Painting shelves and reflectors with a flat white paint will increase the amount of light reaching the plants. Lights are easily attached from the ceiling or a stand using furnace chain and S-hooks. The S-hooks allow you to adjust the height of the fixtures upwards as the plants grow. Seedlings require more intense light than more mature plants. Insufficient light results in legginess, excessively large gaps between leaves, and pale stems and leaves.
Plants usually require a certain 'photo-period' or time during which they have light.
Any longer than this can be harmful. An automatic timer is a very worthwhile investment. Temperature Requirements Remember, most seeds require a fairly warm soil temperature in order to germinate. Check the optimum soil temperatures for the germination of a particular species. Once germination has occurred, the seedlings will grow better at a lower temperature, usually about 10 degrees lower than their germination requirements.