Acer palmatum, called Japanese maple or smooth Japanese maple (Japanese: irohamomiji, or momiji) is a deciduous shrub or small tree (generally 6–10 m tall) with low branches and a rounded to dome-shaped crown, native to Japan, North and South Korea, China, eastern Mongolia, and southeast Russia (Wikipedia 2011). Hundreds of cultivars are grown around the world as an ornamental and specimen tree for their dramatic leaf shapes and colors, and are widely used in bonsai.

Development of cultivars started in Japan in the 1700s, where patient and discerning gardeners selected and bred or used grafting to propagate attractive variants in leaf lobing, toothing, leaf color (ranging from yellow to green to red, purple, and bronze), and bark color, as well as overall size and form as a tree or shrub (Vertrees and Gregory 2009). There may be more than 1000 varieties and cultivars, including hybrids or grafts with closely related species, such as A. duplicatoserratum, A. japonicum (downy Japanese maple), A. pseudosieboldianum (Korean maple), A. shirasawanum (fullmoon maple) and A. sieboldianum (Siebold's maple). At least 350 cultivars are used in Europe and North America (Vertrees and Gregory 2009). In addition, the term “Japanese maple” may be used to refer to any of the 23 species of Acer that are native to Japan, which leads to greater variation of trees sold commercially as Japanese maples (Vertrees and Gregory 2009),

Acer palmatum has opposite, palmately lobed leaves, 4–12 cm long and wide, with five, seven, or nine acutely pointed finger-like lobes. The flowers are produced in inconspicuous small cymes, the individual flowers with five red or purple sepals and five whitish petals. The fruit is a pair of winged samaras (nutlets with stiff, fibrous, papery wings that aid in wind dispersal). Each samara 2–3 cm long with a 6–8 mm seed (Wikipedia, 2011).

Acer species, including A. palmatum, are variously classified in a family of their own, the Aceraceae, or are included together with the Hippocastanaceae in the family Sapindaceae. Modern classifications, including the Angiosperm Phylogeny Group system, favor inclusion in Sapindaceae (Wikipedia 2011).

Acer palmatum was named by Swedish doctor-botanist Carl Peter Thunberg, who traveled in Japan in the late 1700s and returned with drawings of this small tree. He gave it the species epithet “palmatum,” after the hand-like shape of its leaves. Japanese gardeners referred to this group of maples as “kaede” and “momiji,” referring to “frogs’ hands” or “babies’ hands,” (Arbor Day Foundation 2011).