A greenhouse is one of the easiest ways to start seedlings and helps a gardener grow as they please with no regard to the weather. Utilizing this grow method is also one of the least expensive ways to start seedlings, although there is an investment in starting or building a greenhouse. But even a small greenhouse with a 3-by-10-foot plot can provide up to 100 heads of lettuce. Hundreds of different flowers, plants, fruits, vegetables and herbs can grow in a greenhouse successfully, but the method of growing each will vary in one way or another. When growing plants in a greenhouse, start from seedlings and make sure the soil and environment are prepared properly.
Set the environment of your greenhouse to make sure you can control the heat (with a passive or active system) and circulation system. Passive systems like water storage tanks use the sun's energy to heat the greenhouse at night, while active systems require a source of energy like gas or electrical. Using the right heating system for your specific greenhouse depends on the size, your climate and the variety of plants you grow.
Establish the circulation system to prevent disease and mold by using windows or ventilation intakes and exhausts. This shouldn't take up more than around 25 percent of the total surface if you establish them yourself.
Fill the flats or seed boxes with a good-quality potting soil. Sow the seeds in the soil, pushing them as deep or lightly as the seed variety requires. Place the flats in a 1-inch layer of water to soak through the drainage holes. Remove the flat once you see the moisture reach the soil's top.
Keep the plant seeds in a warm area for up to two weeks. Water when the soil feels dry on top.
Transplant your seedlings when they are about 2 inches tall to deeper flats, or even small planter pots. The day before you transplant, water the seedlings. Transplant only the strong, healthy seedlings, carefully pulling them up from the soil with your fingers. Create a small hole in the new flat with your finger, and put the seedling in it. Soak the flat immediately and continue providing full sun and watering care as when the plants were seedlings.
Repeat this process as the plant grows and needs a larger pot. Water and fertilize for each specific plant's needs.