There are a few basic steps to starting most types of seeds indoors before they turn into seedlings that are ready to be planted outdoors:
- Choose the right container to start off the seeds.
- Select the right spot with enough light for seeds to germinate and augment the space with grow lights and a heat mat if necessary.
- Keep seeds moist, but not too wet.
- Gently prepare seedlings for the outdoors by hardening them off if you plan.
- "start indoors eight weeks before last expected frost date in your area." A simple internet search will tell you the date of the expected last frost in your area. Count backwards to, for example, eight weeks before that, and that's the date you should start your seeds.
- Planting time: Most seed packets will tell you quite clearly if the seeds can or should be started indoors. For some species (tomatoes, for example), it is virtually mandatory to start seeds indoors in cold-weather climates. For other species it may be optional, and for other fast-growing species, there may be no indoor starting information at all—these plants are best planted directly in the outdoor garden.
- Days to maturity: This will tell you how long the plants take to produce edible fruit or ornamental flowers. Some tomato plants take as much as 100 days to reach fruit-producing maturity. If you want tomatoes in July, this means the seeds need to be started in early April.
- Light and water needs: The seed package will tell you if the seeds need lots of light. If so, starting them indoors may require a fluorescent grow light—or you may need to reserve your sunniest window for seed-starting.
- Soil needs: Some seeds can be started in ordinary potting soil, while others require a porous, fine-grained seed-starting mix. The package may also suggest an optimal soil temperature for seeds to germinate. Seeds that require 70-degree soil to germinate will clearly need to be started indoors in cold-weather climates since the soil does not get adequately warm until late into May.