わが国の各地をはじめ、朝鮮半島や中国に分布しています。明るい草原に生え、蔓性で他のものによじ登ります。葉は鉾形から鏃形で、長い葉柄があります。葉の基部にある耳状の部分が斜め後方に張り出し、また「こひるがお」のように分裂しないことが特徴です。6月から8月ごろ、葉腋に直径5〜6センチの淡い紅色の花を咲かせます。しっかりした地下茎があり、畑の雑草になっています。中国語では「柔毛大碗花(rou mao da wan hua)」と呼ばれます。
ヒルガオ科ヒルガオ属の多年草で、学名は Calystegia japonica (syn. Calystegia pubescens)。英名は Japanese bindweed。
The Japanese bindweed (Calystegia japonica) belongs to Convolvulaceae (the Bindweed family). It is a perennial herb that is native throughout Japan, as well as the Korean Peninsula and China. This herb grows in sunny grasslands, and twines around other plants. The leaves are hastate to arrowhead shaped with long petioles. It is characterized by the oblique backward protrusion of the ear-like portion at the base of the leaf and also by the fact that it does not divide as in the "Ko-hirugao". The flowers are pale rose pink, 5-6 cm across, and bloom on the axils from June to August. It has firm rhizomes and is a weed in the field. In Chinese, it is called "柔毛大碗花" (ju mao da wan hua).