Q.What is this.
Hey, I asked this a while back but have lost the answer.
This is fast growing, even when chopped down and also it spreads! Any ideas on what it is and how to kill it off?
Certified GKH Gardening Expert
Without any other identifying factors, it is very hard to say. This resembles several genus, and countless species within the genus.
I will give you my best guess based on the pictures and description.
I have pinned it down to a few Genus. Rhus, Sorbaria, and Sorbus. A sumac, false spirea, and quickbeam, respectively.
Getting rid of it will require you to dig it up, completely. Pouring boiling water on it a few times a day for two or three days will provide a quick death, as well. Other means will include herbicides, and chemicals, should boiling water fail. (It won't fail often)
This article will help: https://www.gardeningknowhow.com/plant-problems/weeds/using-herbicide-in-gardens.htm