Identifying and Removing Suckers on Grafted Knockout Roses

A North Carolina gardener had fast-growing green shoots from the base of Knockout roses. They'd been removing them as suckers, but were told they might be the Knockout itself. Also, Knockouts got black spot despite "disease-free" claims.

Sucker Identification

Grafted roses have a bud union bump. Shoots below the bump = rootstock suckers (Dr. Huey)—tear them off. Shoots above = the Knockout variety. Knockouts can grow fast too.

Disease Reality

Knockouts are disease-resistant, not immune. In favorable conditions (humidity, heat), they get black spot like any rose.