Through field experiments conducted at three locations over several years I sought to determine the effect of B and lime on crop yields and tissue B concentrations in alfalfa (Medicago sativaL.), red clover (Trifolium pratenseL.), and timothy (Phleum pratenseL.). Boron applications increased alfalfa yields by 8 to 32% in half of the cuts and red clover yield by 15% in one cut at one location only. Liming proved to be most important for increasing yields of alfalfa, red clover, and timothy in that order. Tissue B concentrations of less than 30 ppm in alfalfa and of less than 20 ppm in red clover were related to B deficiency symptoms (yellowing of young leaves and tops in alfalfa and reddish coloration of young leaves in red clover). I found timothy to be insensitive to B deficiency; tissue B concentrations as low as 4 ppm were not related to any B deficiency symptoms on the foliage. Tissue B concentrations of 108,92, and 95 ppm in alfalfa, red clover, and timothy, respectively, were related to B toxicity symptoms on the foliage in the form of burning of older leaf edges, but were not related to any appreciable yield decreases. Large decreases in B concentrations occurred between the first and second samplings in B-treated samples. Liming decreased the plant tissue B, most decreases occurring in the earlier samplings. The results indicate that applying 2 kg B/ha should maintain sufficient B for alfalfa and red clover for 2 years.