Start vegetable seeds indoors for garden planting in spring

Although the seeds of vegetables such as root crops, beans, peas, and corn should be sown directly in the garden, some vegetable seeds – such as broccoli, brussels sprouts, eggplant, celery, tomatoes, peppers, and head lettuce – grow more successfully when started indoors.

There are several good reasons for starting some seeds indoors:

  • Because of the length of the growing season, some plants won’t produce unless given a head start.
  • Plants will be more productive if the growing season is lengthened.
  • Some seeds are small and might wash away if sown outdoors.
  • When a plant arrives in the garden with some growth behind it, it has the vigor to withstand some of the common outdoor hazards such as birds, insects, and weeds.

Containers

Anything that is the right size, can hold growing medium, and has proper drainage can be used to hold germinating seeds. The traditional method of starting seeds is to start them in a flat, then transplant the seedlings, when they have grown enough, into individual pots. Seed flats can be purchased or homemade, any length and width, as long as they are 3 to 3½ inches deep to accommodate root development.

Clay or plastic pots can be used for germination – as can margarine or cottage cheese tubs, cut-off milk cartons, and similar recycled containers – but individual plantable pots have one distinct advantage: You can plant the pot you sow the seed in, without disturbing the plant’s roots by transplanting. Plantable pots are made of peat or other fibrous material that will decompose once placed in the ground, and they can be purchased at most garden centers.

Germinating medium

The best medium for germinating seeds is a sterile, soilless mix of sphagnum peat moss with perlite. This is a lightweight mix blended especially for seed starting, and it is enriched with plant food to help build strong roots quickly. Starting seeds in garden soil is not recommended, since garden soil usually does not have the proper drainage and aeration for container use. Garden soil also may carry disease, insects, and weed seeds.

Sowing seeds

Before you start, refer to the chart below, which shows the number of weeks common vegetables need to grow from seed to transplant size. Count backward from your projected outdoor planting date to find the right time to start seeds indoors.

Sow one or two large seeds into individual pots; sow small seeds in rows in flats. Large seeds can be placed by hand; small ones, by tapping the seed packet. Don’t sow seeds too close together, since seedlings will need room for root growth, light, and air. Between seeds, leave a space at least as large as the diameter of the seed. Small seeds should not be covered; just press them into the surface of the growing medium. Cover other seeds with potting mix to a thickness of one to two times their diameter. Seal the pots or flats in a plastic bag and set them where the temperature is right for germination.

Seedling care

Once seedlings have germinated, remove the bag and place the container in full sunlight for 12 hours a day, if possible. If they can’t get that much sun, grow the seedlings under fluoresscent lights when the plants are 3 to 6 inches tall. Keep the growing medium evenly moist, but not wet, and the temperature 70-75°F during the day and 60-65°F at night.

When the first true leaves appear, start feeding the seedlings once a week with all-purpose plant food mixed with water per label directions.

Time Needed To Grow To Transplant Size

Vegetable Weeks
Artichoke 4-6
Asparagus 12-14
Broccoli 5-7
Brussels sprouts 4-6
Cabbage 5-7
Cauliflower 5-7
Celery 10-12
Chives 6-8
Collards 4-6
Cucumber 4
Eggplant 6-9
Endive 4-6
Kale 4-6
Kohlrabi 4-6
Lettuce 3-5
Okra 4-6
Onion 8
Pepper 6-8
Spinach 6-8
Squash 3-4