SEED STARTING by Steve Rozic

Containers

You can start seeds in almost any kind of container that will hold 1 to 2 inches of starting medium without becoming waterlogged. After seedlings form more roots and develop leaves, though, they grow best in larger individual containers that provide more space for root growth and have holes for drainage.

Flats are large, rectangular containers that hold many seedlings. Many gardeners start their seeds in them, then transplant the seedlings to individual containers after the first true leaves unfold. If you raise lots of seedlings, it’s useful to have interchangeable standard-size flats and inserts. You can buy flats at a garden center, or make your own by constructing a rectangular wooden frame, 3 to 4 inches deep. Nail slats across the bottom, leaving a ¼ inch between them for drainage.

Although individual containers dry out faster than flats, they are better for starting seeds because you don’t have to repot as often, so the seedlings’ tender roots are less likely to be damaged by constant handling. Some containers, such as peat pots go right into the garden with the plant during transplanting so the plants’ roots are never disturbed.

Or you could splurge: Spend a couple of bucks on containers that are designed for starting seeds. Most garden centers and many home and hardware stores carry cell packs, plastic trays that have individual 2 inch-deep pockets with drainage holes. (Leftover “six-pack” containers from the garden center will work fine, remember to wash them thoroughly before using.) These special-purpose packs range from 6 cells to 40 or more, and many include a clear plastic dome that helps maintain humidity until the seeds have sprouted.

Peat pots, made entirely of peat moss, are popular because you can plant them “pot” and all—you don’t have to worry about extracting the seedlings from the containers before you set them in the garden. Also, the peat absorbs excess moisture naturally, so seedlings are less susceptible to damping-off, a fungal disease that often occurs when soil is too soggy. But because peat pots do dry out faster than plastic containers, you’ll need to check their moisture level daily. Also, peat is not a sustainable resource, so the better option is Coconut coir.

No matter what kind of container you start your seeds in, you’ll also need a tray to put beneath the containers. This allows you to water your seedlings by filling the tray rather than dumping water on them from the top. A plastic lid or wrap for covering the containers after you seed them will help keep the seed-starting mix moist and encourage germination. Also be sure to have some simple markers or labels on hand so that you can note the variety and sowing date.

Buying a Seed-Starting Mix:

Seeds contain enough nutrients to nourish themselves, so a seed-starting mix doesn’t have to contain nutrients. But it should provide plenty of air spaces, hold moisture well, and be free of weed seeds and toxic substances. Peat moss, compost, perlite, and milled sphagnum moss—either alone or in combination—are all good materials for starting seeds. Don’t use plain garden soil, though; it hardens into a dense mass that seedling roots can’t penetrate.  When your seedlings have their first set of true leaves (see below), you’ll need to transplant them to a potting mix.

 Lights

Seedlings need more intense light than full-grown plants. If they don’t get 14 to 16 hours of strong light a day, most become spindly and weak. Although many gardeners start their seeds on windowsills, the light from a window during the short days of winter often isn’t enough to grow strong, sturdy seedlings.

Light Advice

A grow-light system will provide seedlings started indoors with enough light to produce healthy, compact transplants for the garden. Here’s how to get the most from your lights:

• Growing seedlings need lots of bright light. Keep the lights on for at least 14 hours a day, and suspend the lights close to seedling leaves.
• Because tubes produce less light at the ends, choose the longest tubes you have room for and rotate seedlings at the ends into the middle every few days.
• Keep the tubes clean. Dust can decrease the amount of light available.
• To increase light from a fluorescent fixture, position a mirror or aluminum foil alongside it to reflect light back onto seedlings.

When you’re ready to transfer seedlings to larger pots, you can use potting soil.

Most seedlings will do better if you grow them beneath fluorescent lights. You can buy expensive grow lights, but the 4-foot-long shop lights sold at hardware stores work just as well and cost much less. Start with new tubes—fluorescent tubes become dimmer over time. Don’t bother with incandescent bulbs. Their light does not stimulate growth well. Suspend your light fixture from the ceiling over a table or bench. To protect the table or bench from water, cover it with a plastic sheet.

Heating Mats

Most seeds—including tomatoes and peppers—germinate much faster in warm soil (about 70° to 75°F). To provide those toasty temps, heating mats come in handy. You just plug them in and set your containers on top of them. Keep in mind that most sprouted seedlings grow better in slightly cooler temps (upper 50s to lower 60s), so remove the heating mat after the seeds have sprouted.

Damping Off – A good seed starting mix strikes a balance between moisture retention and drainage, both of which are necessary for seedlings. “Regulating the moisture is key,” Johnson says. “It’s easy for the soil to stay too wet, and that can lead to damping-off.” Damping-off is a fungal disease that causes newly germinated seedlings to topple over and die.