A 3 pine bark: 1 peatmoss: 1 sand (by volume) medium was amended with 7.7 g P as superphosphate, triple superphosphate, ammonium phosphate, or controlled-release ammonium phosphate per 1000 g medium (3.8 liters). The medium was then leached with 250, 350, or 450 ml distilled, deionized water daily for 25 days. Phosphorus leaching curves were then generated for each fertilizer. A subsequent study determined the effect of these four P fertilizers on growth of marigold seedlings in the greenhouse. Superphosphate, triple superphosphate, and ammonium phosphate rapidly leached from the medium, while the controlled-release ammonium phosphate was retained for a longer time. Marigold growth was not affected by fertilizer type; however, marigolds grown in P-amended media were larger than those grown without P. These studies indicate that amending container growing medium with superphosphate or triple superphosphate prior to planting may not be cost-effective.