Chelonopsis Lamiaceae
An unusual and decidedly underused Japanese member of the mint family, Chelonopsis yagiharana forms an upright, clump-forming perennial with slender, often slightly purplish stems and handsome, toothed, dark-green leaves. From late summer into autumn it produces tubular, purple-pink flowers, held singly or in small groups towards the upper part of the stems. The flowers are remarkably long and narrow, giving the plant something of the appearance of a rather exotic Chelone — although botanically the two belong to quite different families.
Growing to around 40–60cm, it is an excellent plant for the late-season border, particularly in light woodland or the dappled shade of deciduous shrubs. It appreciates a fertile, humus-rich soil that remains reasonably moist but is not waterlogged. Once established it slowly increases by its rhizomatous rootstock rather than behaving like an enthusiastic thug.
It is a plant of mountainous valleys, woodland margins and forest edges, rather than open lowland ground. The species is considered uncommon in Japan; for example, the Ehime Red Data Book treats it as Endangered (EN) in Ehime Prefecture, where it is known from scattered localities including the Ishizuchi mountain system.
Its known distribution therefore centres on the Pacific side of central Japan, with the species occurring in a relatively small number of mountain localities rather than across Japan as a whole.
The species was described in 1918 by Hisauti and Matsuno, based on Japanese herbarium material collected in the preceding years. A particularly interesting account from the Kanagawa Museum records specimens collected by Yagihara Densaburo at Lake Shojiko in 1915, followed by material collected on Mount Ashitaka in 1917. The species was named in honour of Yagihara, whose name is preserved in the specific epithet yagiharana.
The accepted name is Chelonopsis yagiharana Hisauti & Matsuno. It has also been treated as Chelonopsis moschata var. lasiocalyx, but Kew currently recognises C. yagiharana at species rank.
The Japanese name is ashitaka jakōsō (アシタカジャコウソウ), referring to Mount Ashitaka and its relationship to the Japanese jakōsō — “musk-scented herb” — name used for Chelonopsis. It belongs to the Lamiaceae, the mint family.
Although still uncommon in cultivation, C. yagiharana is sufficiently hardy for Britain; Missouri Botanical Garden gives it USDA Zones 5–9, and recommends full sun to part shade, organically rich soil and moderate moisture.
Height: 40–60cm
Spread: 30–45cm
Flowering: August–October
Aspect: Sun or light/dappled shade
Soil: Moist, fertile, humus-rich and well drained
Hardiness: Approximately H5, and probably considerably tougher than its rarity suggests
A splendid late-season Chelonopsis for the collector of plants that make visitors ask, “What on earth is that?” — which, in our experience, is usually a very good reason for growing it.
