Sunday, July 25, 2010
Giant Ironweed - Vernonia gigantea
As its common name implies, giant ironweed (Vernonia gigantea) is the tallest and most robust member of this genus. It is found throughout the northern two-thirds of the state and in much of the eastern half of the nation - to southern Canada. It is an adaptable plant and occurs in a wide variety of habitats. Often, it is found in light gaps and the edges of wooded habitats, but it is equally abundant in sunnier locations as long as soil moisture is adequate.
Giant ironweed is deciduous and dies back to the ground each winter. The cluster of tough basal leaves emerges in the early spring. These are oval shaped, rather coarse and decidedly toothed along the margins. By late spring, the central stalk begins to elongate and by late June to early July, the broad and rounded clusters of flowerheads are fully formed. Each plant may stand 4-5 feet tall, depending on growing conditions.
Flowering occurs in July and can extend into August. Deep rich-lavender aster flowers form small clusters across the crown of each plant. These last for weeks and attract a wide assortment of butterflies and other pollinators - making this an excellent choice for a butterfly garden.
Giant ironweed can sucker extensively in the garden and will eventually move around to the places that best suit its growing requirements. For this reason, some weeding is often necessary to confine it to the parts of the garden it is welcome. Because of its size and height, it is best used in the back of the mixed wildflower garden. Plant it in small clusters of 3 or 5, spaced about 18 inches part and the plants will spread and form a solid cluster in relatively short time. These can be breathtaking in the right setting.
I have "lost" this species during periods of extended drought if I haven't watered sufficiently. Although it is tolerant of a variety of conditions, it will not prosper in settings that remain too droughty. If you have a moist location, use it in full sun and the butterflies will be attracted even more.
Giant ironweed is thankfully grown by a number of commercial sources, including members of AFFN - the Association of Florida Native Nurseries. We have kept it in our landscape at Hawthorn Hill for years and greatly admire its beauty, but we have no intention of propagating it ourselves for sale at our nursery.