For gardeners whose property borders a non-forested natural area, use the sterile or low fertility cultivars or remove the seed heads in the fall before they open. Many of the modern cultivars of Buddleia davidii have dramatically reduced fertility and are not invasive. Some hybrid cultivars (such as Buddleia 'Blue Chip') are almost completely sterile and pose no threat. Some low viability selections include Buddleia weyeriana, Buddleia fallowiana, Buddleia hemsleyana, Buddleia longifolia, Buddleia macrostachya, and Buddleia nivea.
From:
http://www.plantdelights.com/A...
AND from our own NGA:
http://garden.org/learn/articl...
