That old standby definition of a weed—any plant growing where it’s not wanted—doesn’t always apply in the world of herbs. Their usefulness and sometimes neglected beauty make them welcome guests despite their eagerness to run unchecked through the garden.
Never has there been a more attractive and useful group of weeds than the milkweeds, more than 100 species belonging to the genus Asclepias and distributed mainly throughout North America and parts of southern Africa. Most are straight-stemmed herbaceous perennials, but a few are shrubs that may grow 12 feet tall. The leaves vary from impressively large, broad, and woolly to threadlike and smooth. They may be arranged on the stem in opposite pairs, alternately, or in tight whorls. A few desert species are virtually leafless. The New Mexico herbalist Michael Moore has described them as “truly weird . . . smooth sticks stuck unceremoniously in the sand”, a simple utilitarian design for a harsh environment.
The numerous, showy, and often scented flowers are usually borne in clusters called cymes, either at the ends of the stems or in the leaf axils. They are ingeniously adapted to pollination by insects. At the top of every flower is a crown of five pouches, or hoods, each containing an enticing stash of nectar. As an insect alights on a flower, its legs are guided down into grooves, where one of its hairs or claws catches on a structure connecting two waxy masses of pollen called pollinia. The insect flies off to another flower, then browses among its hoods for nectar and dislodges the pollinia, which then pollinate the second flower.
Flowers that get pollinated produce large, spindle-shaped seedpods. Some species have silky smooth pods; others, warty or spiny ones. Inside each pod are numerous seeds, each with a tuft of long, silky hairs. When the pods split open, the hairs act as little parachutes. Anyone who has played with milkweed pods as a child remembers the silky down and the gently rising seeds. In the words of the botanist Charles Millspaugh in his book Me-dicinal Plants (1892):
Balanced by the pendant seeds, they mount gracefully to immense heights, whence they are wafted far and wide by the lightest zephyr until, dampened by dew or rain, they fall.
The name “milkweed” comes from the milky latex that exudes when a milkweed plant is wounded. Contact with the latex irritates the skin of some people, but it benefits the plant by deterring munching by herbivorous animals. Attempts to produce synthetic crude oil from this latex have proven unsuccessful.
Milkweeds As Medicine
The generic name Asclepias honors Asklepios, the Greek god of medicine, so highly did Native Americans and European settlers value milkweeds as medicine. Millspaugh (who apparently was enamored of the genus) summed up the manifold uses of one species, A. tuberosa, known to gardeners as butterfly weed but to herbalists as pleurisy root:
The pleurisy root has received more attention as a medicine than any other species of this genus, having been regarded almost since the discovery of this country as subtonic, diaphoretic, alterative, expectorant, diuretic, laxative, escharotic, carminative, anti-spasmodic, anti-pleuritic, stomachic, astringent, anti-rheumatic, anti-syphilitic, and what not.
I don’t know what half these terms mean, but I, too, am impressed. This species was listed in the U.S. Pharmacopoeia as late as 1936.
Several species are still used medicinally by herbalists. The latex from showy milkweed (A. speciosa) and common milkweed (A. syriaca) is used as a treatment for warts, ringworm, and other skin ailments. Root extracts of pleurisy root are used for respiratory disorders and those of common and swamp milkweed (A. incarnata), for intestinal parasites. Paralleling this latter use, the U.S. Department of Agriculture is currently investigating the nematode-fighting properties of ground milkweed seeds. Someday, gardeners and farmers may be able to add them to their arsenal of natural nematocides.
Milkweeds As Food
Several milkweeds have been traditional Native American foods. When properly prepared by repeated blanching to remove the bitterness, tender young shoots, leaves, flower buds, and seedpods of common and showy milkweeds are edible, even tasty. To be on the safe side, avoid the other species, which may be or are known to be more toxic. Choose shoots no longer than 6 inches, leaves that have just opened, flower buds that look like loose heads of broccoli, and seedpods that are no more than 2 inches long. Place the parts to be eaten in a large pot and cover with boiling water; boil for one to two minutes and drain. Repeat these steps three more times (failure to use boiling water can set the bitterness instead of removing it). Then cook the vegetables until they are tender and serve with lemon and butter, or stir-fry with olive oil and other vegetables. The pods may need 30 minutes of cooking to become tender. If after cooking they are still too tough, split them open and just eat the insides, which have a nutty flavor.
