Fall celebrates the end of Colorado’s normal growing season with spectacular harvests. What can gardeners to do extend the harvest?

Question: How long is our growing season?

Answer: It depends. For Front Range elevations (4,300 feet to 7,500 feet), the average growing days is 50 to 150 days. Remember Labor Day week, where it was warm followed by three nights of below-freezing weather?

Q: How can one extend the growing season?

A: Key thing: frost protection! Recently, neighborhoods had sheets over gardens. We experienced “radiation” frost — light frost on a clear night without cloud cover. For “advective” frosts, when a cold front moves in and temperatures drop more than 6 to 10 degrees, more substantial systems are required. Soil heats up with sunshine and gives off heat at night. The key is to capture daytime heat with frost protection systems.

Q: What are frost protection systems?

A: Here’s a sampling of options, depending on how cold it gets:

• 2- to 3-degrees protection: sheets or blankets (but materials must stay dry.) To protect root crops (onions, beets, carrots, etc.), add 2 to 4 inches of extra leaves, straw or soil. Before the ground freezes, place straw bales over the row and dig when needed

Floating row covers: Transparent, light-weight cloth, available at garden centers, pre-packaged or open stock (widths of 12 feet by any length). Drape over the plants directly, tuck edges into soil, leave on to protect against frost, wind and some insect damage. Or drape row covers over a raised bed outfitted with wire or PVC hoops. I used this system to protect seedlings this spring and again this fall.

4 mil clear plastic sheeting over wire hoops: Sold in 10-by-25-foot rolls (as well as other sizes) at garden centers or hardware stores. It’s important that the plastic does not touch plant material. Make a “tunnel” on the ground or over the raised bed. Tuck sides and ends of plastic into soil. If left on during the day, the inside may heat up too much, causing plant injury. Consider cutting 2-inch air vents into the sides of plastic.

4 mil plastic sheeting over concrete reinforced mesh: Available at hardware and lumber suppliers in 5-by-50-foot to 5-by-100-foot rolls. Form stiff mesh into an arch (think Quonset hut). Attach 4-inch-wide raised bed with wood frame. Drape two pieces of plastic, one from each side, overlapping at the top. Anchor plastic sheets with cross-wise plastic strips (like belts) at 2- to 3-inch intervals. Pull plastic apart for ventilation, sliding the plastic down between “belts” and the mesh. Use big metal clips to secure the plastic. Cost is higher than the “tunnels” or floating row cover systems, but allows for greater extension in spring and fall.

Add Christmas tree lights inside for 6- to 18-degrees protection: Hang incandescent lights (not minis or LEDs) under plastic with one 25-bulb string per 4-by-5-foot frame.

Add a space blanket: Drape an aluminum space blanket over the wire frame (foil side down); remove during the day.

If you’re hooked on extending, consider a hobby greenhouse. You can overwinter many plants, extend the growing season and be more energy efficient. Follow optimal energy specifications for traditional, passive or active solar systems. The key to success is the orientation of structure, reducing heat loss, selecting the appropriate materials and greenhouse management.

For more details, see CSU fact sheets 7.220, “Colorado Gardening: Challenge to Newcomers”; 7.22, “Frost Protection & Extending the Growing Season”; 7.23, “Growing Vegetables in a Hobby Greenhouse”; 7.601, “Storage of Homegrown Vegetables”; 746, “Climate Summary: Fort Collins, Greeley and Estes Park.” All are available at www.ext.colostate.edu.

The author has received training through Colorado State University Extension's Master Gardener program and is a Master Gardener volunteer for Larimer County.