A hotbed allows gardeners to get a head start on the gardening season or extend it. The heated bottom promotes faster seed germination, so gardeners can start seeds earlier in the season. Cuttings and divisions will also take root faster in a hotbed environment. Hotbeds extend the gardening season in fall by adding weeks to the normal growing season. Learning to use a hotbed can be beneficial to all gardeners.
What Is a Hotbed
A hotbed is cold frame about 3 feet wide and 6 feet long that is 18 inches high in the back sloping to 12 inches high in the front. The main difference between a hotbed and cold frame is that a hot bed has a heat source to warm the soil. The boxes are generally made with rot-resistant wood or concrete blocks. The top is made of a sheet of glass, fiberglass or clear plastic, and is easy to raise for ventilation and lower to conserve heat.
Extending the Growing Season
In fall, a hotbed keeps temperatures warm enough to grow some plants during cold weather. These beds are often used to grow cool-season vegetables from seed to maturity out of season, when normal outdoors temperatures would not permit it. Hotbeds, when used in spring or fall, keep soil at 75 degrees F, which is ideal for seed germination and support growth of most plants.
The Best Location for a Hotbed
Even though hotbeds are generally heated, the best place for the beds is a sunny location with well-draining soil where the bed is protected from the wind. The slant of the roof should face south to accumulate heat. The bed also needs to be in an area close to an electrical and water source.
Seedlings grown in a hotbed must be hardened off before planting in garden. Hardening off is the process of allowing the seedlings to slowly become acclimated to their new environment before planting them outdoors. To do so, gradually expose plants to the to open-air conditions during their last week in the hotbed. Gardeners also need to perform certain hotbed tasks each season.
In spring, after the danger of frost has passed, gardeners can trans plant seedlings from the hotbed into the garden after hardening off. Spring is also time to harvest cool-season crops grown in hotbeds.
In late winter, gardeners can sow annual flower and vegetable seeds in the hotbed so that seedlings are ready for the garden once the weather warms in spring. This is also the time to plant the seeds for cool-season vegetables that a gardener wishes to grow to maturity in the bed.
In fall, gardeners can sow seeds for lettuce, spinach of other cool-season vegetables they wish to grow to maturity and harvest in spring.
In winter, it may become necessary to use an insulating cover for the hotbed to conserve heat during extremely cold temperatures. Gardeners can use straw to cover the hotbed and prevent heat loss. Place straw on top and around the hotbed to avoid heat loss through the frame joints and prevent drafts.