Although this Japanese species is widely cultivated, there is only one record of a self-seeded plant: from JEFF (MM for WKY). There must be factors generally preventing its naturalization. The European T. baccata L. may also rarely establish near plantings, but there is no definitive evidence. CW noted a 2006 coll. of baccata from WHIT (EKY), but the label does not indicate any self-sown status: "woods edge, Resort Cabin Road" at Cumberland Falls State Park, where many alien shrubs have been planted since the 1930s. Identification of young plants is problematic, and there has been a need for better keys to all taxa (FNA 2, W; Pace 2015). These alien species (baccata, cuspidata) and the other North American species (western T. brevifolia Nutt., southeastern T. floridana Nutt.) together differ from canadensis as follows (based on preceding citations): shrubs or trees up to 6-25 m, usually upright (unless pruned) with a central stem and not spreading with rooted layers (versus sprawling shrubs up to 2 m, spreading with rooted layers); leaves 1-3 (4) cm long (versus 1-2.5 cm), the two bands of stomata on lower surface with mostly 8-14 stomata across each band-width (versus 5-9), and with papillae prominent between stomata (versus obscure). T. baccata may be distinguished from cuspidata by its bud scales (W): blunt, only slightly keeled (versus often acute, keeled).