Plant of the Month

September 2018

Common MilkweedMilkweed (Asclepias spp.)

  • Type: Perennial
  • Light: Full Sun
  • Water: Dry to Medium
  • Soil: Well-drained
  • Height: 2 to 3 feet; Width: 9 to 12 inches
  • Flower: Pink, Mauve, White
  • Bloom Time: May-Sept.

Most milkweeds prefer full sun although there are a few woodland species. All are considered perennial and herbaceous (not woody). Each has its own group of insect herbivores that are attracted to it for food. And although you may wonder why you would allow an insect to eat one of your plants (sometimes to the ground), rest assured that the milkweed has many defenses and coping behaviors of its own and will grow back even more hardy than before. The flowers are unique and critically important for the diversity of pollinators they support. Once established, milkweed will continue to thrive year after year in your garden and generally are easy to transplant or to propagate. Collect the seed when it is ready and then plant it right away as most milkweed seed needs to go through a winter cold to germinate. Here are some milkweeds native to the Southeast you might consider for your garden habitat:

  • Common Milkweed, Asclepias syriaca, is found widely throughout our region in sandy, clay or even rocky soils of pastures, roadsides and disturbed areas. This milkweed grows in clusters or clones spreading mostly by underground roots or rhizomes. Once established, it will spread and increase easily unless it has some sort of competition from other plants. It might be best to plant it in a field or edge of your lawn or garden where you can keep it in check. Or simply thin it out each year and share the rhizomes with other gardeners! Flowers are purplish pink to white and bloom in large balls of 100+ flowers from May through August attracting a wide variety of pollinators. Leaves are opposite, large and oval shaped. Common Milkweed can grow to over 4 feet tall in the right conditions and although it produces a lot of seeds in its characteristic seed pods, it is easier to propagate from root stock. This is by far the most popular and commonly used milkweed for monarch butterflies and it needs lots of sunshine.
  • Swamp Milkweed, Asclepias incarnata, does best in damp soil along streams and wetlands but can grow under drier conditions in gardens if soil is kept moist with good drainage. Also known as rose milkweed, this milkweed can grow 2 to 5 feet tall once established. Swamp milkweed has a tap root with some shallow and fibrous roots producing up to 6 or more stems from its crown in each growing season. It does not compete well with other vegetation. The flowers are a lovely deep rose pink in an umbel in late May through early fall, sometimes blooming twice in garden situations. This plant has long, narrow, pointed leaves that are mostly opposite. Leaves can turn purplish in full sun. This plant is not shade tolerant.
  • Butterfly MilkweedButterfly Milkweed, Asclepias tuberosa, is common along roadsides, fields and open woodlands and can be recognized by its bright, orange flowers that bloom from May through September. The leaves are mostly alternate, smaller and narrow. This plant has a deep, woody tap root up to 16 inches long and is difficult to transplant once established. It can handle sandy, loam or even rocky soils and can grow 1 to 3 feet tall spreading easily by seed. A. Tuberoses needs lots of sunlight.
  • Poke Milkweed, Asclepias exultanta, is a woodland species that can grow throughout our area on forest edges or in woodlands. It can tolerate shade and resembles the poke plant, thus its name. It has a tuberous root with one Poke Milkweedto three stems emerging from the base. Pale pinkish white flowers are loose and droop downward. Poke milkweed can grow 2 to 6 feet tall and can be easily propagated by seed.
  • White Milkweed, Asclepias variegata, thrives in open woodlands and requires some shade. Also known as red-ringed milkweed, the white flowers each have a purplish red ring forming a white ball of flowers that are striking when in bloom from May through July. Its leaves are oval shaped and opposite growing on a single stem with a fusiform rootstock. This plant can grow 1 to 4 feet tall. Although not found as commonly as other milkweeds, this would be a beautiful addition to your woodland garden.
  • Blue Sand Vine, Cynanchum laeve, is also considered a milkweed and very much resembles bindweed until its tiny, white flowers appear. Also called honeyvine, bluevine or sandvine milkweed, this plant is an important host plant for monarchs in the Southeast but be forewarned! Many gardeners consider this vine to be invasive and undesirable in a garden situation. And, a second, more important warning, there are a couple of look-alike vines that are not native and will trick monarchs to lay eggs but the tiny caterpillars will not survive. Be sure to get C. laeve if you want to support monarch caterpillars and they will help you to control this vine in your garden!

**A note about Tropical Milkweed, Asclepias curassavica. This is a beautiful milkweed that is not native to our area. It is easy to grow but there are some potential problems for monarchs associated with this plant. If you want to grow this milkweed in your garden, plan to cut it back when monarchs are migrating. You can collect seeds to scatter again in the spring. If the winter is mild, the roots will survive and send up new growth for the following year. Although this is a beautiful milkweed species, please consider planting other, native species in your milkweed garden. - by W. DeWaard

To see past Plant of the Month selections click here.

Blount County Extension Master Gardeners


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