Plant of the Week: Ironweed (Vernonia gigantea)

Most agriculture folks consider tall ironweed as just that, "a weed."  I guess because it can take over pastures and cows won't eat it.  However, from a native plant standpoint, this 3 - 7' tall weed puts on a spectacular show and is a great butterfly attracting plant especially for migrating monarchs.  This is a highly variable species and will readily hybridize with V. missurica (only in the far western regions along the Mississippi River in Kentucky).  We also have another rare species in the state, New York Ironweed (V. noveboracensis).  Ironweed loves moist soils but will tolerate pretty much most soil types found in urban environments.  Flower color varies from deep purple to light purple and even purplish-red.  The leaves can be up to 10" long and 2" wide and are arrowhead shaped, in general, with serrated edges. The leaves are either sessile or have a short petiole where they attach to the stem which is usually slightly hairy.  The flower clusters have been 10 and 30 disk florets but no ray florets.  Each floret has 5 tubular recurved lobes (just the right length for its pollinators of bee flies, butterflies, long-tongued bees, and skippers.  Mammals leave this plant alone because it has bitter tasting foliage.  The root system is fibrous and rhizomatous and each rhizome can produce several plants.  My recommendation for keeping this tall growing plant at a reasonable size is to cut it back in mid-June.  This plant works well with goldenrods and yellow wingstem (both of which would probably need to be cut back as well) and if you want a butterfly paradise, place it in combination with joe-pye-weed, goldenrods, and boneset.  This plant is an excellent self-seeder and in the garden the flower heads should be dead-headed to prevent unwanted plants from popping up everywhere.