The vegetation of four different forest soils in lysimeters was killed with glyphosate. New vegetation became established in some of the treated lysimeters the year after application. During this year, leachates from lysimeters without vegetation had nitrate concentrations up to 4.5 mM NO3−in the fall. A corresponding increase in leached cations was evident. The settlement of one raspberry or one willow herb in treated lysimeters effectively hindered nitrate leaching as soon as the plants were sufficiently large (in mid‐summer). As plants became established in treated lysimeters, the chemistry of these leachates approached those of untreated lysimeters. The absolute effect of even small plants in controlling water regime and water chemistry was evident.