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Starting Seeds Indoors

Starting seeds indoors gives a head start on the gardening season and opens the door to growing endless varieties. And, it is a fun way to kick off the gardening season.

What You Will Need

  • Seeds of your favorite vegetables or flowers
  • Containers
  • Potting mix or peat pellets
  • Squirt bottle of Water
  • Sunny window or Fluorescent lights

When do I start seeds indoors?

It varies according to the plant and the date of the last frost in your area. In many areas of Massachusetts, the last frost date is usually around May 15th. Count back the number of weeks from when each vegetable is to be transplanted into the garden. That will tell you when to start your seeds indoors. Seeds of root crops should be sown directly into the garden.

As a guide, count back number of weeks from outdoor planting date for when to sow seeds indoors.

4-7 weeks Broccoli, brussel sprouts, cabbage and cauliflower
2-3 weeks Cucumbers, summer squash and melons
3-5 weeks Lettuce
7-9 weeks Eggplant,
6-8 weeks Onions, tomatoes and peppers


Seeds can be started in just about any kind of container such as trays, flats, pots, peat pots, compressed peat pellets or cut-off milk cartons. If the trays or pots have been used, it is a good idea to clean and sanitize them in a 10% bleach solution before use (1 part bleach to 9 parts water) and rinse.

Growing Mix

Use soilless potting mix for seeding such as an all-purpose houseplant type potting mix. Soilless mixes contain peat moss, vermiculite, perlite (or similar ingredients) and wetting agent (helps the mix hold water). Avoid using garden soil to prevent waterlogged soil, weeds, insects, and diseases.

Five Steps to Planting Seeds

  1. Slightly moisten potting soil before planting. Put potting mix in a bucket and add water to moisten. Time to get your hands dirty - mix it up.
  2. Loosely fill the containers to level with soil. Do not pack it down.
  3. Plant large seeds such as cucumber or muskmelon into the container they will be grown in. Press 2 or 3 seeds ¼ inch deep in the potting mix and cover gently with the same potting mix.
  4. Small seeds such as lettuce and peppers can either be seeded in rows and later transplanted or directly seeded and thinned. Small seeds will require less cover and some seeds will require no cover at all. The sowing instructions on the back of the seed packet will provide specific needs for the seed.
  5. Water lightly with warm water. A squirt bottle can be used to moisten newly planted seeds without disturbing them.


Funding from the Massachusetts Department of Agriculture