The solution to the monarch butterfly’s disappearance GOT milkweed?

By Sara Scudier

OSU Extension master gardener volunteer

During spring and summer, monarchs breed throughout the U.S. and southern Canada. In the fall, adults of an eastern population migrate to Mexico, flying up to 3,000 miles. In the spring, monarchs return to breeding areas and the cycle starts again: a two-way migration that is one of the most spectacular on the planet.

Female monarchs lay eggs on milkweeds and a few other plants in the dogbane family. As monarchs spread across North America, several generations of butterflies are produced. Yet this migration appears to be declining. These declines in monarch butterfly populations in North America are believed to be related to a corresponding significant decline in milkweed plants. With shifting land management practices, we have lost much milkweed from the landscape.

In addition to providing a food source for monarch larvae, the showy flowers of milkweed offer abundant, high-quality nectar to many pollinators, including bees, butterflies and hummingbirds. The handsome plants can also add interest and beauty to any landscape. Milkweeds are named for their milky latex sap, which contains alkaloids and cardenolides, complex chemicals that make the plants unpalatable to most animals.

Milkweeds have a unique pollination mechanism in which the plant packages hundreds of grains of pollen into two connected sacs called a pollinarium.

The pollinator lands on a flower, the pollinarium attaches itself to the insect’s leg and, once removed from the flower, the sacs re-orient as they dry. At the next flower, the properly oriented pollinarium is deposited into a receptive stigmatic groove where the sac breaks down and the flower is pollinated.

There are many varieties of milkweed (scientific name asclepiad) to choose from. Here’s a list with their cultural requirements. Pick a variety that appeals to you and get ready to enjoy beautiful flowers and the pollinators they attract while feeding the monarch caterpillars!

Asclepias tuberosa, commonly called butterfly weed, grows well in average, dry to medium, well-drained soils in full sun. Drought tolerant. New growth tends to emerge late in the spring. This plant grows 1-2 feet tall and has showy flowers, usually yellow or orange.

Asclepias incarnate, commonly called swamp milkweed, is easily grown in medium to wet soils in full sun. Surprisingly tolerant of average well-drained soils in cultivation, even though the species is native to swamps and wet meadows. Foliage is slow to emerge in spring. Grows 4-5 feet tall with fragrant flowers.

Asclepias verticillata, commonly called whorled milkweed, does best in sunny locations but tolerates part shade. Likes hot dry soils, but tolerates moist garden soils and drought. Flowers bloom in small clusters (umbellate cymes of 3-20 flowers) in the upper leaf axils and stem ends between June and September. Flowers are fragrant. Seedpods are valued in dried flower arrangements. Grow 1-2.5 feet with showy flowers.

Asclepias syriaca, also called common milkweed, is a rough, weedy native. It is easily grown in average, dry to medium, well-drained soils in full sun. Drought tolerant. Does well in poor, dryish soils. Often forms extensive colonies in the wild. Grows 2-3 feet with fragrant flowers.

Asclepia purpurascens, commonly called purple milkweed is tolerant of dry to moist, well-drained soils. Does well in poor, dryish soils. Drought tolerant. Often forms extensive colonies in the wild. It is similar in appearance to common milkweed (A. syriaca), except its flowers are deep rose pink and its leaves are more pointed. Grows 2-3 feet with showy purple flowers.

Asclepias sullivantii, commonly called smooth milkweed, Sullivant’s milkweed or prairie milkweed, is very similar to common milkweed. Easily grown in average, medium to wet soils in full sun. Grows 2-4 feet tall with pinkish-white to pinkish-purple, starlike flowers appearing mostly in the upper leaf axils over a long bloom period from late spring well into summer. Flowers are a nectar source for many butterflies, and leaves are a food source for monarch butterfly larvae (caterpillars).

All of these plants are easily grown from seed and will self-seed in the landscape if seedpods are not removed before splitting open. Many spread by rhizomes as well. They all have deep taproots and do not like to be moved once established.

Learn to grow beautiful milkweed plants in your garden at http://go.osu.edu/milkweeds.