obedient plant, or
Physostegia virginiana
Plant Family.......... Labiatae (Mint)
Plant Height .... 3 Feet
Leaf Arrangement..Opposite
Habitat.............Open Areas
Flower Color....Purple and white

Can be invasive in rich cultivated soils. I have some in a front bed at the border in front of black-eyed susans. Mine are white. They haven't spread too much because I keep the soil lean and a bit sandy. I do apply compost once in the spring and that is it. Like the black-eyed susans, they don't need too much water and bloom for about three weeks in my yard.

It started taking over a corner of one of our large beds and it has taken me five years to get rid of it! I dug out all our plants and sifted every grain of dirt in a 225 cubic foot area TWICE; not any fun!!!

They are pretty but obedient they aren't! I'd use them in an area where you couldn't care less if they took over or not. Otherwise, they are just as bad as Bermuda grass in your beds.