After starting seeds indoors, follow these tips and guidelines for good care of your young plants.
After germination, seedlings require strong light from grow lights. Natural light from a window is seldom enough for good, strong seedling growth. Plant stems usually stretch and lean towards the light and will not produce sturdy plants. Acceptable plant growth usually only occurs in south-facing bay windows or solariums.
Fluorescent light fixtures and tubes are the best choices for growing seedlings indoors. (See details on our grow lights page.) Place your plants 1-2” beneath a fluorescent fixture for 14 to 16 hours a day. This will increase light intensity and keep plants stocky and strong. Attaching thin chain or wire to either end of your light fixture will allow you to raise and lower the tubes.
Tomato and cabbage family plants are prone to stretch toward the light. Pepper, eggplant, and lettuce will stay compact.
Tomato seedlings stretched from lack of light
Lack of uniform watering, overwatering, and drying out are problems associated with seeding care. Wait until the top of your growing medium is nearly dry before watering. You can either apply water to the surface or allow your growing medium to wick up water by setting your containers on a shallow pan. Water to keep the growing media moist, but not wet.
The goal is to keep the root systems supplied with water and oxygen. If your containers are saturated with water, the roots will stop growing and pathogenic fungi that like wet soil can infect your plants. The “damping-off” fungi, Pythium, Phytophthora, and Rhizoctonia, can quickly kill a container of seedlings if the growing media is kept too wet. If an infection occurs, dispose of the plants and growing medium, wash containers and tools to remove any debris, and soak them for 1-2 minutes in a solution of 1 part chlorine bleach to 10 parts water. Then rinse with clean water.
Hold back on fertilizing your seedlings. Most potting mixes contain enough fertilizer to grow a seedling for 5-6 weeks.
After germination, seedlings can be given somewhat cooler conditions, with a 55-60°F night temperature and a 65-70°F day reading.
If plants have not been seeded in individual containers, they must be potted up (a.k.a. “pricking out” or “transplanting up”) into a larger individual container to give them proper growing space. One of the most common mistakes gardeners make is leaving seedlings in the seed flat too long. The ideal time to transplant young seedlings is when they are small and there is little danger of setback from root shock. This is usually about the time the first “true leaves” appear above or between the cotyledon leaves (the cotyledons or “seed leaves” are the first leaves to appear).
The 2 lower leaves are cotyledons. The 2 leaves in
the center are true leaves.
Broccoli raab seedling ready for transplant
Broccoli raab seedling after transplant
These tomato seedlings have outgrown the
containers and must be transplanted into larger
containers until it is time to plant them outside
Next, learn about hardening off vegetable seedlings.