Calystegia pubescens, commonly known as Japanese bindweed, is a species of bindweed (https://en.wikipedia.org/wiki/Calystegia_pubescens). This species is a weedy wildflower distributed in Japan, South Korea, and countries in south-eastern Asia. Bindweed or false bindweed (Calystegia) resembles morning glory (Ipomoea nil). Both are climbing plants. Yet, there are different characteristics. Ipomoea nil is the annual with different leaf shapes and has a typical tap-root system of dicotyledons while Calystegia pubescens is the perennial with specific leaf shapes and has an extensive root system of both vertical and lateral roots, including rhizomes (underground stems) and its seeds remain dormant in the soil for many years making it difficult to eradicate.
https://en.wikipedia.org/wiki/Calystegia; https://en.wikipedia.org/wiki/Calystegia_pubescens; https://en.wikipedia.org/wiki/Ipomoea_nil
Bindweed growing in the roadside next to a drugstore, Kofu, Yamanashi, 5/25/2025