Vigorous plants such as tomatoes and herbs can be started indoors early from seed to provide an early harvest once they are transplanted in the ground. It is also a good way for green-thumb gardeners to get a jump on the growing season and relieve the winter blues before the time for outdoor gardening begins.
When to Start Seed
The optimal time to start seeds indoors will depend on when you can move them outdoors. To determine this, you will need to know the last average frost date for your area. This is a factor determined by averaging the last frost date for prior years. You can find out the last average frost date for your area by checking the Farmer's Almanac or your county extension service.
When you purchase seeds, the packages will have instructions printed on them as to how far in advance the seeds should be planted indoors. Plants such as onions should be grown up to 10 weeks before being moved outdoors, while cucumber plants may take as little as 3 weeks to grow indoors.
The best containers for starting seeds are seed trays with individual cells for seeds, says University of Minnesota Extension. You can start an individual seed in each cell container. This will keep the seedling roots from growing into each other and becoming damaged as you have to separate the container. These types of containers are frequently sold in garden centers with clear plastic domes over them that help hold in heat and moisture to help the plants germinate faster. If you do not have a dome to cover your seedlings, you can substitute a small plastic bag. Remove the plastic when the plants grow tall enough to touch the top of the plastic.
Planting and Light
Plant each seed in an individual container or cell. The seed packets should have a set of instructions as to how deep to plant the seed; otherwise, plant the seed at a depth equal to twice the seed's diameter, advises Texas A&M Extension. Cover the seeds with soil and place the plastic over the top. Water the containers from the bottom by placing them in a tray of water. The soil will pull the water up to the seed through wicking action.
To germinate and grow the seedlings, place them under a fluorescent lamp that is between 2 and 4 inches above the soil on a heating pad. Seeds typically germinate and grow well at 72 degrees F.