Why Don't Seeds Need Sunlight to Germinate?

Seeds typically do not require sunlight for germination because most of their nutritional needs for the germination phase of a plant's life are contained within the seed itself. Conversely, some seeds do require light to germinate. Although this is atypical, such seeds mustn't be buried in soil.

During the germination phase, most plants require three basic factors in order to get started: proper soil pH, moisture and a temperature that's appropriate to the specific plant's requirements. The correct temperature for most plants falls somewhere between 40 and 104 degrees Fahrenheit.

When seeds that require darkness for germination have issues sprouting, small, occasional exposure to white light can stimulate the seed to the point of germination, although this does not work in all instances.

The typical rule of thumb in regard to a plant requiring sunlight to germinate is the smaller the seed, the more likely it is to need light. Such seeds should be placed on top of the soil in order to collect sunlight to stimulate germination.

Some plants have even more specific light requirements during germination. The Grand Rapids variety of lettuce, for example, is only stimulated to germination by red light at a wavelength of about 660 nanometres.