How old your seeds are should be considered—they lose their fertility after a period of time. A seed that doesn’t germinate may be due to several factors or a combination of overwatering, inconsistent temperatures (temperatures should ideally be above 70 F) or not enough dampness. Usually, an initial thorough soaking of the soil medium should be sufficient to bring the plant to the germination stage. Covering the planting box with plastic or a plastic cover, such as those found in most nurseries, will help maintain moisture. Germination is best in a dark room and warm area.
Generally, you can expect seedlings to emerge five to 10 days after they are sown. Higher temperatures will result in quicker germination, while lower temperatures will result in delayed germination. Be sure to maintain your seeds in the optimal temperature zone for the best results.