Tansy vulgare is VERY drought tolerant! It's one of our most common weeds in dry Eastern Washington. It's a common weed of dry abandoned lots, roadsides, ect. I keep one for attracting Ladybugs and use the flowers and leaves as a mice deterrent in fall; just scatter leaves and flowers about around the house under cabnits, in attics, ect.
They do form a colony, but it's quite slow where it's kept dry. To prevent numerous volunteers, remove all seed heads when they start to fade. Plants can grow to about 6' tall and half as wide.

Vera

Wonderful--thank you, Vera!