Cassian has over 25 years of experience as director of Hermannshof Garden, a privately owned and internationally well known display and trial garden in Weinheim in South-Western Germany. Cassian’s role includes developing low maintenance and sustainable plant combinations using natural plant communities.

His research  has been focused on the 'New German Style' of planting, using stress tolerant natural plant communities  (mainly North American prairie and Eastern European steppe) as models for new sustainable plant combinations for the urban environment.

He is also profesor at Hochschule Geisenheim University.