Survey of over 4, 500 monumental olive trees preserved on-farm in the northeast Iberian Peninsula, their genotyping and characterization

•We inventoried 4526 ancient olive trees preserved on-farm.•All olive trees catalogued have exceptional size (trunk circumference at 1.30 m above the ground more than 3.5 m).•‘Farga’ cultivar was predominant among the ancient olive trees studied.•Survey allowed us to identify 10 unknown genotypes.