Hello Vickie.......................
Even though it isn't used much in residential gardens it is often used in commercial landscaping. Our experience tells us cutting stems down to a third their height in late winter goes a long way toward controlling height.
I usually dig and pot up those root suckers I cannot use. My neighbors are only too happy to receive them as a gift. That tends to control spread.
These methods give us adequate control out here on the Great Plains. I do not know how well they would work in a milder climate like yours.
