Frost stress is the main factor determining the distribution of plants at high latitude and elevation. Although species are currently adapted to their highest location, climate change is likely to modify their adaptation strategies in the face of climatic stress. This is particularly true for trees at their altitudinal limit, where the number of freeze-thaw episodes is likely to increase. To monitor the exposure to frost stress and its impact on tree growth, we monitored five contrasted species (Acer pseudoplatanus, Betula pendula, Larix decidua, Picea abies and Sorbus aucuparia) over a 3-year period in the Lautaret alpine garden (2100 m asl) by using an automatic, autonomous, connected micro-dendrometer. These systems continuously measured (every 30 minutes or 1 hour) both variations in trunk diameter and air temperature in the vicinity of the measurement, making it possible to determine the number and duration of frost cycles, growth periods and ecophysiological functioning of the species monitored in these extreme conditions. We observed specific responses of the trees, in relation to their wood anatomy and leaf phenology