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Hardening Off Your Transplants

In New England, heat-loving plants such as tomatoes, peppers, and eggplants must be started indoors, ideally in a greenhouse, in order to mature during our growing season. Any plant started in a greenhouse, however, must be “hardened off” before it can be planted in the garden. Hardening off is the process of exposing a plant to outdoor conditions (like wind, sun and irregular watering) to help them transition to life in the garden.

Follow these steps to harden off transplants:

  1. Harden off transplants gradually. A 7-10 day period works well.
  2. Keep transplants in a sunny, protected place in your home.
  3. Expose transplants to 2-3 hours of sunlight in a protected space outside.
  4. Repeat this daily, increasing exposure to sunlight outdoors gradually (by an hour or two each day)
  5. Pay attention to weather forecasts and do not leave plants outdoors if temperatures are forecasted to be lower than what each plant can tolerate. Note: Hardy plants can tolerate temps in the 40s° F while tender crops require at least 60° F.
  6. Continue to water plants regularly; however, allow plants to dry out slightly by slowly reducing how often you water. Do not allow plants to wilt!

When planting your transplants, remember:

  1. Check the roots: if the roots are rootbound or have wrapped around and around the plant, loosen them up by gently tickling them apart
  2. Transplant on cloudy days or early in the morning
  3. Make sure plants are moist before planting
  4. Water immediately after planting and for the next several days
  5. Water the base of the plant not the leaves. 
  6. Tip:  Try filling a bucket with water and using a cup to pour water around plant's base so it will seep into the roots.

What to Plant - May

May 15 is the earliest date gardeners use as the frost-free date in the Boston area. This means that May is the month when we begin to plant heat-loving crops such as tomatoes and eggplants, and stop planting cold-loving pants such as peas. Here are some ideas of what to plant this month:

Before May 15

Except for peas, any of the vegetables mentioned in the April newsletter: spinach, radishes, turnips, beets, Swiss chard, lettuce, carrots, kale, collards, bok choi

After May 15

Note:  Since this is the earliest possible time for planting warm-weather crops, if you're a beginner gardener, we suggest waiting until May 22. If you want to plant early, be sure to check the 10-day weather forecast to make sure all frosts have passed. 

From seed: beans, cilantro

From transplant or seed: cucumbers, melons, summer squash / zucchini, basil (transplant preferred), dill

Transplant only: tomatoes, eggplant, peppers, parsley

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