Cocklebur - Onamomi

An annual plant of the Asteraceae family (APG classification: Asteraceae). It grows to about 1 meter in height. The leaves are alternate and have 3.5-10 cm stalks. The leaf blade is ovate-triangular with a heart-shaped base and has 3-5 shallow lobes. The texture is somewhat thick, with bristly hairs on both sides and roughness. The flower heads are unisexual, with the male flower heads growing in short panicles from the leaf axils, and the female flower heads growing in the leaf axils below the male flower heads. The male flower heads have a single row of involucre surrounding many florets. The florets have a tubular corolla. The female flower heads have two rows of involucre. The inner segments are fused together to form an oval body, and the surface is densely covered with hook-shaped thorns. The florets have no corolla. The fruit is called soujishi, and in China it is considered an important medicine indispensable for the treatment of sinusitis. It is also used to treat neuralgia and malaria. The involucre leaflets that encase the fruit are densely covered with thick glandular hairs that allow it to adhere to other objects. It grows in wastelands and on roadsides, and is widely distributed in the Northern Hemisphere. When young, it looks similar to Menamomi, but Menamomi has bisexual flowers and the fruit does not have thorns. The name comes from the fact that it is more hardy than Menamomi.

[Hiroji Koyama February 18, 2022]

It is thought to have been naturalized in Japan a long time ago. Its numbers have decreased nationwide, and it has become extinct in Tokyo and the Kansai region. Instead, the non-native species, cocklebur, and burrs, have increased in number, but the cocklebur is also decreasing in number.

[Editorial Department, February 18, 2022]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

キク科（APG分類：キク科）の一年草。高さ約1メートル。葉は互生し、3.5～10センチメートルの柄がある。葉身は基部が心臓形の卵状三角形で、浅く3～5裂する。質はやや厚く、両面に剛毛があってざらつく。頭花は単性で、雄頭花は葉腋(ようえき)から出る短い円錐(えんすい)花序につき、雌頭花は雄花序の下の葉腋につく。雄頭花の総包片は1列で、多数の小花を取り巻く。小花には筒状の花冠がある。雌頭花の総包片は2列。内片は合生して、卵円体となり、表面にかぎ状の刺(とげ)を密生する。小花には花冠がない。果実を蒼耳子(そうじし)といい、中国では蓄膿症(ちくのうしょう)の治療に欠かせない重要な薬物とされている。神経痛、マラリアの治療にも用いられる。果実を包む総包葉片に太い腺毛(せんもう)が密生し、これで他物に粘着する。荒れ地や道端に生え、北半球に広く分布。若いときの外観はメナモミに似るが、メナモミは両性花で果実には刺がない。名はメナモミより強壮であることによる。

［小山博滋　2022年2月18日］

　日本には古い時代に帰化したと考えられている。全国的に数が減り、東京や関西では絶滅した。かわりに外来種のオオオナモミやイガオナモミが増えたが、オオオナモミも減少しつつある。

［編集部　2022年2月18日］

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