Focus on Natives: Ironweed

One of the very first native plants to volunteer in my garden was ironweed. It grew to 8 ft tall which puts the flowers right at eye level when we sit on the front porch. The beautiful purple flowers attract so much attention from pollinators, swallowtail butterflies and monarchs that I knew it would be a great addition to the ecosystem I wanted to create in my yard.

Ironweed, a member of the Asteraceae family, (Vernonia spp) has many species which will readily hybridize so it can be difficult to positively identify the exact species. Adding to the difficulty in identification the common names are frequently interchanged. Within each species there may be variations of flower color, leaf shape and number of florets. In Ohio, the most common variety is Giant Ironweed (Vernonia gigantea) but you may also find New York Ironweed or Smooth Ironweed. These are perennial plants which rarely need to be divided, are easy to grow and are deer resistant. Although they can be 5 to 8 feet tall they don’t require staking because the stems are sturdy. My plants made it thru the recent hurricane without falling over. If you prefer a shorter plant you can cut them back in June to about 2 feet or cut them back to different heights for a more layered effect of the flowers.

Ironweed does best in full sun but can be grown in partial sun (2 to 6 hours). Soil can be clay, loam or soil with high organic matter. Its preference for moist soil makes it a good choice for those wetter areas in your garden, along streams or in a rain garden. Bloom time is from July to September. The flowers are deep purple, disc flowers which are at the same level as other flowers within the cluster. The leaves are large, up to 9” long and 2” wide with serrated edges and are arranged on the stems alternately.

In addition to the ease of growing and caring for Ironweed it is a valuable plant for a native long-horned bee called Melissodes denticulatus. This bee flies from July through September in synchrony with the ironweed bloom. This native solitary bee is black with gray hairs and blue eyes. The pollen they collect from the ironweed is WHITE!

Other pollinators it attracts are flies, skippers, monarchs, swallowtails and the Great Spangled Fritillaries. Caterpillars of many moth species feed on ironweed. Songbirds will feast on the seeds in late fall.

Ironweed will be at home in many types of landscapes like butterfly gardens, cottage gardens, native gardens, pollinator gardens and rain gardens. It will reseed prolifically so you would probably want to deadhead in the fall after the blooms fade into brown.

With all of these attributes it is hard to imagine you wouldn’t want to have some ironweed in your garden. I personally love thetall, native variety that came unexpectantly but there are some cultivars now like “Summer Surrender” and “Summer Swan Song” that have a bushy habit and even one with white flowers named “White Lightning”.

Submitted by: Valerie Shaw

September 10, 2024

Sources:

North Carolina Extension Gardener Plant Toolbox

Buckeye Yard and Garden Line: “You can Never Have Too Much IRONWEED! Part 1” and “An Ironweed Specialist Bee”