Starting Plants from Seeds – There is a Right Time

Many people have gotten into the trend of growing their own plants for the vegetable garden. The reasons for this are numerous, but some of the more common reasons are: the vegetable variety is not available locally, the vegetable variety is available but is not organically certified, or simply, many people just enjoy jump starting the spring garden season indoors. A common mistake when starting plants indoors is planting the seeds too early, resulting in thin and spindly transplants. To avoid this common mistake, there are a couple of simple rules to follow when starting vegetable plants indoors.

• Determine when you want to plant the transplants outdoors and work backwards from the calendar. To do this you need to know when the last spring frost occurs in your area. In Door County the last spring frost occurs typically on May 10.

• A general rule of thumb is that peppers take eight weeks, tomatoes take six weeks, and cruciferous vegetables (broccoli, Brussels sprouts, cabbage, and cauliflower) take four weeks from seed to transplants.

• Transplants grown indoors should not be planted directly into the garden without “hardening” them off. Plants grown indoors in relatively low light have a very thin layer of wax on the leaf and stem surfaces. This thin layer of wax will not protect the plant from the sun or wind outdoors. A simple way to harden off transplants is to place them in a cold frame. If a cold frame is used, be sure to vent the cold frame on warm sunny days. If you don’t have a cold frame slowly introduce the plants to the outdoors by setting them outside in an area protected from the wind and full sun. Then introduce the plants to more sunlight over time. Transplants should be hardened off outdoors for a period of at least two weeks before planting in the garden.

• Warm season crops such as tomatoes, peppers, and eggplants do not grow well when soil and air temperatures are below 50° F. So even though the last spring frost usually occurs on May 10, do not plan to plant your warm season crops in the garden at that time. Instead think about having your warm season transplants ready to go outside in the cold frame at this time. Then consider planting these crops in the garden around June 1.

• Unlike warm season crops, cool season crops can tolerate light frosts or temperatures that dip below freezing. These cool season crops such as broccoli, cabbage, kohlrabi, and onions are typically planted in early spring to take advantage of the cool spring temperatures. Cool season crops grown as transplants should also be hardened off. Some cool season crops perform best when planted in mid-summer, crops such as Chinese cabbage, Collards, and Kales. The flavor of these crops improves after the plants have experienced light frosts through the fall season.

The objective of starting plants indoors is to get a jump on the season and reduce the time period until harvest. However, many garden crops perform better if direct seeded into the garden. Some cool season crops that are best direct seeded into the garden are: beet, carrot, chard, lettuce, parsnip, pea, potato, radish, spinach, and turnip. Some warm season crops that are best direct seeded into the garden are: bean, corn, and traditional vine crops such as muskmelon, cucumber, summer and winter squash, and watermelon.

The planting guide gives you a general guideline for when to plant seeds for transplants or direct seeding in the garden of many of the traditional garden vegetables. However, do not be afraid to push the limit of the growing season. I have planted these cool season crops (lettuce, radishes, spinach, and arugula) from seed directly in the garden as early as April 15. Push the limits of the growing season and often you will reap the rewards of an early bountiful spring salad.