How to Harden Off Broccoli

While broccoli is a hardy plant variety, you can't simply take broccoli seedlings you started indoors or purchased and plant them directly into your garden. The seedlings have to go through a process called "hardening off," which allows them to gradually become accustomed to more intense sunlight, winds, cool nights, temperature variations and less frequent watering. It can get a little tiresome dragging the plants in and out, so one option is to use a cold frame in the hardening off process.

Cold frame (optional)

Instructions

- 1
  Monitor your local weather conditions for a prediction of a stretch of days where the lows won’t fall below 35 F. Usually this will be a few weeks before you plan to plant the seedlings in the garden. Plan to start hardening off on the first milder day.
- 2
  Bring your seedlings outside to a sheltered area where there is some protection from the sun and wind. Leave the plants outside for two to three hours either in the early morning or the early evening when the sun is not as strong. Repeat this process for a few days.
- 3
  Increase the amount of exposure to weather conditions by gradually increasing the amount of time the seedlings are outside and by moving them out into the open. Do this over a one- to two-week period. To shorten this period, put the seedlings in a cold frame and open and close it over a five- to seven-day period.
- 4
  Monitor the seedlings for any sign of wilting or flopping over. If you see these signs, bring them inside.

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Vegetable Garden