Milkweeds

Milkweeds

By

Frank W. Porter

Porterbrook Native Plants

One of the most breathtaking summer-blooming wildflowers is Butterfly Weed (Asclepias tuberosa). Its umbels of orange, yellow, and occasionally red blossoms attract not only hundreds of butterflies but many other insect pollinators. The common name, Milkweed, in all probability stems from the fact that when cut or bruised all parts of the plant exude a white and sticky sap. This milky sap contains poisonous glycosides similar to those found in Foxglove plants. The genus, Asclepias, comes from the name of the Greek god of medicine, Aesculapius. Native Americans and early colonists used several Asclepias species for medicinal purposes. Removal of warts was one use. Monarch butterfly caterpillars ingest this milky sap, but are not harmed. Instead, their bodies become bitter tasting and even poisonous to predators. Even after their transformation into beautiful butterflies, this protection continues.

Butterfly Weed is only one of more than twenty species of Asclepias growing east of the Mississippi River. The leaves of Asclepias species are usually opposite, although sometimes they are whorled and on rare occasions alternate. The leaves vary in shape from thick ovals to very thin needles. The stems frequently are simple and solitary. It is the variations in their flower structure that help to distinguish these species. Every small blossom has a downward-pointing corolla, which consists of five petals and five hidden sepals. The upward-pointing part is a five-lobed crown of hoods with horns around a central column of stamens and pistils. They are connected together by a pedestal. Several blossoms are grouped together to form an umbel.

These showy flowers produce nectar that is attractive to bees and butterflies. The unusual structure of the flowers, however, allows pollination in two complex ways. In early summer, buds begin to develop. Pollen sacs develop on the stamens. Visiting insects must accidentally slide one of their legs through a slit and into the interior of the flower. These pollen sacs snag on the insect’s leg and get pulled off the stamens. The insect must successfully remove the leg and the attached pollen sac from the slit. If the insect is not successful, the leg may be left behind or the insect may die because of being permanently stuck to the flower. I have found the legs of insects on several flowers. If successful, the insect must reach another flower and have the leg containing the pollen sac slide through the slit of the second flower. The pollen must be inserted into slits behind the crown exactly or the pollen grains germinate the wrong way and are wasted. Once all of these conditions are satisfied, the Milkweed flower has successfully been pollinated. This is one reason why so few pods develop on most plants.

Milkweed, in addition to being a significant source of nectar for numerous butterfly species, is the host plant for Monarch butterflies. Without milkweed, Monarchs would be unable to survive. And we would no longer have their bright orange and black wings to grace our gardens.

Milkweed has also been useful to humans. The roots of Asclepias tuberosa were once used to make a tea or tincture for inflammations of the lung (pleurisy)—hence the common name Pleurisy Root. A poultice made from the roots helped to heal bruises, swellings, and rheumatism. Asclepias incarnata was also used to make a root tea as a laxative. Early settlers used it for asthma, syphilis, worms, rheumatism and as a heart tonic. Asclepias quadrifolia was used by the Cherokee to make a root tea for kidney stones. The leaves were also rubbed on warts to remove them. Asclepias syriaca had similar uses. The silky seed tassels served as stuffing for pillows and feather beds. And in World War I it was used to stuff life jackets of sailors and pilots. A word of caution, however, is necessary. All parts of milkweeds are potentially toxic. And the silky seeds are extremely flammable.

The habitats of milkweeds range from sandhills to swamps and from full sun to shade. The most widespread milkweed is Asclepias tuberosa. It grows along roadsides and meadows throughout the summer. Butterflyweed is unlike other species of Asclepias because it does not have a milky sap and the leaves are alternate. Asclepias syriaca , Common Milkweed, did not originate in the Middle East as its name suggests. Instead, Linnaeus mistakenly placed it in a pile of plants from that region and gave it the species name of syriaca. It attracts hordes of pollinators; and it is the primary food source of monarch butterfly larvae. It is a tall, downy plant with broad oval leaves which bear slightly drooping umbels of pinkish purple blossoms. It should not be grown in the garden because it has underground stolons which will quickly spread. This characteristic, however, makes it an excellent candidate for restoration of natural areas. Asclepias speciosa, Showy Milkweed, is similar to Common Milkweed but the flowers have larger and more tapering upright petals and an abundance of wooly hairs.

