Seedy Business: Growing Plants From Seed
In cartoons, people throw a few seeds down on the ground and seconds later a field of flowers appears. In reality, growing plants from seeds is somewhat more complicated, but the average gardener can do it successfully.
"No one knows when humans first started propagating plants, but seeds are a great way to do it," says Robert Berghage, assistant professor of horticulture at Penn State's College of Agricultural Sciences. "Seeds can survive cold, drought and any generally nasty condition you can think of."
To grow a plant from seed, gardeners need a viable (living) seed and an appropriate environment. Beyond being "viable," a seed must not be dormant. "Dormancy is caused by physical or chemical barriers to germination," he says.
Physical barriers. Some plants have hard, waxy seed coats that are nearly waterproof. Berghage recommends cracking the seed coat by lightly scraping the seed with sandpaper.
Chemical barriers. Some seeds may need a cool, moist period in order to break down substances that keep the seed from germinating. "Many gardeners place seeds within a moist paper towel in a plastic bag, which is then stored in the refrigerator," Berghage explains.
The two most important elements in providing an appropriate environment are moisture and temperature.
Moisture. Seeds will become dormant if they dry out. "Too much water also is very bad for seeds because the water doesn't allow the germinating seed to get oxygen," Berghage says. "A quality potting soil can help in avoiding dryness or over-saturation."
Temperature. Each seed has an optimum temperature for germination. For many garden annuals a temperature between 70 and 75 degrees Fahrenheit is best. For cool season plants, such as pansies, 62 to 68 degrees F is best.
"Once your plants have germinated, always provide them with enough light for good growth," Berghage says.
Berghage says a fungal plant disease called "damping off" can cause problems in the early stages of growth. Chemical fungicides can be used to prevent the disease, but Berghage says the following steps can help avoid damping off:
- Use sterile soil and pots.
- Provide good air movement around the plants and soil.
- Allow the potting soil to dry between waterings.