Seed responses to light can control the timing of germination in the field, impacting seedling survival, as well as growth and fitness in subsequent life stages. Seeds that require light for germination are usually small.

Should I put my seeds in the sun?

Most seeds will not germinate without sunlight and will perform best with 12 to 16 hours each day. Indoors, place seed containers in a sunny, south-facing window and give the container a quarter turn each day to prevent the seedlings from overreaching toward the light and developing weak, elongated stems.

Do seeds need sun or heat?

Most seeds don’t need light to set off germination—though the seedling will need it later on to carry out photosynthesis for energy, when the seed’s food stores have been used up. Some seeds, however, need certain kinds or amounts of light to break dormancy—a kind of seed sleep, which we’ll look at a bit more later.