Seedlings need a lot of light to grow into sturdy, healthy plants. Chances are that you do not have enough natural light in your home to grow robust seedlings. Even a south-facing window usually will not do the job. You can, however, use artificial light (i.e., grow lights) to achieve the right amount of light required by seedlings.

Keep the lights as close to the seedlings as possible without touching them (2 to 3 inches). When seedlings first appear, keep the lights turned on for 12 to 16 hours per day. To reduce your hands-on time, use a timer to turn the lights on and off automatically.

Seeds require a certain temperature in order to germinate. Each plant has a specific optimum and a range within which germination will occur. The closer the temperature is to optimum, the quicker germination will occur. Most seeds germinate when the soil temperature is between 20° and 30°C/68° and 86°F. Once germination occurs, the optimum growing temperature for the seedling is about 10°C/50°F cooler than the optimum germination temperature.

Moisture is critical for germinating seeds. They like a moist but not soggy environment. Seeds require oxygen and if kept in a waterlogged state may rot. On the other hand, if the soil dries out, the seed will lose whatever water it has absorbed and will die. Finding the middle ground can be difficult and comes easier with practice. After sowing the seeds, mist the tray with water and cover it with plastic wrap, a plastic bag, glass, or plexiglass to seal in moisture.

As soon as the seed germinates remove the covering. Ventilation and air circulation are also important to discourage damping off diseases. Check the seedlings frequently (as much as daily) for moisture. Thoroughly water the seedlings when the soil surface becomes dry to the touch.