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Species Spotlight: Butterfly Milkweed (Asclepias tuberosa)

Butterfly Milkweed in flower

Interesting Facts:

  • Genus name honors the Greek god Asklepios the god of medicine.

  • Butterfly weed does not contain the characteristic thick milky sap but instead has a watery translucent sap.

  • Because of the absence of milky latex, it is often referred to as Butterfly Weed, rather than Butterfly Milkweed

  • Native Americans harvested fibers from the dried stems that were made into ropes and used in weaving cloth. 5 stems generally yields about one foot of cordage.

  • Pleurisy root was listed in the American Pharmacopoeia and the National Formulary until 1936

Native Environment/Plant Information:

Butterfly Milkweed is a compact, clump-forming member of the Dogbane Family. It generally grows 1 to 2.5 feet tall and can take 2-3 years before it flowers. Butterfly Milkweed have tuberous roots and consisting of a woody taproot that is thick and knobby and can extend several feet below the ground surface. This is part of the reason Butterfly Milkweed has a clumping habit and can form small, dense colonies. Basal leaves can get dense after a few years. When ready to flower, Butterfly Milkweed will send up a stiff stalk with alternate leaves that get smaller further up the stem. Stems are generally upright with hairy, unbranched stems. Young plants generally develop a single central stem, while older plants tiller at the base, sending up multiple erect stems. The alternate leaves are generally 2-3 inches long and ½–¾" across. The flowers form at the end of the stem in clusters (umbels) of bright orange to yellow-orange flowers. The umbels span 1–2½" across and consist of 8-25 flowers each. While individual umbels are slightly dome-shaped, the umbels of different stems on the same plant are often horizontally adjacent to each other. Umbels of flowers often develop in the axils of upper leaves develop. The flowers consist of 5 sepals, 5 petals, 5 hoods with horns, and a central reproductive column that is white to light green and short. The petals, hoods, and horns are generally orange but sometimes are reddish orange or yellowish orange. The flowers are long-lasting and colorful. Flowers give way to prominent, light-green, spindle-shaped seed pods (3-6" long) which split open when ripe and release numerous silky-tailed seeds that are wind-dispersed.

Butterfly Milkweed is a very common plant in prairies and grasslands and prefers dry open habitats and full sun. It is tolerant of drought conditions and can grow in a wide range of soil textures. Butterfly Milkweed is most commonly found in open, upland sites such as upland fields, sand prairies, hill prairies, sandy savannas, open rocky woodlands, abandoned fields, roadside embankments, and along railroads and roadsides.

Cultural Information:

Butterfly Milkweed is easiest to grow in sunny locations. Butterfly Milkweed prefer well-drained dry to average soil and is drought-tolerant and does well in poor soils where competition from other plants is reduced. It does best in acidic soil that is sandy or rocky. However, Butterfly Milkweed will adapt to other kinds of soil, including those that contain loam or clay, if they are well-drained. The plant develops somewhat slowly but is easy to cultivate in open, sunny areas once it becomes established.

Butterfly Milkweeds new growth does not generally emerge until May. It is susceptible to crown rot in wet, poorly-drained soils and does not transplant well due to its deep taproot. Once established it is best left undisturbed. Deadheading can prolong more blooms throughout the season, though it often blooms twice (July and September) in this area without deadheading. Milkweeds and Dogbanes can be burned in the fall to eliminate dead stalks and stimulate new growth. Burning causes new growth to have taller, straighter stems (with longer fibers). It also stimulates flower and seed production.

Since Butterfly Milkweed is long-blooming and clump-forming, they work well in many situations. It pairs well other blue and purple flowers, native ornamental grasses and wildflowers, such as asters, to a create a butterfly habitat. Butterfly Milkweed works well in Butterfly Gardens, Pollinator Gardens, Rock Gardens, Drought-tolerant Gardens, along patios and walkways, Perennial Borders, Meadows, Prairies, or Naturalized/Native Plant Areas. It is also an effective plant for sunny borders or slopes.

Butterfly Milkweed has had many uses. It is also commonly called Pleurisy Root due to the root’s prior medicinal use of to treat pleurisy (lung inflamation)<1>. A tea of root was made to treat pleurisy, asthma, bronchitis and also served as a laxative, diuretic, and expectorant<7>. Omahas and Poncas ate the raw root of the butterfly milkweed for bronchial and pulmonary troubles<5>. Pleurisy root is a stimulant to the vagus nerve, producing perspiration, expectoration, and bronchial dilation<5>. Fibers from milkweed stems have been identified in prehistoric textiles in the Pueblo region. Tewa-speaking people of the Rio Grande still make string and rope from these fibers<5>. Young shoots, stems, flower buds, immature fruits, and roots of butterfly milkweed were boiled and eaten as a vegetable by various indigenous groups of eastern and mid-western America<5>. However, all parts of the plant are mildly toxic due to cardiac glycosides and resinoids<2>. Symptoms can include vomiting, stupor, weakness, spasms<2>. Seed pods can be used in dried flower arrangements.

All parts of the plant are said to stimulate the immune system but should not be used by immuno-compromised people<7>. Butterfly Milkweed was one of the most important plants used by Native Americans<5> and was used as a pain reliever, anti-inflammatory, a treatment for toothaches, coughs, colds, and sore throats. Overall, studies have proven inconclusive on the effectiveness for various supposed treatments <6>. Some studies have shown that Butterfly Milkweed is an immune system booster<5> and that compounds extracted from Echinacea species have shown inhibitory effects against certain forms of cancer <5><6>.

Butterfly Milkweed

Wildlife uses:

The flowers are a nectar source for many butterflies and insect pollinators. The flower nectar attracts honeybees, digger bees (Melissodes spp.), leaf-cutting bees (Megachile spp.), Halictid bees (including green metallic bees), thread-waisted wasps (Ammophila spp.) and other Sphecid wasps, and butterflies, including Fritillaries (Speyeria spp.), Swallowtails (Papilio spp.), and the Monarch (Danaus plexippus); see Robertson (1929). Some insects feed destructively on the leaves, flowers and buds, seedpods, and other parts of Butterfly Milkweed. These insects include larvae of the Blackened Milkweed Beetle (Tetraopes melanurus), the Small Milkweed Bug (Lygaeus kalmii), the Large Milkweed Bug (Oncopeltus fasciatus). Butterfly Milkweed is a larval host plant for monarch, which can have one to three broods in the north and four to six broods in the south, the gray hairstreak, and milkweed tussock moth caterpillars. The Curve-tailed Bush Katydid (Scudderia curvicauda), has been observed feeding on the leaves of this milkweed.

The Ruby-throated Hummingbird is also attracted to the flowers.

Milkweed species are known to contain cardiac glycosides that are poisonous both to humans and livestock. They also contain other substances that may account for their medicinal effect. Resinoids, glycosides, and small amounts of alkaloids are present in all parts of the plant<5>.

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