(Upload on Sept. 27 2007. Last on November 16 2016) [ 日本語 | English ]

Polygonum longisetum Bruijn

Mount Usu / Sarobetsu post-mined peatland
From left: Crater basin in 1986 and 2006. Cottongrass / Daylily

Polygonum L. (タデ)
Inutade (イヌタデ, 犬蓼), bristly lady's-thumb, (Asiatic) smartweed, bristled knotweed, bunchy knotweed or long-bristled smartweed
Akamamma (アカマンマ)
Lifeform: weedy annual forb (with 10-50 cm in height, occasionally 60 cm in height)
Distribution: widespread in Asia
Habitat: bareground - grassland
Seed germination: developing seasonality (Tsuyzuaki 2006), increased by cold stratification after smoke treatment (Tsuyuzaki & Miyoshi 2009)
Seedbank: persistent → developed in the former topsoil on Mount Usu (Tsuyuzaki 1989)
Flowering: during July and October in and around Sapporo

Persicaria longiseta (Bruijn) Kitag.

f. albiflorum (Honda) Ohwi (シロバナイヌタデ)
Additional record:
close to Kanda River, Tokyo, on December 17 2016

Polygonum longisetum in Japan

[1/2] at Hokkaido Univesity Campus. [1] on September 19 2007. [2] on September 16 2014. [3] at a grassland in Yushima Temple (seido), Tokyo, on May 30 2014. [4] beside a ground for elementary school in Muroran City on September 8 2014.
[5] in the campus of Hokkaido University of Education at Hakodate, southern Hokkaido, on September 26 2014. [6] at the foot of Nishiyama Craters on Mount Usu (有珠山) on September 9 2009. (also, recorded on August 27 2021). Annual plants must produce flowers within a given year. This plant was so small. This species developed a seedbank (埋土種子) in the former topsoil even 10 years after the 1977-78 eruptions on Mount Usu. [7] at the backyard of Toya Lake Experimental Station on September 13 2016. Records: on a trail adjacent to Toyonaka Park along Shojin River, Sapporo, on September 18 2021.