I am working with a community garden and Ironweed is a major problem. Is there an organic product that will eliminate this problem?
The Gardener’s Answer
First, I have to commend you on being part of a community garden. These spaces are beneficial on so many different levels, and although the idea of community gardening is not new, it has certainly has made a come back in recent years. Like any garden, it can be rewarding and challenging at the same time. Ironweed (Vernonia) is a large group of tough plants. Some cultivars have been selected for home gardens and are especially popular in butterfly gardens, but other species can be troublesome and difficult to eliminate.
Ironweed was given this name for a reason; even with gardening tools it is difficult to remove the taproots and thick rhizomes of this plant. Eradicating it completely will be an ongoing project, but getting it under control is the first step.
Remove all foliage as soon as you notice any new growth. This will starve the plant of essential nutrients and prevent it from flowering and producing seed that will turn into more plants. When you turn your soil and prep it for planting, this is a great time to remove any willing roots.
Corn gluten meal and other organic pre-emergent products will prevent the Ironweed seeds from germinating, but it will also stop wanted seeds from sprouting as well. Spot spraying with vinegar and/or pouring boiling water can also be helpful with the taproots, but make sure it does not come into contact with other plant material in the bed. Studies that have been conducted to eliminate Ironweed have found that mowing in combination with herbicides did not eliminate this herbaceous perennial completely. Not to discourage you, but just to let you know what you are up against. A lot of elbow grease and persistence will pay off in this case.