By Jean English
Collecting milkweed seed is a late fall tradition in our family. When the seeds are bursting out of their pods in late fall, they’re carried away on dry and windy days – or stuffed into a paper bag to sit on a shelf by our door all winter. Come spring, when the swallows return, we release the parachuted, silky white seeds into the air from an upstairs deck, sometimes being rewarded by seeing a swallow catch a fluffy seed and take it back to its birdhouse, where the fluff softens and insulates the nest for the next generation of swallows. Most seeds float to the ground, to repopulate our field with plants, which, by the way, saturate the heavy summer air with a wonderful scent when they flower.
Keeping lots of milkweed growing is important for the tough and delicate Monarch butterflies that depend on the species for their life cycle. The species seems delicate not just because all butterflies seem fragile, but also because Monarch caterpillars eat only milkweed, and milkweeds are not as common as they once were.
These insects are tough in that they, as a species, migrate from Mexico to northern North America in the spring and return to a small area of Mexico each fall. An individual adult flying from Canada to Mexico, then back to the southern United States, lives for about nine months. There it mates, lays eggs, and its offspring continue the journey, but only for about six weeks, when they stop, mate and lay eggs. The next generation continues the trip, stopping in the northern United States to mate and lay eggs, and these eggs hatch into a third generation, which summers in Canada. Somehow the Canadian-reared butterflies know how to get back to Mexico in the fall.
That “somehow” is a mystery. In an Oct. 3, 2006, article in The New York Times entitled “Fly Away Home,” writer Donald G. McNeil Jr. cites Monarch expert Orley R. Taylor, Ph.D., who says that these are one of the few creatures on earth that can orient themselves both in latitude and longitude – something humans didn’t figure out until the 1700s. Monarchs begin migrating south when the sun at their latitude is about 57 degrees above the southern horizon. This explains the “when,” but still poorly understood is how most Monarchs end up passing through an area about 50 miles wide between Eagle Pass and Del Rio, Texas. It’s got something to do with the sun. Taylor has relocated butterflies from Kansas to Washington, D.C., and noted that if he releases them immediately, they head south; but if he keeps them in mesh cages for a few days, they head for that 50-mile-wide corridor – apparently after adjusting some internal compass to coordinate with the sun. Somehow.
Will Monarchs survive long enough for this mystery to be solved? McNeil notes the threats to their survival: new flowering periods for wildflowers due to climate change; genetically-engineered corn varieties, which are grown in fields that are heavily treated with herbicides – eliminating the milkweed that once supported Monarchs; and the loss of forests in Mexico due to illegal logging.
To help the species, Taylor tracks and studies the adults, and he started Monarch Watch (monarchwatch.org) to interest gardeners and others in the subject. Monarch Watch offers seed (at shop.monarchwatch.org) for “Monarch Way Stations.” The 12 varieties of seed include milkweeds for the larvae, nectar plants for the adults, and vegetation to shelter the larvae, pupae and adults. The milkweeds are:
• Butterfly weed (Asclepias tuberosa)
• Showy milkweed (A. speciosa)
• Common milkweed (A. syriaca)
• Swamp milkweeds (A. incarnata subsp. incarnata and A. incarnata subsp. pulchra)
• Tropical milkweed (A. curassavica).
The nectar plants are:
• Prairie blazingstar (Liatris pycnostachya)
• Floss flower ‘Blue Horizon’ (Ageratum houstonianum)
• Purple coneflower (Echinacea purpurea)
• Tithonia, ‘Torch’ Mexican sunflower (Tithonia)
• Zinnia ‘Super Giant Mixed’ (Zinnia)
• Verbena (Verbena bonairiensis).
You may be growing many of these already. If not, you can order the mix and help support Monarch Watch, and the Monarchs. (You’ll also get a sign for your Monarch Way Station.)
To add to your knowledge of butterflies, you might order Storey Publishing’s 2006 book, The Life Cycles of Butterflies, by Judy Burris and Wayne Richards ($16.95). The brother-and-sister authors have shared a love of butterflies since childhood and present gorgeous photos and fascinating information about 23 common butterflies. One of my favorite books, The Life Cycle of Butterflies rarely gets put on the shelf but sits out for frequent checking and browsing. (Burris and Richards also have spectacular photos of butterflies at www.butterflynature.com.)