Ironweed is a common name of 25 species of Vernonia which are native to North America. Many of these species are native to the midwest and southeastern regions. Some species are as short as 2′ tall, while others can reach 10′ tall! It is an upright plant with tough stems, in which it is named after.
Ironweed has large clusters of purple flowers in late summer for about a month long. It attracts many bees and butterflies. Once the flowers have turned to fluffy seeds, it is actually very pretty in the fall garden.
It is an ecologically important plant and naturally you will often see it growing in unmowed fields and roadsides, marshes, thickets, and meadows. It is a host plant for the American Lady butterfly and the Crossline Skipper. Its nectar and pollen is attractive to many bees and butterflies.
Growing Conditions: Common ironweed (Vernonia fasciculata) likes full sun with moist soils. It can grow in average soil and tolerate brief flooding. It may be a good choice for a rain garden. It is deer and rabbit resistant, so also a good choice if you live in more rural areas.
Maintenance: Ironweed can be an aggressive seeder, so I usually cut off the seed heads before they fall to the ground. If you want to make the plant shorter, you can cut the plant back by 1/3 to half in June. This should still allow it to flower in the fall.
Ironweed is mostly susceptible to rust fungus. There is not much you can do to prevent this disease. You can dust plants with sulfur or spray need on them throughout the season. These act as a preventative, not a cure. You must be careful about any product that may harm insects if they come in contact with it.
There are some cultivars of ironweed sold in nurseries. ‘Iron Butterfly’ grows to about 3′ tall which makes it a good choice for a small garden.