Starting Seeds Indoors

Starting seeds indoors allows plants to get a head start before they can be planted outdoors. With just some planning, a little extra care, and lighting, many plants are easily propagated this way. Refer to the seed packet for requirements and germination time specific to each plant. Below is a general guideline for when to sow some common plants and some guidelines for starting seeds indoors.

CropsWeeks from Sowing to Transplanting
Basil4-6
Broccoli6-8
Cabbage6-8
Cauliflower6-8
Collards6-8
Cucumber4
Eggplant8-10
Kale6-8
Lettuce4-5
Melons4
Onions8-12
Parsley9-10
Peppers8-10
Pumpkins4
Spinach4-6
Squash4
Swiss Chard4-6
Tomatoes6-8

Container

Use seed trays, peat pots, Jiffy 7 peat pellets, or other shallow container with good drainage. Sanitize any used containers with a solution of 1 part bleach and 10 parts water.

Soil

Use a sterile seed starting soil medium such as vermiculite or Espoma Organic Seed Starter Mix. Water soil medium and allow it to drain before seeding.

Seeding

Sow more seeds than the number of plants you actually need. Once seeds germinate and develop into seedlings, thin them out by pinching the smallest seedlings to leave the strongest seedlings to develop.

Covering containers with plastic will help hold in moisture during germination. Be careful not to let them get too hot and remove plastic once the seeds germinate.

Light

Keep in bright light once seeds germinate (when the seed opens and plant parts begin to form), and rotate often for straight growth. Some seedlings will grow well in a sunny, southern-facing window, but may become spindly if they aren’t getting enough light. Supplemental lighting is optimal and sometimes necessary for certain plants. Check seed packets for lighting needs.

When using supplemental lighting, place seeded containers under full spectrum fluorescent lights that are set about 5 inches above the tallest part of the plants. Keep the lights on 16 hours a day and then gradually decrease time to 12 hours a day, as they mature. As the seedlings grow, adjust the light height to remain 5 inches above. One neat way to do this is by placing seedlings on stacked shoe boxes. As the seedlings grow, remove a shoe box below to adjust the distance from the light for each individual tray.

Temperature

Containers should be kept gently warm while germinating with a heating mat. Once germinated, seedlings should be kept at 65-75 degrees F.

Seedling Tips

  • – Make sure there is good air circulation to prevent damping off. A small fan works well and will help strengthen stems.
  • – Gently brush hand across several times per day to strengthen stems & keep stocky.

Water

Keep soil moderately moist, but not wet. To avoid disturbing or damaging the seedlings, water gently from above or water from below by placing tray in a container and watering in the container. Always water early in the day to prevent disease, rather than late in the day or after dark. Cookie sheets are useful for placing under trays to catch excess water.

Fertilizer

Once the seedlings start to form their second set of leaves, apply a water-soluble fertilizer weekly at half the recommended rate.

Transplanting

Before transplanting, acclimate the plants to their new environment with a slow introduction as described in Hardening Off Greenhouse-Grown Plants.