Winter Greenhouse Activities

Temperature and Ventilation

• Temperature and ventilation requirements in the winter greenhouse are different from those of other seasons. Automatic ventilators should be switched to manual or put on a solar controller so they only open on sunny days and close tightly at night. Maintain the winter greenhouse temperature at a minimum of 45 degrees Fahrenheit at night and 55 degrees during the day. Temperature and ventilation are key to growing during the winter months and are important enough that you should invest in automatic systems and backup power, if possible. Cold houses, or hoop houses without winter heat and light, require attention to temperature and ventilation as well, since you will need to cover ground crops and monitor temperatures.

Sanitation and Insulation

• Winter is the perfect time to attend to sanitation and insulation needs in the greenhouse. In the early winter, before freezing temperatures begin, wash down all areas of the greenhouse that allow light to enter. Wash all shelves, benches and storage areas. Check for wet areas that may promote mold and fungus, and look for any insect evidence or activity. Wash and sterilize all tools and potting items that will be reused. Restock soil, seed and plant food supplies, and remove all debris. Check all seams, cracks, walls and doors for spaces and air drafts, and seal them with foam insulation, caulk and weatherproofing materials as necessary. Add insulation where needed, using bubble insulation or winter panels. Unheated greenhouses benefit from attention to sanitation and insulation as well. Add an insulating layer over the top or run fans only on sunny days. Inspect the greenhouse for signs of digging and burrowing animals.

Monitor Light Levels

• Winter's lower sunlight requires attention to light levels for greenhouse plants. Most plants need 12 to 16 hours of light daily for healthy growth. Watch light availability, and supplement it with artificial light when necessary. Consider automatic lighting from January through March. Hoop houses without heat won't have as much need for attention to light, but it's still valuable to note the amount of light available daily, weekly and monthly throughout the winter.

Sow Flowers and Vegetables

• After greenhouse flower, herb and vegetable crops are harvested in the late fall, prepare winter crops for cultivation. Sow flower and vegetable seeds such as salvia, hollyhocks, snapdragons, tomatoes, beans, onions and seed potatoes. Plant any cuttings that are ready, and tend all permanent greenhouse plants such as grapes, perennial flowers such as geraniums and fruit trees.