One of the most beautiful flowers, both in flower and seed pod, as well as great importance to wildlife, has been relegated to the roadside for years and virtually ignored. Asclepias syriaca, or common milkweed, is struggling and harder to find because wild areas are disappearing and roadsides are regularly mown. “Familiarity breeds contempt” is a common saying and one that I would apply to this plant. Only when something becomes scarce do we appreciate it, and I can see that happening with milkweed. But there is a sea change coming down the pike and people are being urged to plant this “weed”.
Acknowledged as a primary source for survival of many insects, notably the Monarch, people are waking up to its integral role in supporting other wildlife. See my post Monarch Waystation on the many reasons to plant milkweed for Monarch survival.
- Milkweed is the only plant on which monarch butterflies will lay their eggs, and it is the only food source for monarch caterpillars
- It grows in colonies that expand in size every year; each individual in a colony is one side shoot of a large plant and are genetically identical or a clone; one large branching underground rhizome connects the entire colony
- Surprisingly, the flowers are extremely fragrant and you can smell a colony long before you see it
- Although one shoot may have between 300 to 500 flowers that make up the umbels, only a few of these develop into pods
- Vegetative and flower growth is rapid, but the pod development is very slow and held on the plant for many weeks
- The pods are held vertically to the plant and hold many seeds; germination of these seeds is very sparse; milkweed more likely expands by underground rhizomes than from seed
- The nectar is very high in sugar content, 3% sucrose, and the supply is constantly being renewed over the life of the flower; the flowers produce much more concentrated nectar than the many insects that feed on it could ever remove
- Milkweed teems with insect life, providing food and micro habitat to hundreds of insect varieties
- At least 10 species of insects feed exclusively on milkweeds, notably the Monarch butterfly caterpillar
- The adult Monarch lays its eggs on the leaves of common milkweed, the larvae live on its leaves and milky sap, and the adult Monarchs drink from the flower nectar, although adults will drink from other flowers
- The latex milky sap from the milkweed is extremely toxic to other wildlife and is concentrated in the tissues of the Monarch which protects it against predators
- The adult Monarch migrates south. East of the Mississippi, they fly as far as 4,800 meters to over winter in Mexico, often to the same tree location
- This relationship between the milkweed plant and the monarch butterfly makes the pairing a symbiosis, where they become one entity instead of two separate organisms. Most importantly, without the presence of the milkweed plant, monarchs would go extinct.
Other Varieties of Milkweed
Asclepias tuberosa, orange-flowered Milkweed below is probably my all time favorite for drawing insects and pollinators to the garden early in the season, around June for me in the mid-Atlantic. A long-lasting cut flower, I scatter it through my borders to brighten up early summer plantings. It comes in an all yellow version called “Hellow Yellow”.
Another milkweed which is a conversation piece oddity is Asclepias physocarpa (changed to Gymnopcarpus Physocarpus, a mouthfull!), or Hairy Balls. Forming puffy seed balls two to three inches in diameter, the orbs are covered with hairs and are quite bizarre looking. Perfect for flower arranging, the cut branches are quite expensive to buy from a florist, but easy to grow. A favored host of the Monarch butterfly, I always try to grow this plant for the odd looking pods. The caterpillars seem to prefer this variety over all others.
Tropical milkweed, Asclepias curassavica, is commonly seen growing in Florida and has bright red-orange and yellow flowers and is also a great nectar source. The leaves are narrower and the plant produces many more seed pods than the common milkweed.