A great way to get a head start on growing your veggies is to start seeds indoors. Many plants fare better when they are started indoors and later transplanted as seedlings, though it is not recommended for all vegetables (root vegetables, corn, peas, and beans). For spring planting, the seeds that should be started indoors include tomatoes, peppers, eggplant, cucumber, and squash. During the fall, vegetables such as broccoli, cabbage, and cauliflower should be started indoors.
When to Start
Many seed packets will have planting instructions and include when to start indoors. It varies from seed to seed, where you are located, and the season. Here is a handy chart on when to start seeds indoors as well as when to transplant during the spring. For spring vegetables such as peppers and tomatoes, they should be started 6 to 8 weeks before the last frost date. Fall vegetables such as broccoli and cabbage should be started 12 to 14 weeks before the first frost date. If you don’t know the frost date for your area, please refer to this chart.
Containers and Growing Medium
Most nurseries sell seed starting kits and containers, but you can really use any small container to start seeds in. We have used dixie cups, yogurt cups, egg cartons, and even eggshells. Whatever container you use, make sure it drains water well and is clean. To save money and time, purchase your supplies online (we like Greenhouse Megastore) and reuse them year after year. When starting our seeds, we first plant them in 72 cell propagation trays. When the seedlings are large enough, we transplant them from propagation trays into larger pots (see “Potting Up” below), then into the garden when the time is right.
You can buy bags of seed starting medium or you can make your own. We mix together half potting soil and half compost along with a few handfuls of Perlite. Since seedlings are very susceptible to disease, make sure the medium you use is sterile.
When you first plant your seeds, they need to be kept in a warm, moist environment to facilitate germination. We keep the trays covered with plastic to help hold in the heat and moisture. The best soil temperature for germination varies from seed to seed and ranges from 65 to 85 degrees Fahrenheit. We use a warming mat and try to keep the soil temperature around 75 degrees. During this time, the growing medium needs to stay moist, but not water logged.
Once the seeds germinate, the plastic cover needs to be removed and the lights turned on. We also remove the heating pad since seedlings require less warmth to grow. If you have a very well lit windowsill, you can use that for a light source. We use fluorescent daylight bulbs that have a color temperature of 6500K. Seedlings generally require 14 to 16 hours of light per day. The lights should be consistently kept about 2 inches above the seedling. As they grow taller, the lights need to be raised up. If the lights are too far away when they first germinate, the seedlings will develop long and leggy stems and will not be as strong for transplanting.
Potting Up and Transplanting
Potting up involves transplanting your small seedling into a larger container that continues to grow indoors. Sometimes this may not be required if you started your seedling in large enough containers to begin with. Potting up gives your seedling more room to develop the root system and has been shown to stimulate plant growth. The small cells in our propagation trays, which have 3 cubic inches of growing room, do not provide enough root growing space. Once the seedlings develop their second set of true leaves, we transplant them to larger pots with 10 cubic inches of space. Some growers do this 2 to 3 times into larger and larger pots before they transplant into the garden. We usually only do it once, though it depends on how large the seedlings get and the timing for transplanting.
Once the seedlings have sufficiently grown, use this planting chart to determine the best day to transplant into the garden. Before transplanting, be sure to harden off the seedlings by slowly exposing them to the outdoor elements. This acclimates the seedlings to their new environment making them more likely to survive transplantation.