FROG is a cordial group of veteran and novice Organic Gardeners who enjoy sharing their knowledge and enthusiasm.
Meetings are held  7pm on 3rd Thursday monthly
September through April at
Denver Presbytery Center
1710 S. Grant St., Denver  80210

(Location is 3 blocks east of Broadway, 4 blocks north of Evans.  Free parking in lot south of the building--enter from alley on east side of the building or driveway on the south side of building.)


“Hardening off” is the process of moving plants outdoors for a portion of the day to gradually introduce them to the direct sunlight, dry air, and cold nights. 

Good gardeners aren’t perfect. And the process of hardening off doesn’t have to be executed perfectly or uniformly to be highly successful. If you forget to take your plants out one morning before work, just start back up the next day. If the spot you chose for them becomes too sunny as the day went on, all is not lost. Plants are a forgiving lot and will hang in with you as long as you give them a little attention.

Below are step-by-step instructions given by Norma Rossel, Quality Assurance Manager for Johnny's Selected Seeds.

  • Harden off gradually, so that seedlings become accustomed to strong sunlight, cool nights and less-frequent watering over a 7-10 day period.
  • On a mild day, start with 2-3 hours of sun in a sheltered location.
  • Protect seedlings from strong sun, wind, hard rain and cool temperatures.
  • Increase exposure to sunlight a few additional hours at a time and gradually reduce frequency of watering, but do not allow seedlings to wilt.  Avoid fertilizing.
  • Keep an eye on the weather and listen to the low temperature prediction. If temperatures below the crop's minimum are forecast, bring the plants indoors or close the cold frame and cover it with a blanket or other insulation.
  • Know the relative hardiness of various crops. Onions and brassicas are hardy and can take temperatures in the 40's. After they are well hardened off, light frosts won't hurt them. Warm-season crops such as tomatoes, eggplants, melons and cucumbers prefer warm nights, at least 60° F. They can't stand below-freezing temperatures, even after hardening off.
  • Gradually increase exposure to cold.
  • After transplanting to the garden, use a weak fertilizer solution to get transplants growing again and to help avoid transplant shock.  Be sure to water plants after hardening them off.

The terms "hardy" and "tender" relate to whether a crop can withstand frost. Hardy plants can, tender crops can't and half-hardy ones may be able to take brief, light frosts.

Hardy plants, can be hardened off when the outside temperature is consistently above 40° F.  Half-Hardy plants may be hardened off at 45° F.

Recommended Minimum Temperatures 
  • Hardy 40° F. Broccoli, Brussels sprouts, kohlrabi, cabbage, onions, leeks, parsley
  • Half-Hardy 45° F. Celery, Chinese cabbage, lettuce, endive
  • Tender:
50° F. Squash, pumpkin, sweet corn
60° F. Cucumber, muskmelon
65° F. Basil, tomatoes, peppers

There is a bit of hassle involved in schlepping the plants outdoors and back in again each day over a week. But after gently caring for your plants for weeks, the added effort is good insurance that your plants will leave your nest safely and do well in your garden.

Don't forget that waterwalls will also help to stabilize temperatures.  Waterwalls are used a great deal in the Front Range.
An organic garden club since 1987 in mile-high Denver, Colorado.
Front Range Organic Gardeners, Inc.

Questions on meetings
or membership?

Call 303-744-7871