Starting seeds indoors gives your vegetable and ornamental plants a chance to grow strong before the gardening season officially commences. Most warm-weather plants can be started indoors in individual seed pots or planting flats. The extra growing times allows them to go into the garden stronger and larger than if they were seeded outdoors later in the spring. Plant most seeds indoors for outdoor transplanting four to eight weeks before the recommended outdoor planting time.
Fill growing containers with a quality soil mixture. Choose a sterilized mix that doesn't have large pieces of bark or other organic matter in it.
Prepare seeds for planting. Nick the seed coat of hard-shelled seeds such as morning glory with a file before planting, or soak in warm water overnight.
Sow two seeds per pot or space seeds 2 inches apart in flats. Sow to a depth twice their width and sow small seeds directly on the soil surface and cover with 1/8 inch of soil.
Moisten the soil then cover the pots with a plastic bag. Place in a warm room to germinate. Germination time varies by plant but is usually between seven and 21 days.
Remove the plastic once sprouts appear. Move the plants to a warm, sunny window for six hours a day or place under grow lights for 12 hours a day. Keep the soil moist but not soggy, watering as necessary.
Thin the seedlings once they grow in their second set of leaves. Pluck out the weaker seedling in pots and thin seedlings in flats so they are 3 to 4 inches apart in rows 2 inches apart.
Transplant outside once all danger of frost passes in spring. Acclimate seedlings to the outdoors over the course of one to two weeks by placing them outside for a few hours each day and gradually increasing the time until they spend an entire day outside.