Norman A. Plate
Give them warmth and light
Seedlings of edible crops need bright light to develop properly; when grown in conditions that are too dark, the seedlings are spindly and weak. If you don’t have a suitable place for your seedlings, try growing them under fluorescent lights. As soon as the seeds sprout, give them 12 to 14 hours of light each day, setting the light fixture 6 to 8 inches above the tops of the plants.
Seeds of heat-loving summer crops need warm soil to germinate quickly and strongly. Thin waterproof heating mats placed under the containers keep the soil 15 to 20°F/8 to 11°C above room temperature.
Nurseries and mail-order catalogs offer both fluorescent light kits and heating mats.
Avoid "damping off" trouble
If your seedlings suddenly collapse and die, one of the fungal diseases called "damping off" or "seed and seedling rot" may be to blame. In one type of damping off, the seedling's stem collapses at or near the soil surface; in another type, the seedling rots before it emerges from the soil, or the seed decays before it even sprouts.
To prevent these problems, use pasteurized potting mix and new or thoroughly washed and disinfected containers.
Take care not to overwater seedlings; be sure to provide good air circulation and ventilation, so tops of seedlings stay dry and standing moisture is kept to a minimum. Thinning seedlings to eliminate crowding is also helpful.