 A small workshop produced pendulums for dowsing and a line of negative ion generators.With the buildup of the vitamin business surrounding discoveries that spirulina had significant weight loss benefits University of the Trees became one of the largest employers in the San Lorenzo Valley and leased more than 10 buildings in Boulder Creek for housing students and warehousing for Light Force, a burgeoning nutritional products brand based on spirulina.From this base in California, Hills extended his hospitality to a pantheon of visiting scientists, writers, philosophers and scholars such as Alan Watts, Edgar Mitchell, Barbara Marx Hubbard, Allen Ginsberg, Thelma Moss, Hiroshi Motoyama, Haridas Chaudhuri, Sri Lanka president Ranasinghe Premadasa, Menninger Foundation's Swami Rama, Dr. Evarts G. Loomis, Viktoras Kulvinskas, Max Lüscher, Marcia Moore, Bernard Jensen and countless others in the fields of human potential, holistic health, aquaculture, religion, quantum physics and alternative medicine.