Aconogonon nakaii

Koenigia weyrichii var. nakaii

Flower name
Aconogonon nakaii
Scientific name
Koenigia weyrichii var. nakaii
Alias御山蕎麦
Place of originendemic to Japan
Place of floweringHigh mountain
Flowering seasonJuly, August, September

What is Aconogonon nakaii

Koenigia nakaii

Koenigia nakaii commonly called Oyama-soba (御山蕎）in Japan, scientific name: Aconogonon nakaii, is a perennial herb of the genus Aconogonon in the family Polygonaceae, endemic to Japan.
It grows naturally in gravelly or rocky areas of alpine zones.

The plant reaches about 30 cm in height.
Its underground rhizomes spread, forming tufted clumps. The stems are thick, tinged with red, and well-branched.
The petioles are short, and the leaves are somewhat thick, ovate, 4–12 cm long and 2–5 cm wide, with an acute tip. The leaf margins are entire, and the leaves are alternately arranged.
It is monoecious, bearing both male and female flowers on the same plant.
From July to September, it produces numerous small flowers in racemes 4–5 cm long, with white sepals, 8 stamens, and a 3-cleft style.
However, what appears to be petals are actually the 5-lobed sepals, as petals are absent.
After flowering, it bears glossy brown achenes with three ridges.

Origin of the Name

The Japanese name “Oyama-soba” (御山蕎麦) comes from Oyama, meaning sacred or high mountains such as Mt. Hakusan, and soba because the flowers resemble those of buckwheat (Fagopyrum esculentum).
The specific epithet “nakaii” is a dedication to Japanese botanist Takenoshin Nakai.

Common name: Oyama-soba (御山蕎麦)
Scientific name: Koenigia nakaii
Sinonimus name: Aconogonon nakaii
Native range: Endemic to Japan
Habitat: Gravelly and rocky areas in alpine zones
Taxonomy: Order Caryophyllales, Family Polygonaceae, Genus Aconogonon
Height: 30 cm
Underground part: Rhizome
Growth form: Tufted
Stem: Thick, reddish, well-branched
Leaf texture: Somewhat thick
Petiole: Short
Leaf shape: Ovate, acute tip
Leaf length: 4–12 cm
Leaf width: 2–5 cm
Leaf margin: Entire
Leaf arrangement: Alternate
Sexuality: Monoecious
Flowering period: July–September
Inflorescence type: Raceme
Inflorescence length: 4–5 cm
Petals: Absent
Sepals: 5-lobed, petal-like
Flower color (sepal color): White
Number of stamens: 8
Style: 3-cleft
Fruit type: Achene
Fruit shape: 3-ridged
Fruit color: Glossy brown