Early French Canadians also made a kind of brown sugary sweetener from the flowers. According to Thomas Jeffreys in his Natural History of Canada (1760):
[T]he cotton-tree [A. syriaca] . . . is crowned with several tufts of flowers; these are shaken early in the morning before the dew is off of them when there falls from them with the dew a kind of honey, which is reduced into sugar by boiling.
Delightful as it sounds, it probably isn’t a replacement for maple syrup.
Milkweeds As Fiber
If eating the pods doesn’t appeal to you, consider some other possible uses. Native Americans used the silk, or floss, to line their children’s cradles, and Europeans wove it into fabric as early as the seventeenth century. Traveling in Canada, the Swedish naturalist Peter Kalm observed in his diary (1749):
The pods of this plant (A. syriaca), when ripe, contain a kind of wool, which encloses the seed, and resembles cotton, from whence the plant has got its French name (le Cotonier). The poor collect it and fill their beds, especially their childrens, with it instead of feathers.
Though tedious to collect (it takes several hundred pods to yield a pound of floss), the poor made a wise choice: tests have shown that milkweed floss has the same density as goose down and is an even better insulator.
During World War II, schoolchildren were encouraged to collect bags of floss to be used as stuffing for life jackets in place of kapok, which was not available. A Nebraska company currently processes more than 3,500 pounds of floss each year to blend with down as a filling for comforters, jackets, and pillows. There is renewed interest in Europe for creating textiles containing milkweed floss. The silks are too short to be easily spun into thread alone, but they add sheen and strength when blended with cotton and flax.
Native Americans also used the fibrous stems to make nets, cordage, and basketry; common milkweed has been identified in artifacts believed to be nearly 3,000 years old. The USDA studied the commercial production of milkweed fiber in the early part of this century, but few farmers gave it a try.
Milkweeds In The Landscape
Useful as these “weeds” are, let’s not forget their beauty in the garden. Many are handsome, even stately plants and are suited for varied positions in the landscape. Some, such as butterfly weed and swamp milkweed, look best in massed plantings or large clumps. Others, such as the common milkweed, look uncommonly good as single specimens in the perennial border. All are great additions to natural plantings and wildflower meadows.
One of the other charms of milkweeds is their associations with insects. Find a comfortable spot on the grass near a clump of milkweed in bloom and witness its attraction for nectaring bees and butterflies, especially the monarchs, which lay their eggs only on Asclepias species. After the eggs hatch, you can watch the exquisitely striped caterpillars as they feed on the leaves, developing the bad taste that protects them from predators. You may even be lucky enough to see an adult monarch as it emerges from its jewellike chrysalis.
A patch of milkweed is a source of fascination and learning for children that ends only with the frosts of fall and the playful dispersal of the silk-laden seeds. Young children should probably be supervised when near the plants because of the possibility of contact dermatitis. The plants are so bitter that it’s doubtful that a child would ingest a toxic quantity.
Most milkweeds die back each winter to underground buds and rhizomes. Many emerge very late in the spring. An easy way to mark each plant so that you don’t disturb it with early spring cultivation is to leave last year’s dead stalks in place until the new growth appears. The tall stems and their pods add interest to the winter garden.
Milkweeds are easily propagated from seeds. Seeds that are only a few months old usually germinate within four to six weeks at 65° to 75°F. The germination of older seeds may be hastened by mixing them with moist perlite or sand and refrigerating them for six weeks before planting. A few of the shrubby species can also be propagated from stem cuttings.
Although milkweeds are fairly pest-free, aphids can become a nuisance. Insecticidal soaps, which do not harm the beneficial insects that visit the flowers, will control the aphids but are also toxic to caterpillars. We have sometimes removed monarch caterpillars, sprayed the plants, washed off the dead aphids, and then replaced the hungry monarchs. Better to learn to live with a few aphids until the caterpillars have become butterflies and flown away.
