There are about 110 species of milkweed in North America. Among gardeners this plant is most well known to be the host plant of the Monarch and Queen butterflies. It also attracts all varieties of butterflies as a nectar plant, and its colorful flowers are a compliment to any landscape.
The name of the milkweed genus is Asclepias, the name being derived from the Greek god of medicine, Asklepios. There are many cautions about the sap of the milkweed causing eye irritation if it comes into contact with the eyes, and on the U.S. Department of Agriculture website it is advised that “milkweed may be toxic when taken internally without sufficient preparation.” However in the light of that warning the same reports also give a cultural history of how the various types of milkweed plants were used by Native Americans and pioneers: (1) Different parts of the plant were prepared and taken for medicinal purposes. (2) Fibers from the stems were used for clothing and nets. Seed silk was used for candle wicks. (3) Different parts of some varieties were actually used for food
The most common milkweed variety in present day Texas gardens is Asclepias curassavica. This variety is also known as Tropical Milkweed, Mexican Milkweed, Scarlet Milkweed, or even Blood-flower. It is native to Mexico, Central America, South America, and the Caribbean islands. It was introduced and has been naturalized in many countries in both the eastern and western hemispheres. In the mainland United States it has become naturalized mainly in Texas, Louisiana, and Florida. It is by far one o
f the easiest milkweed varieties to grow in Texas. The plant grows back quickly after being stripped by caterpillars, and with adequate water it can tolerate the summer heat. It also grows easily from both seed and cuttings. The seeds do not require cold stratification to enable germination.
A recent collaborative university study has found that because the milky sap found in Asclepias curassavica is stronger in cardenolides than many varieties, monarchs infected with the parasite ophryocystis elektroscirrha had lower parasite growth and lived longer as adults when raised (in the caterpillar form) eating this tropical milkweed variety. Another controlled study has shown that female monarchs infected with o. elektroscirrha, given a choice between swamp milkweed and A. curassavica, will lay close to 70 percent of their eggs on the more medicinal tropical or curassavica variety. This instinctive preference insures more survivability to the offspring.
There are many other beneficial insects whose life cycles involve milkweed. There is the Milkweed Tussock Moth; the caterpillars of this moth can strip the leaves from it as well. Perfectly healthy A. curassavica plants are often covered with aphids. This attracts beneficial insects such as ladybugs, lacewings, and hover flies to deposit eggs on the plant so their larvae will feed on those aphids. The larvae then go on to pupate and emerge into adulthood. So any time you are examining your milkweed, you could see some of these insects in their various stages. (The hover fly larva can be mistaken for some kind of caterpillar.) Another common insect to be found on this plant is the colorful Milkweed Bug, which feeds primarily on the seeds of the plant.
Whether it be the beauty of the flowers and the butterflies or the benefits of the ladybugs, lacewings, and hover flies, growing milkweed in your garden is a microcosm of interest.