The linden genus (Tilia spp.) is a group of mostly trees native to the northern hemisphere in North America, Europe, and Asia composed of approximately 30 species. As a group of broadly adapted trees, lindens are planted in municipal forests around the world along streets and in parks. Species are known to be somewhat difficult to identify due to the consistently shared morphology of the foliage and flowers as well as notable variation on a single specimen. Additionally, species are capable of hybridization when overlapping in distribution. Ploidy variation within the genus has been reported in the literature as both diploids (2n=2x=82) and tetraploids (2n=4x=164). In order to better understand relationships among species, ploidy should be known. Flow cytomery can be used to determine ploidy and relative genome size. The Morton Arboretum Plant Collections Network accredited Tilia collection includes 58 unique taxa representing 24 species from around the world. The current study uses flow cytometry with the fluorochrome DAPI and Pisum sativum 'Ctirad' as the internal standard to determine ploidy in wild and cultivated lindens. Information from this study can and will be used to inform the development of a genus phylogeny as well as applied in breeding programs.
