Holy cow, I just did a Google search, as I do about every plant I post, and I found almost nothing about this plant on gardening web sites. What I did find was many articles containing words like: invader, infestation, noxious weed, outlawed, banned, quarantine, etc. It seems that this plant has a severe negative impact on wetlands, killing all other vegetation and damaging the habitats of wildlife. Most states and provinces of North America have banned the sale, even of hybrids bred for gardening use.

Gee, this plant has been in my garden for at least 10 years. I would not have considered it an invader, but maybe it is not spreading because it is in a rather dry corner of the yard. Every spring I do find tons of seedlings growing around it but I just till them out. The butterflies absolutely adore its flowers. One thing I have always disliked about the plant though is that, even though the spikes grow very tall, it does not support itself and flops over. This summer I have a couple of spikes that are now taller than the garage roof, about 8’ tall. The only reason they are upright is because the clematis right next to it wrapped some of its tendrils around the stalks and is literally holding it up. All of the other stems are nearly laying down.

Any garden site that makes any mention of this plant recommends pulling it out to prevent the seeds from blowing to another area and potentially causing an infestation somewhere.

Wow, the things you learn when you post flower pictures !