Vernonia lettermannii - Ironweed

Vernonia lettermannii is a wild vernonia native to Arkansas, a perennial plant that hides great robustness under its graceful appearance. It forms a large clump of stems adorned with very fine foliage and displays numerous inflorescences composed of fine, tousled aster flowers in a beautiful purple colour at the end of summer. North American vernonias are relatively underused, charming plants, highly resistant to cold, and easy to grow in sunny locations with good, slightly moist soil in summer. Just like asters, which bloom at the same time, they are excellent plants for flower beds.

Vernonia lettermanii belongs to the Asteraceae family. This species is found in the central west of Arkansas and neighbouring Oklahoma. Its natural habitat consists of gravel banks found along watercourses as well as adjacent rocky outcrops in dry to occasionally flooded areas. It is a herbaceous perennial plant anchored by a strong taproot that will reach 1m (3ft) high and occupy 1.20m (4ft) of ground space without being invasive. Its growth rate is moderate, taking two years to establish, but it has a long lifespan. This vernonia forms a large clump of straight and sturdy, unbranched stems, carrying alternate, simple, thread-like, dark green leaves up to 7.5cm (3in)  long. From August to September-October depending on the climate, it has lots of violet, 2.5cm (1in) wide flower heads, gathered in terminal corymbs at the ends of the stems. The flowers all open at the same time, attracting a large number of butterflies for a magnificent spectacle. The deciduous vegetation emerges in spring and dies in winter.

Vernonia lettermannii is very easy to grow and blends well with a multitude of plants to form magnificent autumn compositions with asters, shrubby salvias, masterworts, heleniums, and vervain hastata, for example. In a wilder style, at the back of a flower bed, this imposing perennial forms a very successful combination with Rudbeckia maxima and tall grasses such as Miscanthus 'Malepartus', Panicum, Stipa...