Growing plants from seeds pictured on bright packets is great fun, but have you considered the potential for excitement and discovery in collecting and planting unknown treasures from the meadows, overgrown lots, or woods in your school environment? Fall is the time when many trees, shrubs and wild plants release their seeds -- making it a good time to explore their many dispersal strategies and collect them for planting in your classroom garden.
To increase your chances for successful germination, it helps to first think about the needs and adaptations of seeds in the wild. Although some seeds produced during the summer or fall will germinate as soon as they disperse from their parent plant, think about the implications, particularly in colder climates, of this behavior. If seeds of plants that thrive during the warmer growing season were to germinate when they fell to ground in the fall, the seedlings would likely be killed by the cold winter temperatures.
Seeds of many wild plants have adaptations that ensure dormancy until conditions are right for successful germination. Many actually require a period of cold (winter) temperatures followed by (spring) warmth, to germinate. Some seeds have hard seed coats which, during alternate freezing and thawing conditions, will soften up and germinate. You can simulate both of these conditions...but first, you'll need to collect seeds.
Most of the wild plant seeds you collect will be mature or ripe about 4 to 6 weeks after they've flowered. You'll have the best chance of success if you harvest seeds when they're ripe. A change in fruit color (from green to brown or black), and a sign that they're ready to disperse are indicators that they're mature.
To collect seeds from cone-bearing trees, harvest cones before they've opened all the way. Put each cone in a plastic bag and place it in a warm spot until the seeds can be shaken loose.
Have your students keep careful records about the growing conditions of the plants from which you collect seeds, so they can plant them in the spring. Is it sunny? Shady? A wooded area? An open field? Also predict the springtime conditions in each location.
Never collect seeds of any plant that seems to be in short supply in a given area. Ensure that there are plenty to continue producing seeds for new generations
If you're not planting the seeds or giving them a cold treatment right away, dry them in an area with good circulation for several weeks and store them in a refrigerator or other cool, dry place.
Some seeds require no special treatment, and others may require one or more treatments to break dormancy. Before experimenting with different seed treatments, consider simply soaking the seeds overnight and placing them on moist paper towels in a plastic bag. They may germinate with no additional treatment.
Consider experimenting with the following treatments:
In all cases, keep seeds in the refrigerator for one to four months before removing and planting. Check from time to time to make sure the mixture remains moist.
One of the most common problems in planting wild seeds is planting too deeply. Tree seeds should be planted about 3X as deep as the seed diameter; wildflowers about 1X as deep as the diameter; very fine wildflower seeds and grass seeds should be gently pressed into the soil without being covered.
Some require light to germinate, some require dark, and others will germinate with either. You might want to experiment with several different light conditions.
To grow to maturity, most wild plants require cooler nighttime temperatures than are likely found in your school. After two to four months of growing indoors (or when springtime arrives!) you should transplant them outdoors.