Arisaema negishii

Arisaema negishii belongs to the arum family, Araceae. This perennial grows from a tuber, a part below ground that lives from year to year. Its native range includes South Korea and Japan’s Izu Ōshima. Kew lists it as a plant of temperate climates. The RHS confirms it is not native to Britain or Ireland. The records give no height or spread for full-grown plants. They give no leaf or stem details for this species.

Plants For A Future calls this species dioecious. This means male and female flowers grow on separate plants. Both sexes must grow together for the plants to set seed. Flies carry pollen between flowers. The plant cannot use its own pollen to form seed. The records do not state which months it blooms. They give no fruit details for this species. The RHS describes flower parts for the genus as a whole. This does not show this species’ exact flower shape or colour.

The species entry lists sand and loam as suitable soils. Soil should stay moist but let excess water drain away. The listed pH range is mildly acid to mildly alkaline. PFAF says it can cope with sun, part shade, and full shade. Its landscape notes favour dappled shade or a shady edge. These notes do not favour deep shade, though other notes list wider shade tolerance. The evidence does not confirm that it withstands British winters. PFAF marks its further growing advice as guidance for the genus.

PFAF advises sowing fresh seed in a shaded cold frame. Stored seed can stay viable for at least one year. Seed sown in spring may need cold before it sprouts. Seeds take one to six months to sprout at 15°C. Keep young plants in pots under light shade for two years or more. The entry says to plant them out while dormant, when growth rests. It also lists a way to grow more plants from tubers. Divide them after the growth dies back in late summer.

The plant has calcium oxalate crystals. These can hurt the mouth and tongue. PFAF lists the root as edible only after preparation. It describes boiling and peeling the root. It warns not to eat the root raw. This food-use record does not mean the untreated plant is safe. The source reports no known uses as medicine or for other purposes. It also lists no risk of becoming a weed. The evidence gives no pest or disease account for this species.