noun
moss-rose purslane
A flowering plant (Portulaca grandiflora), also known as 松葉牡丹 (matsubabotan). The name アメリカソウ is rare; 松葉牡丹 is the more common Japanese name.
See also: 松葉牡丹
アメリカソウは、松葉牡丹とも呼ばれる園芸植物です。
Amerikasō is a garden plant also called matsubabotan (moss-rose purslane).
From アメリカ (America) + 草 (grass, plant). The name likely arose because the plant was introduced from the Americas.