By Bryon Walters
I have a corner in my prairie where a neighboring farm field drains through my center waterway. Sometimes I receive corn plants from the field, but for the past several years Giant Ragweed, Ambrosia trifida, has found a temporary home in the prairie.
It is not feasible or wise to spray this large canopy weed because there are many nice prairie plants growing next to or under them.
The best approach I like is the old fashioned clip method. With a sharp pair of shears I cut these tall weeds from the top down in sections, usually thirds or halves. I clip the few Mare’s tails also. Just leave the cut material lay there. They don’t grow back and I’ve observed less plants than last year.
It took me less than 30 minutes to cut up several hundred various sized “rags”.
This is very rewarding work and I don’t have to worry about damaging nice plants. If you have a larger infestation, you could use a powered brush saw that has the three-blade cutting head on it. Although, you may accidentally cut things you don’t want to and the saw is difficult to maneuver in a tall, rich prairie.
Either method is better than chemical treatment.
Swamp Milkweed and Monarch approved.
grassland restoration network 
I like Ambrosia sp. My understanding is that they are very productive for moths and butterfly larva.
Then again, I don’t suffer from allergies either, so…
Thanks for sharing your methods! Despite my affinity for them, yes, I will mow them down in year 1 or 2 prairie planting.
Hi, this Ambrosia is a noxious weed listed under the Illinois Noxious Weed Law. Technically, it should be eradicated everywhere it grows. Of coarse, it doesn’t. Many people really suffer from Ragweed allergies. Fortunately, there are plenty of other native flower sources for Moths and Butterflies. Thanks for reading our blog.