Harvesting Wildflower Seeds
By: Eve Pranis
Since fall is when many wild plants release their seeds, it's a good time to explore wild plants' seed dispersal strategies, collect them for you classroom garden, and experiment with methods of inducing them to grow. You'll have the best chance of success if you harvest seeds when they're ripe. Most of the wild plant seeds you collect will be mature or ripe 4 to 6 weeks after they've flowered. Have your eagle-eyed scientists carefully observe flowers in your area, looking for a change in fruit color from green to brown or black and a sign that the typically dark, firm, and dry seeds are ready to disperse.
Never collect seeds of any plant that seems to be in short supply in a given area ore that you know to be endangered. Leave plenty of seeds so that the plant can continue to produce new generations. If you're not planting seeds right away, dry them in an area with good circulation for a couple of weeks and store them in an airtight container in a refrigerator or other cool, dry place.
Coaxing Germination Indoors
Although they're billed as hardy survivors, wildflower seeds can be challenge to germinate in your seemingly cozy classroom setting. Most wildflowers from cold climates require a dormant period of cold winter-like temperatures followed by spring-like warmth to germinate. This adaptation prevents them from germinating in the fall when subsequent winter conditions would prevent their surviving.
Your students may want to experiment with some of the following seed treatments to encourage seeds from wild plants to germinate in the classroom:
Scarring. Some seeds with hard coats will germinate more successfully if you use a file a sandpaper to scar the seed coat, taking care not to go deeply enough to injure the embryo. Invite your students to examine why scarring aids germination by looking at a bean seed and noticing the tiny opening near the scar where it was attached to the pod. This is the micropyle through which water enters. Try painting over the micropyle on one seed with nail polish, leaving one seed alone, and scarring a third seed. Soak them all in water, make predictions about how they'll look in a day, then compare them.
Soaking in hot water. Some seeds with hard coats, such as lupines, do best when placed in boiling water and then left to soak in the cooling water overnight before planting.
Moist chilling or stratification. Many seeds dispersed in the fall have internal dormancy, requiring a period of cold before they'll germinate. Consider putting seeds in a bit of damp peat moss, vermiculite, sand or potting mix in a plastic back or jar. Keep them in the refrigerator for 2 to 3 months before removing and planting.