What Does it Mean to “Harden Off” Seedlings?

I often get this question this time of year. You can hardly wait to get your tomatoes in the ground! You’ve grown the plants out with great care. You’ve babied them.

You desperately want to plant them in the ground.  You take your hand or trowel and plant them in the cold ground. You water the seedlings and hope they will quickly grow. Uh oh, something is wrong! For some reason the plants don’t look so good after a couple of days in the soil. They look like they are burnt or dying. What did I do wrong?

Here are the steps you must take for  successful transplant.

  1. A seedling must be 45 – 60 days old prior to transplanting into your garden or container.
  2. Seven (7) to 10 days prior to transplant, start to wean the plants to use less water. Only water enough to prevent wilting.
  3. Treat your seedlings with seaweed emulsion, either by spraying or watering with a one (1) tablespoon per gallon of water solution.
  4. Take the seedlings outside for 2 hours the first day. Make sure you do this on a warm day with little wind. A cold wind could damage the seedlings. If you are using a cold frame*, completely opening the lid. Use the same guidelines as above.
  5. Each day increase the time outside by one (1) to two (2) hours.
  6. By the tenth day the seedlings will be tough enough to take the rigors of full sunlight and wind.
  7. Now you may safely plant your seedlings outside.

*Cold frame – a box with no bottom that has a hinged or removable clear or translucent top. The top may be opened or closed when the temperature outside is too cold or too warm. The box may be constructed out of  hay/straw bales, glass, poly carbonate, wood, etc.

cold-frame

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