I have mine planted where they can spread out & they now cover an area approx. 4' x 4'. They started as 6 plants & letting them drop the seeds for 2 years. I will probably have to split it up this fall. They can get quite high, I've had some get close to 4' with tons of blooms but mostly somewhere between 2 1/2' & 3 1/2' with blooms about 2 1/2"