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Starting Seeds Indoors: Caring for Your Seedlings

How to Grow Healthy Seedlings

Once seeds have sprouted, remove the plastic cover!


Place the containers in a bright sunny window (the sooner the better) and turn slightly each day. Or, grow them under fluorescent lights for 12‐16 hours per day. Space the lights as close as possible (about 5”) above the seedlings; lift the lights as plants grow.

Plants will stretch to become “leggy” and weak without enough light, or if the temperature is too warm.


Tomato, pepper, eggplant, cucumber, melon and squash seedlings grow best at 60°F at night and 70°‐75°F during the day.


Water seedlings with room temperature water. Water sparingly until seedlings have become sturdy. Overwatering small seedlings can cause stems and roots to rot!

Transplant or Thin

After large seeded seedlings have emerged, thin to 1 or 2 per pot by pinching off or carefully pulling out extra plants. After the new seedlings from small seeded crops have formed a couple of sets of leaves, do one of the following: (1.) transplant to individual pots or (2.) thin to make room for each seedling to have its own space, not touching its neighbor.

Hardening Off

About one week prior to planting in the garden, gradually expose seedlings to longer periods of time outdoors. At the same time, reduce watering to a minimum, but don’t let the plants wilt. This process will help the plants adjust to outdoor conditions and is called “hardening off”.

When to Plant Seedlings in the Garden

In many areas of Massachusetts, the last frost date is usually around May 15th. Cool weather crops, such as broccoli, cabbage, lettuce and Brussels sprouts, can tolerate a little frost. Transplant them two weeks or so prior to the last expected frost date.

Wait to plant warm season crops, such as tomato, pepper, eggplant and cucumber, melon and squash until all danger of frost is past, when air temperatures and the soil temperature warm to 60° ‐ 65°F.