How to Extend the Growing Season in a Greenhouse


A small hobby greenhouse can help you extend the summer growing season for plants that might get damaged by fall and winter frosts. A small greenhouse can extend the lives of potted plants such as sweet basil, potted peppers and ornamentals. Construct a simple greenhouse with a 2-by-4-foot frame covered by corrugated clear fiberglass panels. Adding shelves provides space to keep potted plants throughout the winter.

Step 1

Design your greenhouse to allow plenty of space for your potted plants. Bring them in shortly before the first fall frost. Hang the plants, place them on shelves, set them on the ground or grow them in a planter box.

Step 2

Hang shop lights or special grow lights to provide necessary light. Incandescent lights will generate a certain amount of heat, especially if high wattage (300 watts is recommended).

Step 3

Supply a heat source, especially if your winter temperatures frequently dip below 32 degrees Fahrenheit. Although your greenhouse will protect plants from direct frost, the temperature can drop too low for many plants to survive. You can supply heat with a space heater (expensive) or by creating a heat sink by filling gallon plastic jugs with water, which heat up during the day and retain warmth at night. Incandescent lights can also help.

Step 4

Set up one or more fans to keep the air circulating. Moving air will help prevent some fungal diseases that can run rampant in warm, still environments.

Step 5

Move tender plants such as potted citrus trees, orchids and certain palms into your greenhouse before the first fall frost arrives.

Tips and Warnings

  • Insects, snails and slugs can also thrive in your warm, snug greenhouse. If problems arise because of these creatures, spray them with insecticidal soap. Scatter diatomaceous earth or iron phosphate granules ("Sluggo") to deter snails and slugs.

Things You'll Need

  • Grow lights or fluorescent shop lights
  • Fans
  • Heater or heat sink (optional)
  • Insecticidal soap (optional)


  • Hobby Greenhouse Association
  • Hobby greenhouse

Who Can Help

  • Gardener's Supply
Keywords: greenhouse gardening, protecting plants, extending season

About this Author

Barbara Fahs lives on Hawaii island, where she has created Hiā€˜iaka's Healing Herb Garden. Barbara wrote "Super Simple Guide to Creating Hawaiian Gardens," and has been a professional writer since 1984. She contributes to Big Island Weekly, Ke Ola magazine, and She earned her B.A. at UCSB and her M.A. from San Jose State University.