Isodon longitubus

Isodon longitubus belongs to the mint family, Lamiaceae. Its common name is trumpet spurflower. This perennial lives for more than one growing season. It comes from southeastern China and central and southern Japan. Records from China name the provinces of Anhui and Zhejiang. In Japan, it grows in the mountains. In China, it grows by streams in forests. These sites reach about 3,610 feet [1,100 metres] above sea level. It is not native to Britain or Ireland.

The plant grows upright to about 3.3 feet [1 metre]. The sources give no mature width or wider height range. They give few details about its leaves and stems. The RHS lists two older names for this species. One is Plectranthus longitubus. The other is Rabdosia longituba. These names may help when you check older plant records. The plant comes back each year. It does not complete its life in one season.

Chicago Botanic Garden records purple blooms in September and October. The flowers thus appear late in the garden year. Each flower has both male and female organs. The records do not say what pollinates the flowers. They do not describe the fruit or seed. Chicago Botanic Garden lists the plant for screens and hedges. Plants For A Future suggests woodland edges and patches of shade. Its upright shape and fall blooms suit these garden uses.

Grow it in moist soil with moderate watering. Chicago Botanic Garden lists a site in full sun. Plants For A Future says light shade also suits it. It can grow in sand, loam, or clay soils. Soil can be slightly acid, neutral, or slightly alkaline. Chicago Botanic Garden gives USDA hardiness zones 6–8. Plants For A Future has little direct proof of British hardiness. It thinks the plant may grow outdoors there, but remains unsure. The sources give no firm UK hardiness rating.

Plants For A Future lists cooked leaves as a famine food. This means emergency use, not advice to eat them as routine food. It gives the plant a low edible-use rating. It reports no known hazards. This does not mean the plant is safe for pets. It lists no known uses for medicine or other purposes. It does not flag the species as weedy. The records give no details of specific pests or diseases.