What is this plant?

This is a plant that was given to me. It was in a 2" pot for two years. Since it didn't die, I planted it. It's now about 3' high and very root invasive. I dug it out from where I first planted it because it overtook what was there, but it is back as big as it was. The original one that I dug out is in a large pot and doing well. It's a pretty thing, and as long as it stays in the pot, I'm happy with it. I needed to raise the pot off the ground to keep it contained, however, since it rooted below the pot!
Anyway... I'd like to know what it is. A friend said she thought it was an herb, but I don't remember which one, and she wasn't sure. I took it to my local nursery. They are looking, but they're not sure either. They thought it may be a variety of polemonium. When I looked for polemonium the internet, nothing I got really looked like this. Lots of similar flowers, but not with similar leaves.
Height: about 3 feet, perhaps a bit more
Leaves: Kind of scratchy feeling, but not thorny. Those at the base of the plant are larger than my hand. Near the top they are about 2".
Light: Seems to prefer shade to semi-shade
Water: Needs regular good watering and more frequently when in the sun or it flops over.
Flowers: Lavender color in clusters at/near the top of the stems. No scent that I was able to discern. Starts blooming in late May, here in Oregon. I think it kept blooming lightly through the summer, but I am not positive about that.
The plant dies away above ground completely in the winter.
TIA
~Faith