As many volcanoes are densely vegetated, understanding of interactions between active lavas and trees is essential for robust hazard modelling. Tree moulds features generated when advancing lava engulfs and combusts trees are widely documented but have, to date, only been described qualitatively. More detailed, quantitative study of moulds will provide insights into the nature and significance of lava-forest interactions. Here, we present a unique characterisation of the chemical, textural and thermal interactions between lava and a tree (an Albizia), by considering a basaltic pāhoehoe lava flow that travelled 20 km through Hawaiian rainforest on Kilauea’s East Rift Zone between June and December 2014, reaching the village of Pāhoa. The dataset includes chemical analyses of lava (major, trace and volatile species), quantitative descriptions of lava textures (density, vesicle and crystal populations), and thermal analysis to fingerprint the devolatilisation and combustion of wood, together with the crystallisation of lava cooling around the tree. We use these results to construct a three-stage thermal model describing heat transfer between the lava and the tree, showing how the interaction facilitates combustion of wood and release of its volatile species (CO2 and H2O) into the lava, whilst triggering cooling, crystallisation and rheological stiffening of lava surrounding the tree. Chemical analyses reveal that the inflating pāhoehoe at the lava-tree-contact was strongly CO2-enriched (up to 1200 ppm), and a local transition occurs from a far-field isotropic vesicular texture to dense tree-proximal lava bearing elongated, pipe-like vesicles. Moreover, lava crystallinity indicates a cooling rate of ~70 °C min-1, well above expected cooling rates (10 °C min-1) for a pāhoehoe lava flow without the presence of trees. We conclude that the tree had a local and important cooling effect on the lava that could potentially moderate lava mobility at larger scale if tree density, trunk diameter and moisture content are opportune.