As fall weather spells an end to school and neighborhood gardens, consider encouraging your students to become seed detectives by identifying, collecting, and saving their own seeds from the garden or wild.
Saving seeds can be economical (you might generate hundreds from just one plant) and it allows students to explore plant life cycles and their clever adaptations for housing and dispersing seeds. Understanding a few things about seeds and seed needs will improve your chances of being a successful seed saver.
Saving seeds of annual plants may make the most sense for school gardeners, since these complete their life cycle, from seed to seed, in one year. However, you might also want to experiment with saving and replanting seeds from flowers that are biennials (plants that complete their life cycle in two years) or perennials (plants that flower multiple years). This can be an economic way to increase your collection of plants for your garden or for sale. Avoid saving seeds from hybrids, since you can't count on offspring from a hybrid to produce plants like the parent.(Seed catalogs and packets will tell you if seed is hybrid.)
Here are some plants to consider:
Vegetables: beans, peas, lettuce, peppers, pumpkins, squash. (Note: Pumpkins and squash are easily cross-pollinated by insects, which may result in weirdo offspring, but that can be part of the fun!)
Annual flowers: calendula, sweet peas, cosmos, marigolds, sunflowers, four-o-clocks, larkspur, zinnias.
Plants need energy and nutrients to make seeds, and the health of the parent can determine how well the seeds will keep, germinate, and grow. Have your students collect seeds from plants that seem especially healthy and not stressed from drought, disease, or other factors.
The ideal time for gathering seeds varies from crop to crop. Melon seeds, for instance, are mature when the fruits are ready to eat, but squash and cukes should be left on the plant for weeks after you'd normally eat them. Generally, let seeds dry on the plant as long as possible. Have students carefully observe plants to discover at what point the plant would naturally be ready to drop or disperse its seeds.
Typically, seeds are either embedded in pulp or borne fairly dry in pods or capsules. Try to harvest seeds on a sunny day, once the dew has evaporated, then remove all pulp and fiber from their surfaces. With crops like lettuce or certain flowers that release their seeds gradually as they ripen, you may want to shake the plant every few days over a paper bag to collect the ripe seed.
Some seeds (tomatoes, for instance) are encased in a gelatinous sack that contains chemicals that inhibit seed germination, thus preventing seeds from sprouting inside the wet fruit. In nature, as the fruit rots a natural fermentation destroys this gel.
Although students in one growing classroom reported successfully planting and sprouting tomato seeds right out of the fruit, most seed savers recommend a simple fermentation process to clean tomato or eggplant seeds: Scoop out the seeds and gel, then leave them in a jar for several days in warm temperatures, stirring them occasionally. The good seed should sink to the bottom, then can be washed and dried.
Moist seeds don't keep well, so be sure to dry seeds you collect in a well-ventilated place on newspaper, paper towels, or screens for about a week. Store seeds in glass jars in a refrigerator, freezer, or other cool, dry location.
Consider creating your own packages for seeds you've grown and saved, then give them as gifts, sell them to raise funds, or trade them with a school in another part of the country or world.
Once you've tried some basic seed saving, students' questions should provide fertile ground for further research and investigations. Why do wild seeds seem harder to germinate than garden seeds? How can we cross-pollinate plants to produce different types of offspring?