Successful Seed Germination
by Sherry Rindels, Department of Horticulture, Horticulture and Home Pest News, and Iowa State University Extension and Outreach
A seed is a miracle waiting to happen. The embryo comes pre-packaged with a food supply and the vital genetic information needed to become a plant just like its parents. Seeds exist in a state of dormancy, absorbing oxygen, giving off carbon dioxide, and slowly using up their stored food reserves. During this process the seed continually monitors the external environment waiting for ideal conditions specific for the particular seed. Once the ideal conditions occur, the seed breaks dormancy and germinates. The seedling gathers energy through its leaves by the process of photosynthesis and absorbs nutrients and water from the soil through the roots. As gardeners, our goal is to provide the optimal environment for germination and seedling growth.
For germinating seeds indoors, select a well-drained potting medium designed specifically for germinating seeds. Use clean containers with drainage holes in the bottom. Wash used containers with warm soapy water and rinse with a dilute bleach solution (1 part bleach to 9 parts water). Slightly overfill containers with the potting soil and tap the bottom and sides to encourage even settling.
Create a level surface by scraping excess soil with a board or knife. Do not press or compact the soil which will make it harder for the seeds to get started. Some gardeners will lightly firm the soil with a board to create a level surface. Moisten the soil either by watering carefully from the top or letting water soak up through the bottom. Allow excess water to drain away.
Seeds require a certain temperature in order to germinate. Each plant has a specific optimum and a range within which germination will occur. The closer the temperature is to optimum the quicker germination will occur. Most seeds germinate when the soil temperature is between 68(and 86(F. Once germination occurs, the optimum growing temperature for theseedling is about 10(F cooler than the optimum germination temperature.
Moisture is critical for germinating seeds. They like a moist but not soggy environment. Seeds require oxygen and if kept in a waterlogged state may rot. On the other hand, if the soil dries out, the seed will lose whatever water it has absorbed and will die. Finding the middle ground can be difficult and comes easier with practice. After sowing the seeds, mist the tray with water and cover with plastic wrap, a plastic bag, glass or plexiglass to seal in moisture. As soon as seed germinates remove the covering. Check the seedlings twice a day for moisture. Allow the soil surface to dry between waterings. Ventilation and air circulation are also important to discourage damping off diseases. Some seeds need light in order to germinate, but many do not. Seed packages will usually indicate what your particular selection requires. It is important to follow the directions given on the package for planting depth. In addition to light requirements, seeds that are planted too deep will not have enough stored energy to reach the soil surface and may die in the process. After germination occurs, seedlings require about 12 to 16 hours of light a day. Intense light is necessary to prevent spindly or leggy seedlings. If you are growing under lights, make sure the light source is 4 to 6 inches above the plants. In a sunny window, turn the seedlings regularly to avoid leaning.
If you are sowing seeds in furrows or flats, transplant individual seedlings into cell packs when the first true leaves appear or when they are large enough to handle Seedlings started indoors should be fertilized regularly with a dilute (1/4 strength) water soluble fertilizer. This will help to produce stockier transplants provided enough light is available.
Before planting in the garden, gradually acclimate transplants to the outdoors. Start by putting them outside on cloudy days or in a shaded location then after a few days work them into more light and exposure. Overcast skies or late afternoon is the best time to plant in the garden. Water immediately after transplanting. If plants wilt, provide some protection with an open milk carton or a board for a few days.
As gardeners everywhere begin the gardening season, these suggestions should help in raising strong healthy plants for enjoyment in the months to come.
This article originally appeared in the February 9, 1996 issue, p. 11.
February 9, 1996