This data contains the strain and wind data collected for 21 trees in Wytham Woods, a mature temperate woodland in southern England, from September 2015 to June 2016. This data was collected in order to (a) extract the resonant frequencies of trees, (b) to estimate the critical wind speeds at which the trees would break and (c) to test a finite element model of tree-wind dynamics. The strain data was collected at 4Hz using two strain gauges per tree attached at 1.3metres on the trunk and approximately perpendicular to each other. The wind data provided were collected from the canopy walkway in Wytham Woods using a cup anemometer (Vector Instruments A100LK/5M) in winter and a Gill Sonic-1 in summer, the time resolution varies between these instruments. Local climate data, including long term wind data, are available from the Environmental Change Network (https://doi.org/10.5285/fc9bcd1c-e3fc-4c5a-b569-2fe62d40f2f5 or data.ecn.ac.uk). Full details about this dataset can be found at https://doi.org/10.5285/533d87d3-48c1-4c6e-9f2f-fda273ab45bc