This paper presents the results of long-term remote monitoring of tree overgrowth on abandoned agricultural lands. This monitoring is based on multi-temporal satellite images with ultra-high spatial resolution and highly-detailed optical survey from Unmanned Air Vehicles (UAVs). Successful use of photogrammetric dense point clouds was demonstrated for three-dimensional reconstruction of tree canopy structure on abandoned agricultural lands by using the tree canopy height digital model. Spatial data were obtained on tree expansion on the fallow in 2005-2018, current tree canopy heights and its vertical growth, stem density, and canopy closure. The study revealed distinct spatio-temporal heterogeneity of tree overgrowth on the fallow. In the first years after land abandonment the most rapid regeneration and dispersal of trees occurred from the forests resulting in very dense but low tree cover adjacent to the forest. Later, tree overgrowth occurred in isolated hotspots and was characterized by very intensive vertical growth of the tree canopy.