This dataset is the result of a survey conducted during the 2012-2016 COST Action FP1202 (MaP-FGR): Strengthening conservation: a key issue for adaptation of marginal/peripheral populations of forest trees to climate change in Europe. It contains the name, location and other relevant information of 577 forests that are considered as marginal of peripheral by forest experts. Information (as specified in the read-me file) includes among others: Genus, Species, Country, Name of marginal population, Latitude, Longitude, Elevation, Type of marginality, Silvicultural system, Protection status, Threat status, and genetic and phenotypic trait data availability This dataset can be used to, e.g., test effects of marginality on biological and genetic traits, compare expert knowledge with statistics-based indicators, raise awareness of the importance of marginal populations for conservation and sustainable use. Abies alba, Abies marocana, Acer monspessulanum, Acer obtusifolium, Acer opalus, Alnus cordata, Alnus glutinosa, Arbutus andrachne, Arbutus unedo, Betula pendula, Carpinus betulus, Castanea sativa, Cedrus brevifolia, Cedrus atlantica, Cretagus azarolus, Cupressus atlantica, Elaeagnus, angustifolia, Fagus sylvatica, Fraxinus angustifolia, Fraxinus excelsior, Fraxinus ornus, Fraxinus syriaca, Juglans regia, Juniperus deltoides, Juniperus drupacea, Juniperus phoenicea, Juniperus turbinata, Larix decidua, Picea abies, Pinus brutia, Pinus cembra, Pinus halepensis, Pinus heldreichii, Pinus mugo, Pinus nigra, Pinus peuce, Pinus pinaster, Pinus pinea, Pinus sylvestris, Platanus orientalis, Populus nigra, Populus tremula, Prunus avium, Quercus boisierri, Quercus calliprinos, Quercus cerris, Quercus frainetto, Quercus ilex, Quercus ithaburensis, Quercus look, Quercus petraea, Quercus pubescens, Quercus pyrenaica, Quecus robur, Quercus trojana, Salix alba, Salix phylicifolia, Sorbus torminalis, Ulmus glabra, Ulmus laevis, Ulmus pumila, Ulmus canecens.