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 536hardens into a dense mass that delicate young roots can’t penetrate.
Make your own seed-starting mix by combining one part vermiculite or perlite with one part peat moss, milled sphagnum moss, coir, or well-screened compost. Or, buy bagged seed-starting mix. Let your seedlings grow in such a mixture until they develop their first true leaves, and then transplant into a nutrient-rich potting mix (be sure the mix you choose is labeled organic, or check the list of ingredients, and avoid mixes that contain added synthetic fertilizer). To make your own potting mix, combine equal parts compost and vermiculite. For more recipes for mixes, see the Houseplants entry. For safe handling instructions for seed-starting and potting mixes, see the Container Gardening entry.
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 premoistened 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:
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.