I've been scouring the internet for weeks on this and am hoping for some help.
This plant is growing prolifically in a flower bed in my yard starting in late April. Below are three pictures of single stalk that I pulled up (I think this is a mature version of it at 2+ feet with serrated leaves and a cluster of small white flowers on the top).
This plant appears to grow through rhizomes based on my experience in pulling it up although it's possible that it's just so well-seeded that it appears as though the clumps are connected. The stems pull out of the ground easily but tend to break off at the root making it very hard to weed. Only a few have survived to the flowering stage you see above (due to intensive weeding efforts), but even before flowering, they can grow more than two feet tall and are shading and crowding out some sedums and lillies that did not emerge as quickly (which is why I'm designating it as a weed because it's aggressively crowding-out wanted plants). Additionally, I think I've come to the conclusion that I have a variegated version of this growing in a different part of my yard.
- Location: Illinois
- 2-3 feet tall
- Serrated, opposite leaves
- Small, clustered white flowers
- Fast growing (possibly via rhizomes?)
- Prolific (not uncommon to have 5-10 growing in a 1 to 2 inch area)
- Hollow stems
- Variegated variety exists
Picture 1: Entire Plant
Picture 2: Leaves
Picture 3: Flowers
Additionally, if you are familiar with it, any insight into controlling it would be greatly appreciated. Thank you!