants from cold temperatures and freezes, 2) protecting plants from drying winds, and 3) creating favorable temperature conditions around the plant for growth.
In addition, attention should be paid in selecting varieties that are the most cold tolerant for early and late crops.
To protect plants and increase temperatures around the plant, heat trapping materials and devices are used. Water is the most useful tool for absorbing heat and releasing it later - moist soils and water filled containers are potential heat sinks. Using clear or green plastic mulch on the soil will raise soil temperatures considerably during the day when the sun is shining. At night that heat is radiated back around the plants. When combined with an insulating cover of spun or foam type material (usually plastic) placed over the plants at night, temperatures will remain 10-20 degrees higher than the surrounding air. Straw and other natural mulch material can also be used as night insulation but is more difficult to apply and remove. Clear row covers also help to increase temperatures but have little or no insulating effect. Tubes, bottles, pipes, barrels, and walls of water are all examples of the use of water as a sink to trap and the release heat. When used in combination with insulating covers or heat trapping plastic mulches, these additional heat sinks offer greater cold protection and raised temperatures for enhanced plant growth.
Another interesting old fashioned season extending method is to make use of the heat that is given off by microorganisms when organic matter is being decomposed (like the center of your compost pile). In this system, beds are constructed and filled with a straw and manure (horse or cattle) mixture. Soil is placed on top and plants are gown over the manure. To keep this system going, aeration holes are needed (so it does not go anaerobic) and the manure-straw mix must be sufficiently deep to last for the desired period.
Wind protection is also key in extending the season. In early spring and late fall, cool, drying winds can cause plant desiccation and direct injury (by whipping the plants around). Wind breaks are essential to prevent this injury. If your garden is exposed, plant wind breaks on the side or end where the prevailing winds come from. If you cannot plant permanent wind breaks, use tall growing covers such as rye (to protect spring planted crops) or millets (to protect late planted crops ) planted around your garden. Another option is to make use of clear plastic slit row covers or light weight spun plastic row covers (that allow sufficient light in) for wind protection.
KP, WA, entered 1999-12-17