In 1983 and 1984 field plot experiments were established to assess the effects of a foliar applied (2 or 4L ha−1×four applications per season) kelpMacrocystis integrifolia, concentrate on growth and nutrition of bean,Phaseolus vulgaris. A commerical kelp concentrate, prepared fromEcklonia maxima, was also used as a test comparison. In the first year a phytohormonal extract of theM. integrifolia concentrate, designed to extract the cytokinin, auxin and gibberellin phytohormones, was also applied to the crop to test the thesis that these phytohormones are active constitutents. In each of the two field seasons the kelp concentrates increased harvestable bean yields on average by 24%. The phytohormonal extract also increased yields, but was less effective than the kelp concentrate itself. Bioassay results demonstrated the presence of phytohormone-like substances in this crude extract.