Simon's poplar ("P. simonii"), a native of northwestern China, is frequently planted as a shade tree in northern European cities. It is an attractive ornamental tree with whitish bark, and nearly rhombic, 6–10 cm long leaves which appear on the tree in early spring. Maximowicz' poplar or Japanese poplar ("P. maximowiczii") and the Ussuri poplar ("P. ussuriensis" = "P. maximowiczii" var. "barbinervis") are similar, occurring in northeastern China, Japan, Korea, and eastern Siberia; they have broader leaves. Another similar species is the laurel-leaf poplar ("P. laurifolia" from Mongolia), which differs from its relatives in narrower leaves shaped like a bay laurel leaf. Another putative member of this group is the Korean poplar ("P. koreana").