Sowing seeds in containers

Many plants are best raised from seed sown in containers. These include slow-growing perennials, plants with expensive or very fine seed, and warm-season vegetables and annuals that you want to start when the garden soil is still too cold and wet for in-ground planting.

SOWING SEEDS IN CONTAINERS Many plants get off to a better start when sown in containers and transplanted to garden beds later in the season. These include slow-growing perennials, plants with expensive or very fine seed, and warm-season vegetables and annuals that you want to start when the garden soil is still too cold and wet for in-ground planting. It’s easier to provide plants in containers with the warm temperatures and bright light they need for quick growth, and easier to protect them from insects and birds as well. The seed packet information will help you decide when to plant; most annual flowers and vegetables should be sown 4 to 8 weeks before it’s time to transplant them to the garden. Container choices Convenience, cost, and reusability will determine which containers you use. If you won’t be around to water daily or don’t plan to transplant seedlings into another container before planting them out, use 2- to 4-inch-diameter containers or flats with individual cells. Plastic flats with no dividers are an old favorite. They’re readily available from garden supply stores and mail-order catalogs, and free when you buy seedlings at nurseries. Plastic cell-packs and 2- to 4-inch plastic pots, recycled from nursery purchases, are easy to obtain and use. Peat pots are inexpensive but not reusable. But because you plant out seedlings pot and all, such pots minimize disturbance to roots. Keep them moist (so roots can penetrate them easily). Plastic foam flats with tapered individual cells are sold by nurseries and through seed catalogs. They come in several cell sizes; some have capillary matting that draws water from a reservoir, making seedling care much easier. In addition to the containers listed above, you can use household items ― plastic cups, yogurt containers, cut-down milk cartons, foil baking pans. Be sure to punch several drainage holes in any container that lacks them, since seedlings will die if water collects around their roots. If you’re reusing old pots, scrub them out and soak them for 30 minutes in a solution of 9 parts water to 1 part household bleach to destroy any disease organisms. GROWING MEDIUM Use the seed-starting mixes or potting soil sold at nurseries, or make your own mix by combining 1 part each of peat moss, vermiculite, and perlite. Dampen the mix before using it by pouring it into a clean bucket, then stirring in enough water to make it moist but not soggy. Fill each container to within 1/2 inch of the rim with the damp mix, firming it gently with your fingers, a block of wood, or the base of a jar. Check the seed packet for recommended planting depth. You can make furrows in the containers or scatter the seeds over the surface. If you’re using containers with individual cells, plant two seeds per cell. Cover the seeds with the proper amount of prepared mix, taking care not to cover them too deeply. To prevent later confusion, label each container with the plant name and sowing date. Loosely cover the containers with wet newspaper, damp burlap, or aluminum foil; this helps keep the soil moist but still allows air to get in, preventing the growth of fungus. If the seeds need light to germinate (this will be noted on the packet), gently press them into the potting mix, but do not cover them with more mix. Loosely cover the containers with a sheet of clear plastic. Place the containers in a warm spot. After 3 days, check daily for germination. As soon as you see green leaves arching out of the soil, uncover the containers and move them into bright light (but not direct sunlight): without adequate light, the seedlings will quickly become spindly and weak. If you aren’t using a greenhouse, move the plants to a sunny south window; or give them 12 to 14 hours of fluorescent light per day, setting the lights 6 to 8 inches above the tops of the plants. Water the containers when the surface of the potting mix feels dry. To avoid disturbing the seeds (and, after germination, the roots), spray with a fine mist. Or place the containers in a tray or sink holding a few inches of water; the mix will absorb adequate moisture within a few hours. After the seedlings form their first set of true leaves, fertilize them weekly, using a fertilizer sold for starting seeds or a liquid type diluted to half strength. When the seedlings have developed their second set of true leaves, it’s time to transplant or thin them. Click here for instructions.