Penn State News

04-03-2000
Generally about this time of year we think of starting vegetable plants indoors but this often turns into disaster if basic principles are not followed.

The availability of well-drained and sterile commercial bagged potting soils will eliminate two serious problems for the indoor gardener -- over-watering and disease. Commercial mixes are sterile and they drain well. 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 used to germinate seeds will need drain holes to carry off 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 it is placed in the container water it several times the day before you actually sow any seed. Water passing though the drain hole is a good indication of moisture content, but also dig into several containers to see if all the material is saturated. With good drain holes in the container, there is no danger of over-watering.

Once the seeds have been sown in the mixture, the container is placed in a plastic bag to retain moisture. Directions often suggest placing the container in a bright location next to a window. In such a location the seedling container may get too cool for optimum germination. Particularly at night, a container set next to a window may get much colder than you realize.

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 germination. Vine crops like cucumber, muskmelon, squash and watermelon germinate very well at temperatures close to 95 degrees F. Cool germination temperature is probably to greatest cause for failure for many gardeners.

As soon as the seed have germinated your young plants will need plenty of light. Use fluorescent lights to produce better growth. Two 40-watt daylight lamps are a good starting point. To prevent the plants from getting weak and spindly keep the light about 6 inches above the tops of the plants. Leaves the light on for 14 to 16 hours a day.

Don't under estimate the time needed to produce quality transplants for the garden. 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 2 weeks to germinate. In addition to the germination time it can take from 6 to 7 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 3 weeks. In some areas, animals feeding on direct planted seeds necessitates that you use strong seedlings. Chipmunks can be a serious pest on seeds of vine crops, peas, and beans.

The exact time to set transplants will depend on your frost-free date, or how willing you are to use effective frost protection measures to fool Mother Nature this spring.

**Dr. Robert Nuss is a horticulturist at Penn State. He coordinates all extension horticulture programs. He has bachelor’s, master’s, and doctoral degrees in ornamental horticulture and has been on the Penn State faculty since 1966.