I have a couple of Euphorbias that are horribly invasive here. E. cyparissias has seductively sweet honey-scented flowers in the spring, but spreads by underground runners all year long.. It gets into everything. Last winter I dug most of it up, but it has very fine roots that break off the main ones and re-grow. Here it is with 'Hello Darkness'
The other one is Euphorbia robbiae which is great for dry shade, but has spread like a mow foe
... A couple years ago I was digging some up that had spread into the gravel walk, and got some of it's sap in my eye. I was in agony and had to wait an hour for Dave to drive through traffic to take me to the Dr. The pain was right up there with childbirth.