This dataset reports metrics of plant growth, including height, total biomass and the biomass of component plant parts, and percentage root colonisation by mycorrhizas, for tree seedlings of eight tropical and seven subtropical growing in pots of soil that had been amended by addition of various sources of phosphorus (inorganic phosphate, adenosine monophosphate, phytic, or a mixture of all three) plus an unfertilized control treatment with no P additions. The aim of the experiment was to test the hypothesis that seedlings of species that associate with different types of root-inhabiting mycorrhizal fungi would respond differently to the range of P sources applied in the experiment. The experiments were conducted as part of a NERC Discovery Science project with the title Explaining niche separation in tropical forests: feedbacks from root-fungal symbioses and soil phosphorus partitioning led by Professor David Burslem (University of Aberdeen) reference NE/M004848/1. Full details about this dataset can be found at https://doi.org/10.5285/3ad644c9-e341-4a15-ab35-311076defc33