There are no exceptions for cultivars, hybrids, or so- called sterile varieties. There are many native plants that have similar color, structure, height and blooming that can be used as alternatives to purple loosestrife in the garden. Any control method you select should be repeated for several years to catch missed plants and those reestablishing from seed. Be sure to get the entire root. Roots left behind will resprout.
Older plants are generally too big for pulling and are difficult to dig up.
Avoid excessive soil disturbance. If this is unavoidable, consider chemical methods. Removed plant parts should be bagged and placed in proper container for garbage pickup. Don't throw them in your compost pile. Mowing Mowing has not been found to be an effective way to destroy purple loosestrife unless the plants are cut below a level that water will cover for approximately 12 months.