June’s Spotlight on Butterfly Milkweed

June has ushered in a new season. Summer spells longer, brighter days, with equally bright wildflowers abloom. Butterfly Milkweed (Asclepias tuberosa, L.) burns a fiery orange among them, making it a stand-out amidst meadows, roadside foliage, or perhaps your own garden. Its large, flat-topped flower clusters also make it easy to locate for the bees and butterflies, which will alight upon the blooms wherever they are found, seeking the plant’s abundant nectar.

The genus was so-named for the Greek god of healing, Asclepius, pointing to the plant’s historical medicinal uses. Underground a brittle tuber hides (thus, ”tuberosa”) that can grow beyond 12 inches in a mature plant, storing food and water through drought. It is the raw flesh of this root which was chewed by Native Americans as a cure for pulmonary ailments from pleurisy to pneumonia, and instructions on its varied uses were later included in pharmacopoeias throughout Europe and North America. This history lends the common name, ‘Pleurisy Root’.

Another of the plant’s chemical components is used by quite a different species. As many may know, milkweeds serve as the hosts of Monarch caterpillars, happy to dine on the leaves upon which they hatch. These lovely Lepidoptera use a poison within the plant- cardiac glycosides- as protection, allowing the larvae to become not only distasteful to predators, but dangerous, too. Should a predator dare to ignore the warning colors of the Monarch, one bite will mark its memory; the poison has an emetic effect. Butterfly Milkweed, or Butterflyweed as some call it, does not contain large amounts of this poison, however, so unlike other milkweeds it will not give forth the distinct milky juice. A tear to a leaf or stem will reveal an almost clear sap.

The stem of this plant can grow to an average 2 feet tall, whilst covered in small hairs and sporting lance-like leaves in alternating fashion. Its 3-inch leaves are shiny green on the top and lighter underneath, each covered in a downy fur of fine hairs. A young plant may contain only one central stem, while aging brings about a bushy, branching forb with upwards of 12 stems all protruding from the impressive taproot below. Cuttings of the root make for successful propagation, and it is suggested that 2-inch sections be planted vertically and kept moist. Once established, the plant perfers dry, sandy soils with a PH of 4.8-6.8.

In autumn the showy flowers of summertime will be replaced by dangling seedpods that will brown and burst to reveal the seeds within. The seeds are fixed with silken threads (a pappus parachute!), meant to catch the wind and disperse the plant to new destinations. With a ‘host’ of uses for butterflies and bees alike, Butterfly Milkweed’s current destination is this month’s Spotlight.

• Additional information on this species can be found at this native plant database.
• A map of the native range of Butterfly Milkweed is available here – USDA PLANTS
• For in-depth folk medicinal uses of Asclepias tuberosa, visit Earth Notes.
• Asclepias appears on Dr. Douglas Tallamy’s 20 Most Valuable Plant Genera in terms of supporting biodiversity in the mid-Atlantic region, reportedly supporting 12 species of moths and butterflies -full pdf 

This article showcases the photography of NPSNJ’s own Belinda Beetham. For more naturalist photos, visit her flickr.