Though we haven’t quite escaped the risk of frost, some cool-season flowers such as pansies, calendulas and snapdragons and vegetables including beets, spinach and kale are ready to be seeded in the ground. More fragile plants can be started indoors in anticipation of the impending growing season. Follow these tips for a successful crop of seedlings and get your garden started right.
As with growing in the ground, beginning with healthy soil is essential. To establish seeds, the soil must be loose to allow proper drainage. Of equal importance is ensuring the soil is free from diseases. This means that recycled soil should be sterilized. Another option is to begin with fresh soil which you can mix yourself or purchase prepackaged. Using healthy soil from the start minimizes the risk of diseases such as damping off which is more common in already unhealthy seedlings. Ensure the containers used for seed starting are also sanitized prior to planting.
Some plant varieties, such as poppies (Papaver sp.), and sweet peas (Lathyrus odoratus), have more fragile roots and don’t handle being transplanted well. In these cases, peat pots are a good option for planting. Peat pots are biodegradable. They allow adequate drainage and can be planted directly into the ground when the seedlings are ready. This prevents the roots from being damaged.
If you have ever started seeds indoors you may be familiar with the struggle to provide adequate light. While some plant varieties, such as lettuce and other leafy greens, can do well with the light provided in a bright window, other varieties will not. Seedlings that don’t receive enough light can become elongated and will flop over to the ground when transplanted. To overcome this problem fluorescent lights can be used to provide supplemental lighting for 14 to 16 hours each day. Monitor the seedlings as they grow and raise the lamps as needed to avoid burning the leaves.
Another reason you may notice seedlings growing leggy stems is due to temperatures getting too high. Keep the temperature in the growing area between 60- and 65-degrees Fahrenheit during the night and up to 70 degrees during the day. Keep the soil moist but never in standing water.
Soilless mixes have little, if any, fertilizer so for best growth apply a houseplant fertilizer at half-strength to the seedlings one week after germination. Continue the fertilizer regimen according to the package instructions as the seedlings grow.
Seedlings will be ready to transplant when the first set of true leaves have matured. True leaves are the ones which develop after the cotyledons (primary leaves). They have the same shape as the adult leaves though they will likely be smaller. At this point in the spring, it is likely still too soon to plant outdoors so seedlings can be transplanted into larger containers and continue to grow indoors. Dig up the seedlings with caution to avoid tearing roots. As you replant keep the seedlings at the same soil depth. If the seedlings were grown in peat pots, thin them out so there is only one plant per container.
Most of the seedlings will be ready to be moved outdoors within four to six weeks. Time your seed starting to account for the weather. The move outside will need to be done gradually to avoid causing shock to the plants. Seed starting indoors can be a fun and more affordable way to begin the garden season.
Cynthia Domenghini is an instructor and coordinator for K-State’s horticultural therapy online certificate program.