Starting seeds indoors will give you earlier vegetables and flowers, and your cultivar choices will be endless. The process of germination may seem complex, but the act of seed planting is reassuringly simple. Just take it step-by-step, and you’ll soon be presiding over a healthy crop of seedlings.
Select your work area—a surface at a comfortable height and close to a water supply where you’ll have room to spread things out. Assemble your equipment: seed-starting containers, starting medium or soil mix, watering can, labels, marking pen, and seed packets.
You can start seeds in almost any kind of container that will hold 1 to 2 inches of starting medium and won’t become easily waterlogged. Once seedlings form more roots and develop their true leaves, though, they grow best in containers that provide more space for root growth and have holes for drainage.
You can start seedlings in open flats, in individual sections of a market pack, or in pots. Individual containers are preferable, because the less you disturb tender roots, the better. Some containers, such as peat pots, paper pots, and soil blocks, go right into the garden with the plant during transplanting. Other pots must be slipped off the root ball before planting.
Square or rectangular containers make better use of space and provide more root area than round ones do. However, individual containers dry out faster than open flats. Many gardeners start seeds in open flats and transplant seedlings to individual containers after the first true leaves unfold. Choose flats and containers to match the number and types of plants you wish to grow and the space you have available.
Newspaper pots are perhaps the simplest DIY seed-starting containers. To make pots from newspaper, begin by cutting bands of newspaper about twice as wide as the desired height of a pot (about 4 inches wide for a 2-inch-high pot). Wrap a band around the lower half of a jar a few times, and secure it with masking tape. Then form the bottom of the pot by creasing and folding the paper in around the bottom of the jar. You can also put a piece of tape across the pot bottom to hold it more securely in place. Slip the newspaper pot off the jar. Set your pots in high-sided trays with their sides touching. When you fill them with potting mix, they will support one another. There are also commercial molds for making newspaper pots.
Seed-Starting and Potting Mixes
Seeds contain enough nutrients to nourish themselves through sprouting, so a seed-starting mix does not have to contain nutrients. It should be free of weed seeds and toxic substances, hold moisture well, and provide plenty of air spaces. Don’t use plain garden soil to start seedlings; it hardens into a dense mass that delicate young roots can’t penetrate.
Some gardeners prefer to plant seeds directly in potting mix and eliminate transplanting. Planting in large individual pots is ideal for plants such as squash and melons that won’t grow well if their roots are disturbed.
Moisten the planting mix before you fill your containers, especially if it contains peat moss or milled sphagnum moss. Use warm water, and allow the mix time to absorb it. When you squeeze a handful of mix it should hold together and feel moist, but it shouldn't drip.
If you’re sowing directly in flats, first line the bottom with a sheet of newspaper to keep soil from washing out. Scoop pre-moistened planting medium into the containers or flats, and spread it out. Tap the filled container on your work surface to settle the medium, and smooth the surface with your hand. Don’t pack it down tightly.
Space large seeds at least 1 inch apart, planting 2 or 3 seeds in each pot (snip off the weaker seedlings later). Plant medium-sized seeds ½ to 1 inch apart, and tiny ones about ½ inch apart. If you’re sowing only a few seeds, use your fingertips or tweezers to place them precisely. To sprinkle seeds evenly, try one of these methods:
- Take a pinch of seeds between your thumb and forefinger and slowly rotate thumb against finger—try to release the seeds gradually while moving your hand over the container.
- Scatter seeds from a spoon.
- Sow seeds directly from the corner of the packet by tapping the packet gently to make the seeds drop out one by one.
- Mix fine seeds with dry sand, and scatter the mixture from a saltshaker.
To sow seeds in tiny furrows or rows, just make shallow ¼- to ½-inch-deep depressions in the soil with a plant label or an old pencil. Space the seeds along the bottom of the furrow.
Cover the seeds to a depth of three times their thickness by carefully sprinkling them with light, dry potting soil or seed-starting medium. Don’t cover seeds that need light to germinate (check the seed packet for special germination requirements). Instead, gently pat the surface of the mix so the seeds and mix have good contact.
Write a label for each kind of seed you plant and put it in the flat or pot as soon as the seeds are planted, before any mix-ups occur.
Set the flats or pots in shallow containers of water and let them soak until the surface of the planting medium looks moist. Or you can gently mist the mix. If you water from the top, use a watering can with a rose nozzle to get a gentle stream that won’t wash the seeds out of place.
Cover the container, using clear plastic or a floating row cover for seeds that need light, or black plastic, damp newspaper, or burlap for those that prefer the dark.
Finally, put the containers of planted seeds in a warm place where you can check them daily. Unless the seeds need light to germinate, you can save space the first few days by stacking flats. Just be sure the bottom of a flat doesn't actually rest on the planting mix of the flat below. Check the flats daily; unstack as soon as the seeds start to sprout. Keep the soil moist but not waterlogged. As soon as you notice sprouts nudging above the soil surface, expose the flat to light.
To plan the best time to start seedlings indoors in spring, you need to know the approximate date of the average last spring frost in your area. Count back from that date the number of weeks indicated below to determine the appropriate starting date for various crops. An asterisk (*) indicates a cold-hardy plant that can be set out 4 to 6 weeks before the last frost.
- 12 to 14 weeks: onions*, leeks*, chives*, pansies*, impatiens, and coleus
- 8 to 12 weeks: peppers, lettuce*, cabbage-family crops*, petunias, snapdragons*, alyssum*, and other hardy annual flowers
- 6 to 8 weeks: eggplants, tomatoes
- 5 to 6 weeks: zinnias, cockscombs (Celosia spp.), marigolds, other tender annuals
- 2 to 4 weeks: cucumbers, melons, okra, pumpkins, squash