In spring, some gardeners think about getting a head start indoors with their vegetable plants by seed germination, but the results can be a disaster if basic principles are not followed. Well-drained and sterile commercial bagged potting soils will eliminate two serious problems for the indoor gardener who wants to germinate seeds – overwatering and disease.
Never try to germinate seeds in garden soil unless you take the time and trouble to pasteurize it first. And even then, the physical properties of soil in a container are not ideal for indoor seed germination. All containers for germinating seeds need drain holes to carry off the extra water.
The container should be deep enough to hold a good supply of material. Shallow containers, such as egg trays, don’t hold enough material for strong root growth and they tend to dry quickly. Select containers that are 3 to 4 inches deep.
Commercial potting soil is often difficult to wet. After you put it in the container, water several times per day before you actually sow the seed. Water passing through the drain hole is a good indication of moisture content, but doublecheck by digging into several containers to see if all the material is saturated. With good drainage, there is no danger of overwatering.
Once you have sown the seeds in the mixture, place a plastic bag over the container to retain moisture. Directions often suggest placing the container in a bright location next to a window. However, the seedling container may get too cold for optimum germination near a window, particularly at night. Nearly all garden seeds need a minimum temperature of 70 degrees F. both day and night until the seedlings are up and well established.
Pepper, eggplant and tomato seeds require temperatures as much as 10 degrees higher for good seed germination. Vine crops like cucumber, muskmelon, squash and watermelon germinate very well at temperatures close to 95 degrees F. Cool germination temperature probably accounts for most germination failures.
As soon as the seeds have germinated, your young plants will need plenty of light. Use fluorescent lights to produce strong growth. Two 40-watt daylight lamps are a good starting point.
Don’t underestimate the time it takes to produce quality transplants. Most seed will germinate and break through the surface of the medium in about a week. However, eggplant, pepper and tomato seed may take up to two weeks to germinate. In addition to the germination time, it can take from six to seven weeks to produce a strong seedling that is ready for the garden. If you wish to start vine crops indoors, these seedlings can be ready to plant out in as little as three weeks.
In some areas, animals feed on newly planted seeds, which means that you must use strong seedlings. Chipmunks can be a serious pest to vine crop, pea and bean seeds.
The exact time to set transplants will depend on your frost free date, or how willing you are to use effective frost protection to fool Mother Nature in spring.