Some species of Asclepias prefer marshes, swamps, stream banks, or moist meadows. Asclepias exaltata, Poke Milkweed, inhabits moist woods and wooded edges. The white or pinkish flowers are arranged in spreading and frequently drooping clusters. Aslcepias incarnata, Swamp Milkweed, grows in marshes and shores of wetlands. Clusters of pink to rose-purple (and occasionally white) flowers will brighten any moist garden area. Asclepias lanceolata, Fewflower Milkweed, has a red corolla and orange crown and has narrow lanceolate leaves. It favors savannahs, swamps, and marshes. Asclepias longifolia, Longleaf Milkweed, possesses a greenish white corolla with rose tips. Its narrow linear leaves grow in irregular pairs. It is a denizen of savannahs, low pinelands, bogs, and and swamps. Asclepias rubra, Red Milkweed, has a dull red-lavendar corolla and opposite ovate-lanceolate leaves. It grows in bogs, swamps, and wet meadows. Asclepias perennis, Aquatic Milkweed, has a white corolla and elliptic-lanceolate leaves with long pedicels and petioles. It inhabits swamp forests.

Other species of Asclepias grow in open woods. Asclepias variegata, Redwing Milkweed, haunts the shade of woodlands. Its umbels of white flowers have a red-purple ring around the pedestal. These bright white flowers are like beacons in the woods. Asclepias amplexicaulis, Clasping Milkweed, has a rosy-pink crown and yellow-green corolla. Its large oblong leaves possess wavy margins and grown on reddish stems. Asclepias quadrifolia, Fourleaf Milkweed, has a greenish white to pink corolla. The flowers grow on long pedicels, and the four leaves are in whorls around the stem. Asclepias verticallata, Whorled Milkweed, has small flowers with a greenish white corolla. The narrow and threadlike leaves are in whorls around the stem. Asclepias purpurascens, Purple Milkweed, has a deep rose corolla and opposite ovate to elliptic leaves. It is becoming increasingly rare due to loss of habitat.

Several species of Asclepias are quite rare and in dire need of conservation and protection. Asclepias cinerea, Carolina Milkweed, is a small plant with a lavender corolla and narrow linear leaves. It grows in pine/palmetto flatwoods and savannahs. Asclepias connivens, Largeflower Milkweed, is quite rare and can be found in wet savannahs. Asclepias obovata, Pineland Milkweed, has a yellow-green corolla with opposite elliptic to ovate leaves. It prefers sandy pinelands. Asclelpias pedicellata, Savannah Milkweed, has a greenish cream corolla and narrow linear leaves. It inhabits savannahs along the coastal plain. Asclepias tomentosa, Tuba Milkweed, has a yellow-green corolla with an orange tint and tuba-like hoods. The leaves are oblong. It grows in sandhills and pine woods.

The flowers of some Milkweeds are greenish. Asclepias viridiflora, Green Comet Milkweed, has a pale green corolla and oblong leaves with a wavy margin. Although not abundant, it can be found in fields and along roadsides. Asclepias viridis, Green Antelopehorns, has a yellow-green corolla with reddish to pink-purple hoods and oval pointed leaves. It prefers fields and pine woods.

No matter what part of the eastern United States you live in, there are species of Asclepias that should be an integral part of your garden or landscape. Milkweeds not only provide a wide array of flowers but also serve a functional role as host plants for certain species of butterflies and other insects. And we must begin to take notice of the rare and increasingly endangered species of Milkweeds and initiate efforts to protect and conserve them so that future generations will have the opportunity to enjoy these beautiful wildflowers.

Reprinted with permission of the Marietta Register