70 Species of grasses family (Poaceae), coming from genera: Agrostis, Alopecurus, Anthoxanthum, Apera, Arrhenatherum, Avena, Brachypodium, Briza, Bromus, Calamagrostis, Corynephorus, Cynosurus, Dactylis, Danthonia, Deschampsia, Digitaria, Echinochloa, Elymus, Eragrostis, Festuca, Glyceria, Helictotrichon, Hierochloe, Holcus, Hordeum, Koeleria, Leymus, Lolium, Milium, Molinia, Nardus, Panicum, Phalaris, Phleum, Phragmites, Poa, Saccharum and Setaria were fingerprinted on thin-layer chromatography (TLC) with densitometric scanning. Almost all species were collected from natural stands in Poland during the 2020 season. Chromatography was performed on silica gel F254 plates using ethyl acetate–methanol–water (8:2:2, V/V/V) in sandwich mode. Densitometric scanning was performed at 210, 254, 312 and 366 nm in extinction mode, as well as in fluorescence mode with 312/370, 366/420 and 366/550 nm of excitation and emission filter, respectively. Data fusion of the above seven modes of scanning was investigated chemometrically to check the redundance and amount of information in each mode. Principal component analysis (PCA) allowed to identify and interpret six orthogonal trends in phytochemical composition. As the data were hard to compress with PCA and the first six PCs explained only about half of variance, hierarchical cluster analysis (HCA) was used to divide the investigated species into five phytochemical classes. Interesting spots, which were omitted by PCA and HCA, were found by k-means clustering and visual inspection.