"My tenth graders had paired up with elementary students to fill a butterfly nectar garden with butterfly bush, black-eyed Susans, and so on, then realized the need for larval host plants," reports Collegeville, PA, teacher Sandy Sweeney.
Students knew from researching the monarch that the caterpillars needed milkweed, so they decided to collect its seeds and try to raise seedlings in the GrowLab to transplant to the garden.
The students hypothesized that milkweed seeds would require an overwintering period, then brainstormed factors, such as temperature and moisture, that might affect subsequent germination. Small student groups prepared seeds under different conditions: placing some in damp towels in plastic in the fridge; freezing some; and leaving others in a warm, dry location, for instance.
"We discovered that the milkweed seeds that had overwintered in damp, cool conditions were most likely to germinate," explains Sandy. After raising the survivors under lights indoors, students transplanted the seedlings to the garden. "We learned that we should have watered the transplants more thoroughly," says Sandy."Only 25 percent survived, but those that did are beginning to host new generations of caterpillars," she adds.
Milkweed is considered a noxious weed by some people, but students had a chance to see and appreciate its importance in the web of life, says Sandy. "We're in an area that's undergoing a suburban boom, and many of the wild plants are being destroyed to make room for development. The project inspired the kids to write eloquent letters to editors and officials outlining why it's important to maintain some open spaces," she adds.
If your students want to try growing milkweed from seed to provide food for monarch caterpillars, consider ordering seeds from Monarch Watch or collecting them in the fall when the pods are ready to burst. Most Northern species will need to be cold-stratified -- planted in moist sterile potting soil, and kept for three months in a refrigerator -- before they'll germinate. Plant the seeds just beneath the soil surface in a deep pot, since milkweed has a taproot, and keep them warm (70° to 75° F). Fertilize seedlings once a week and keep the tops pinched back to encourage full, leafy growth.
If you're raising butterflies indoors, simply put the entire plant into your caterpillar-rearing chamber. If you're transplanting seedlings outdoors, put them 1 to 2 feet apart when they're about 3 inches tall, and provide plenty of moisture.
Once larvae polish off the leaves, cut the plants an inch above the soil, and they should regrow. (Also consider challenging your young scientists to investigate whether they can grow milkweed from cuttings.)