by Erin LaFaive, Horticulture Educator, Eau Claire County UW Cooperative Extension
Do you want to get ahead of the growing season? Do you want to plant vegetables that need a longer growing season? Do you want to grow a plant that you can’t find in the stores? A solution to these challenges is to start your own seeds indoors.
Many plants do better if started indoors, since it gives them a jump start on the growing season. This is especially the case in northern Wisconsin where the growing season is shorter and some seeds have a difficult time germinating in the early season. Tomatoes and peppers are a great example of plants that need longer growing seasons than northern Wisconsin can provide.
Containers Any type of container can be used to start seeds as long as it is sterilized before planting and has drainage holes at the bottom. To sterilize pots, soak the containers in a 10 percent bleach mixture and thoroughly rinse. Single celled pots are sold in stores and generally only a seed or two are planted in one cell. Mass-sowing seeds are done in flats that do not have dividers and they require transplanting after the seedling is bigger.
Soil Use a seed starting mix or other soil-less indoor plant mixture. These types of soils have been sterilized and contain smaller particles so the embryos have an easier time pushing through. In addition, they are light weight and drain well. If you want to create your own mixture use a pasteurized mixture of equal amounts of soil, sand, vermiculite or perlite; and peat moss.
Planting Moisten the soil before you add it to the containers. It shouldn’t be soggy. The general rule for planting depth is four times the thickness of the seed. Also, check the seed packet for recommendations. Some seeds are very small and hard to see. In those cases, mixing the seed in sterile sand can help you see where you are spreading the seed. Very small seeds are simply sprinkled over the top of the soil. To cover seeds use vermiculite or a layer of screened potting mix you are already using over the seeds. Leave about a ¼ of an inch from the top of the container to allow enough room for the vermiculite.
Germination Cover the planted seeds with plastic leaving an inch to an inch and a half gap. The plastic helps to keep the soil from drying out and traps some heat. A heating source underneath the seeds will speed up germination. Place them in a window with moderate light but not in direct sunlight. The temperatures should be 55 to 60 degrees Fahrenheit at night and 65 to 70 degrees Fahrenheit during the day.
Watering Keep the soil moist, but be careful not to overwater. Using a spray bottle works great for tiny seeds because a strong stream of water may move the seeds around too much. Even a stream being poured from a glass of water can be too strong. Watch for the growth of mold which generally looks like white fuzz on the soil surface. When the first seedlings appear, take off the plastic. This is also the time they need stronger light so they require a south facing window or artificial lights.
My plants are lopsided! My plants are spindly! This can be prevented by turning the container as the seedlings grow and by giving enough light. Fluorescent lights are another source of lighting. They need 16-18 hours of light. One warm-white, 40-watt bulb and one cool-white, 40-watt bulb used together are adequate for seed starting and seedling growth. You can also use fluorescent lights or grow lights.
Gradually acquaint the seedlings to outside by first starting with an hour and working up. The seedlings are not use to fluctuating temperatures, wind, and the sun and this gradual introduction prepares the plant for new conditions.
These are general indoor seed germinating rules. By reading the seed package you will likely find more detailed information on seed depth, germination time, and any other specialized requirements.