Monarch butterflies

If you’ve ever been on a road trip of any length, you know how hungry and weary the journey can make you. Now imagine hoofing it from central Mexico to Canada every year as a butterfly, but every time you make the trip you find fewer and fewer open restaurants and grocery stores.

This is the situation facing the iconic monarch butterfly (Danaus plexippus), the large orange, black and white butterfly known to science classrooms across the country for its bright blue chrysalis, or cocoon. Monarch butterfly larvae depend exclusively on plants in the milkweed family (Asclepias) for food, which have been increasingly targeted as a major agricultural weed across North America. The numbers of migrating adults have dropped precipitously as a result.

According to a joint study by Mexico’s National Commission of Protected Areas, or CONAP, and the U.S. nonprofit World Wildlife Fund, only about 3 acres of Mexican forest — where adults spend their winters — were found to be hosting significant colonies of hibernating adults in the winter of 2012-13, compared with nearly 45 acres in 1995-96.

The combination of earlier high summer temperatures, which kill eggs and developing larvae, and a diminished food supply have made it more and more difficult for butterflies to maintain their formerly abundant population.

Gardeners can do their part by planting milkweeds in the garden, which despite the name, are among the largest and showiest flowers to be found in the wild. They can reseed freely, hence the “weed” in its name, but deadheading flowers reduces this effect and preserves the valuable foliage for butterfly caterpillars. Milkweeds appreciate full sun and consistently moist or well-mulched spots, but are remarkably tough in hot weather. It’s hard to miss the purple-flowered types blooming in roadside ditches in the summer.

In the nursery trade, butterfly weed (Asclepias tuberosa) is the most commonly sold species, more petite in size and with distinctive lantern-shaped orange flowers and long, lance-shaped leaves. Swamp milkweed (Asclepias incarnata) and common milkweed (Asclepias syriaca) are much taller, with pink to purple flowers that persist through much of the summer, but are usually found only at native plant nurseries. A fourth species, showy milkweed (Asclepias speciosa) may need to be ordered through a specialty catalog.

Article by Michelle Donahue, FCFCDB member

Nature Note for 7/27/14