While there are many native plants that attract butterflies, there is one genus of plants that is a star in this regard — Asclepias, commonly called milkweed. Historically loathed by farmers, who have long fought them in their pastures and crop rows, milkweeds offer great value to wildlife.
Three of the most common milkweeds native to Virginia are butterfly milkweed (A. tuberosa), common milkweed (A. syriaca) and swamp milkweed (A. incarnata). With pollen and nectar and to offer, all three species are magnets for bees, wasps and flies, clearwing moths, hummingbirds and an amazing array of butterfly species. Specialist bugs and beetles dine on the vegetation and some invertebrates seek shelter among these plants. Some birds use the seed “flow” of milkweeds — the milky white fluff surrounding the seed that helps it become airborne and populate other areas — to line their nests.
Milkweeds play an especially vital role in the lifecycle of the monarch butterfly, serving as the sole hosts for its caterpillars. While, according to “Milkweeds: A Conservation Practitioner’s Guide,” published by the Xerces Society, fewer than half of the 72 species of milkweed native to the United States are documented as being monarch hosts, all three of the milkweed species mentioned above are.
The common name of this plant genus comes from the milky sap or latex contained in the plants’ leaves. The cardenolide alkaloids contained in the leaves and stems makes most milkweed species toxic to vertebrate plant eaters if ingested. According the nonprofit conservation group Monarch Watch :
“When Monarch larvae ingest milkweed, they also ingest the plants’ toxins, called cardiac glycosides. They sequester these compounds in their wings and exoskeletons, making the larvae and adults toxic to many potential predators. Vertebrate predators may avoid Monarchs because they learn that the larvae and adults taste bad and/or make them vomit.”
Depending on the species of milkweed, the plants can contain anywhere from almost no toxins to so much that they are lethal even to monarch caterpillars, the website adds.
With the monarch in serious decline in the last few decades, much of that due to overuse of herbicides and other habitat destruction, planting milkweed is one of the most important conservation tools to save the butterfly. The Xerces website has a page for finding seed sources by state, and the Butterfly Society of Virginia has information on growing milkweed here in the commonwealth. Monarch Watch offers free milkweed plugs for large-scale restoration projects, such as are being executed in the Great Plains.
Among the three milkweeds mentioned here, butterfly milkweed is the most preferred by gardeners because of its bright orange flowers and short, tidy growing habit. However, it’s the least preferred by the monarch as a host plant. The much-taller common and swamp milkweeds are instead the favorites.
Despite its name, the common milkweed is anything but common in its appearance and value to wildlife. Its short flower stalks form lovely, large lavender-and-white balls that have a sweet scent. In spending some time photographing common milkweed along Skyline Drive, I found almost every bloom had at least two different species of pollinators feeding on it, from bees and wasps to butterflies and moths. Swamp milkweed, a lover of damp places, is similar to the common milkweed in its value to wildlife but has pink-and-white blossoms.
Milkweeds are easy to grow — too easy, according to its detractors; hence the “weed” part of their name. I moved a butterfly milkweed to what I thought was a better, sunnier spot for it last year, and this spring I found it had left behind two progeny, now happily blooming where their parent had been. All three plants are often visited by great spangled fritillaries, especially (I found five on one blossom this morning), but also silver-spotted skippers, eastern tiger swallowtails and others.
One place to see all three species of milkweed mentioned here is the meadow at Avon Hall, in the town of Washington. As part of a habitat restoration project there, RappFLOW and its partners have planted these and other wildflowers and grasses as a buffer for the pond on the property. Butterfly milkweed is blooming there and elsewhere now, and common and swamp milkweeds will start blooming by midsummer.
© 2015 Pam Owen
Annual butterfly count set for July 18
One way to support conservation of butterflies is to join local butterfly counts. The fifth annual Little Washington-Rappahannock count is Saturday, July 18. Founded and still hosted by Old Rag Master Naturalists, it is held in conjunction with the North American Butterfly Association’s annual summer count. The public is encouraged to participate, no experience required. Each team is led by someone experienced in butterfly identification, and ORMN is offering an optional free butterfly identification training session, with a practice field trip, on Saturday, June 27.
The count itself is held mostly on private properties, some of which require more strenuous walking than others. The chapter will match volunteers’ physical abilities to the properties. The cost to participate in the count is $5 for adults; no charge for children, who must be accompanied by an adult.
Butterflies are important as pollinators, as a food source for a host of other animals and as indicators of ecosystem health. As ORMN member Connie Chamberlin wrote in an article on the chapter’s website:
“Butterflies react very quickly to changes in their environment, which makes them excellent early warning indicators of the health of the ecosystems in which they live. If butterflies are having difficulty, the same problems that are affecting them will have an impact on other species as well. Habitat destruction, the introduction of nonnative species, pesticide use and climate change are all contributing to the decline of butterfly populations worldwide.”
Both the count and the training start at the Rappahannock Public Library (4 Library Rd, Washington, VA 22747) at 9 a.m. To register, contact Caroline Watts at firstname.lastname@example.org. For more information on this and other butterfly counts in our area, and to learn more about the importance of butterflies, visit ORMN’s website.