シャクチリソバの花

桂川の河川敷で、ここ3，4年の間に急激に生息域を広げてきた植物の1つにシャクチリソバ(Polygonum cymosum)があります。シャクチリソバはユーラシア大陸に広く分布するタデ科の植物で、その名の通り、花も実も食用にされるソバによく似ていますが、えぐみが強くて食用にはなりません。解熱などの薬効があるということで、日本には明治時代に薬用植物として持ち込まれ、逸出して繁殖し、帰化植物として繁茂しています。アレロパシーにより他種の植物を駆逐するため、この季節になると、河川敷のあちこちにシャクチリソバの白い花の群落を見ます。ここでは、セスジハリバエの一種（？）が吸蜜に訪れています。

One of the plants that has been rapidly expanding its habitat along the banks of the Katsura River over the past three or four years is Shakuchirisoba (Polygonum cymosum). Shakuchirisoba is a member of Soba, the buckwheat family that is widely distributed in Eurasia. As its name suggests, its flowers and fruits are similar to those of buckwheat, which is used for food, but it has a strong acrid taste and is not fit for food. It was brought to Japan in the Meiji era (1868-1912) as a medicinal plant for its antipyretic and other medicinal properties, and then it has proliferated as a naturalized plant. Because of its allelopathic effect on other species of plants, there are colonies of white flowers here and there along riverbeds during autumn.

Here in this picture we see a fly visiting the flowers of Shakuchirisoba.

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