Thursday, January 28, 2010;
Greenhouses are generally classified as cool greenhouses or warm greenhouses.
Cool greenhouses are kept at overnight winter temperatures in the 40s, allowing the safe storage of frost-sensitive plants in relative dormancy. Vegetables and annuals can be started from seed in February and March. Use an electric warming mat to provide bottom heat to speed germination.
Warm greenhouses are kept at a minimum of 55 degrees. Heating costs are higher, but a warm house promotes active growth and flowering of tender plants, including orchids.