By Eric Priebe ©2012
Penn State Master Gardener
As fall approaches, the days are becoming shorter and temperatures are cooling. Fall's first frost (typically late October here in Western Pennsylvania) will end the growing season for many garden vegetable crops.
But wait, that's just the end of the summer growing season. Now is the time to sow seeds for fall crops. The upcoming combination of warm days and cool nights are ideal for growing cool-season vegetables like lettuce, beets, carrots, broccoli, cabbage and chard. Autumn conditions add extra sweetness and crispness and reduce many common pest and disease problems. With some planning and preparation, you can extend the growing season a few weeks, a couple months or even all the way through winter to enjoy four seasons of gardening.
A full sun location maximizes the available solar energy. The shorter days of spring and fall provide less daylight for plants to photosynthesize. Add two weeks to seed packets' recommended days to maturity for the slower growth that occurs during shorter days.
One night of less than 32 degrees usually ends all but the hardiest garden crops. In an emergency, cover plants overnight with sheets, blankets or cardboard boxes.
Frost is unique on glass but deadly to tender plants
Locate your garden near a windbreak like a fence or hedge to reduce potentially damaging wind. Combined with cooler temperatures, wind accelerates drying and shortens the growing season.
Boost soil temperatures to improve seed germination and help crops grow longer into the fall. Use mulch to moderate soil temperature and to shield your plants from low temperatures. Black plastic or garden fabric can increase soil temperatures and retain heat.
Choose plant varieties that will match your early or late season production goals. For example, some varieties of broccoli thrive in cold spring soils but go to seed quickly once warm weather arrives. Other varieties tolerate mid-summer heat, and still others thrive in the low light conditions and cold temperatures of late fall.
Sow seeds every few weeks for a continuous harvest. You will enjoy more vegetables at the peak of their maturity as well as free up garden space as older crops decline.
Don't forget the bees! If you cover crops such as peas, strawberries, beans and squash that require pollination to produce a harvest, remove or temporarily lift fabric from the beds during the day to allow bees to do their work. Self-pollinating plants, such as tomatoes, can be left covered during cooler temperatures.
Consider how long you want to stretch the season and the amount of time and resources you are willing to invest. If you want to extend your harvest season year-round, you will likely need a greenhouse and should be ready to provide daily attention. On the other hand, if you just want a few extra weeks of ripe tomatoes in the fall and more salad greens in the spring and fall, using garden fabric is easy and inexpensive.
An inexpensive and easy first step in season extending, garden fabric provides an excellent protection from cooler temperatures, frost, wind and insects. Made of spun polyester or polypropylene, garden fabric is sun-, air- and water-permeable. It is available in a variety of thicknesses capable of protecting plants down to 25 degrees. Drape the fabric right over garden plants or use wire hoops to support it. Secure the edges of the fabric with garden stakes or soil. Don't forget to check the plants under the fabric at least weekly for water and weed control. Garden fabric should last for many years. When not in use, fold and store away from light and moisture.
Enclosures with a clear top, cold frames capture sunlight to create a warm microclimate to allow plants to be started earlier in the spring and survive longer into the fall and winter. Cold frame kits are readily available and can be assembled quickly with basic tools. Handy gardeners can design and build their own cold frame, often from used materials. A cold frame starts with an enclosure large enough for your mature plants topped with a clear sash made from an old window, plastic or fiberglass. The sash must open for ventilation and close tightly to retain heat. Daily monitoring or automatic control is required to adjust ventilation. Plants can be quickly damaged from too much heat on sunny days.
Frost on tender Beech leaves in late-Spring
Both hobbyists and farmers are increasingly using solar tunnels as affordable and highly effective structures to extend the gardening season. A tunnel is constructed of a frame (typically metal pipes bent into arced hoops) covered with clear plastic sheeting specifically designed for gardening. During the day, solar energy is collected through the clear covering and retained within the structure throughout the night. Daily monitoring is required. Ventilation is critical as too much heat can be generated on sunny days, damaging cool-season plants.
Achieving four-season gardening will likely require a greenhouse that can provide extra insulation against very cold temperatures and stand up to heavy snow loads common here. When choosing a greenhouse, try to visit as many as possible in order to clarify your own greenhouse vision. Considering the options and making your plans is an exciting process.