Most milkweeds are found in dry or well-drained soils in nature and do best under these conditions in the garden. Common and swamp milkweed can tolerate dryness but look their best in moist soil. All milkweeds need full sun. Fertilize them as you would your other flowering perennials. Many species are very cold hardy, and those that aren’t can easily be grown as potted plants.
Blood flower (A. curassavica)
This is a tender species found in Central America and parts of Florida, Louisiana, and Texas. The flowers are bright reddish orange with contrasting yellow hoods, the most brilliantly colored of any of the milkweeds I’ve grown. Plants are evergreen if given enough light and warmth in winter and can become small shrubs 2 to 3 feet tall. Hardy only to USDA Zone 9, they can be treated as annuals or grown in large pots and brought indoors for the winter. Propagation is by seeds. ‘Silky Gold’ is a cultivar with solid yellow flowers.
Swamp milkweed (A. incarnata)
This is a well-branched, herbaceous plant growing 2 to 3 feet tall. The flowers are deep rose or pink with whitish hoods and bloom for several weeks in midsummer. The leaves are 3 to 6 inches long, smooth, and deep green. Though often found growing in wet areas, it does well in good, evenly moist soil and is one of the easiest and most reliable milkweeds to grow in the garden. The 3- to 4-inch-long pods dry well for floral designs after they have split open and released their seeds. Propagation is by seeds. ‘Ice Ballet’ has pure white flowers. Zones 3 to 8.
Showy milkweed (A. speciosa)
If you spot a milkweed along western roadsides and railways, it’s probably this species. An erect plant, it has large, velvety leaves and pinkish purple fragrant flowers. The pods are quite large and warty. This is an excellent choice for a xeric garden, as its natural habitat is one of winter rain and hot, dry summers. It might appear too coarse for some gardens, but its woolly-stemmed stoutness is right at home among rocks and natural plantings. Propagation is by seeds. Zones 3 to 9.
Common milkweed (A. syriaca)
This is the milkweed most often seen in the eastern United States. It can reach magnificent proportions, with leaves 10 inches long on plants 5 to 6 feet high. The pinkish purple flowers are followed by large, drooping, softly spiny pods. Plants are easily grown in the garden but can be invasive. A barrier of metal edging sunk into the ground around the clump may slow the wandering rhizomes. Propagation is by division or seeds. Zones 4 to 9.
Butterfly weed, pleurisy root (A. tuberosa)
This is the showiest herb in our garden, made even more dazzling by the butterflies that frequent its blossoms. The species bears yellow to bright orange flowers that bloom from midsummer on, but some plants grown from the seed mixture ‘Gay Butterflies’ may produce flowers that are nearly red. I’ve found that butterfly weed is not long lived, especially in habitually wet soils, but its spectacular appearance when in bloom makes occasional replacement well worth the trouble. The 4- to 5-inch-long smooth tan pods are our favorite milkweed for dried decorations. Propagation is by seeds. Zones 4 to 9.
The following less commonly cultivated milkweeds are also worth looking for. Purple milkweed (A. cordifolia) is similar to A. speciosa in its appearance and garden requirements, but the leaves are heart-shaped and the flowers deep purple. Whorled milkweed (A. verticillata) has threadlike leaves arranged in whorls and white flowers. A. rotundifolia, a tender African species that’s a small shrub in its native habitat, has attractive leathery, round leaves and makes a handsome potted specimen.
• The following companies offer selections of seeds and/or plants of Asclepias species.
• Busse Gardens, 5873 Oliver Ave. S.W., Cokato, MN 55321-4229. (800) 544-3192. E-mail firstname.lastname@example.org. Catalog $2.
• Carroll Gardens, 444 E. Main St., Westminster, MD 21157. (800) 638-6334. Catalog $3.
• Forestfarm, 990 Tetherow Rd., Williams, OR 97544-9599. (541) 846-7269. Catalog $4.
• Goodwin Creek Gardens, PO Box 83, Williams, OR 97544. (541) 846-7357. Catalog $1.
• WE–DU Nurseries, Rt. 5, Box 724, Marion, NC 28752. (704) 738-8300. E-mail email@example.com. Catalog $2.
Jim Becker and his wife, Dotti, raise milkweeds and hundreds of other herbs at their nursery, Goodwin Creek Gardens, in Williams, Oregon.