The Siebold's spurge (Euphorbia sieboldiana) belongs to Euphorbiaceae (the Spurge family). It is a perennial herb that is native to various parts of Japan and the Korean Peninsula. This herb grows in mountains and hills and can reach 20-40 cm in height. The cauline leaves are alternate, oblanceolate to narrow elliptic, and 4-5 arranaged in whorls at the tip of the stem. It is a poisonous plant and the white saps ooze when the branches or leaves are injured. The cyathia are borne on the five branches of the shoot apex from April to June. The four glandular bodies of the cyathium are crescent-shaped, pointed at both ends, dark reddish purple, and produce nectar. The flowers bloom on two triangular bracts.