Every once in a while a truly great plant comes along. A plant that is beloved by every gardener who introduces it into their garden. ‘Iron Butterfly’ Ironweed (Vernonia lettermanii ‘Iron Butterfly’) is one of those special plants.
Years ago, when I worked at a small independent bookstore, I would be frustrated when customers came in requesting a “good book”. I felt that “good” was far too subjective, when it came to books, for me to be able to recommend something that I could be confident that every reader would enjoy. There were a very small handful of books, however, that I could point customers to with the assurance that everyone I knew who had read them had liked them. A similar situation exists with garden plants. ‘Iron Butterfly’ is the botanical equivalent of one of that handful of great books.
This dwarf thread leaf selection of Ironweed comes to us via renowned plantsman Allan Armitage of the University of Georgia. According to Richard Hawke, plant evaluation manager at the Chicago Botanic trial gardens, it is one of the most noteworthy of perennial plants that have been trialed there in recent years. Internationally acclaimed garden designer Piet Oudolf uses it extensively in his prominent public gardens. At Heyden’s Gardens, we love it, too!
‘Iron Butterfly’ sports thread-like foliage borne on upright stems that form a dense, lacy, emerald green mound. It reaches a mature height of 24”-30”, with a spread of 18”-24”. Its habit and textural foliage are appealing enough that it would be garden-worthy even if it didn’t bloom. As icing on the cake, in late summer it produces a profusion of flower buds in well-branched horizontal clusters that open to rich purple flowers in autumn. The flowers last for several weeks and provide a welcome late-season nectar source for butterflies, who visit this plant in abundance. Its purple flowers and fine-textured foliage combine particularly well with bold fall-blooming perennials such as Rudbeckia and Aster. It also pairs beautifully with ornamental grasses such as Little Bluestem (Schizachyrium) to produce a striking seasonal display.
Unlike our Wisconsin native Ironweed (Vernonia fasciculata), which thrives in moist to wet soil, ‘Iron Butterfly’ is adapted to well-drained, drier soil and is drought tolerant once established. For best form, it should be grown in full sun as it tends to become lax and less dense in shaded locations.
Although its parentage is native to southern states, ‘Iron Butterfly’ has proven itself fully winter hardy here in southeastern Wisconsin. Attractive in all seasons, reliably hardy, long-lived, well-behaved, and a Butterfly Magnet. What‘s not to like?
by Zannah Crowe
