Calystegia hederacea aka Japanese False Bindweed

Calystegia hederacea is a vine in the Convolvulaceae family. It is perennial, so it lives for more than one growing season. Common names include Japanese false bindweed and Californian rose. Kew gives its native range as Ethiopia and Afghanistan to Japan. It grows in temperate regions. It is not native to Britain or Ireland. In central and southern Japan, it grows in sunny grassland and thickets. It grows in these sites in both lowlands and hills.

The plant climbs and can reach 16.4 feet [5 metres]. Plants For A Future lists its bloom time as August to October. Each flower has both male and female organs. Bees, moths, and butterflies pollinate the flowers, moving pollen between them. The supplied sources do not state the flower colour. They give no details of the fruit, either. Nor do they describe the leaf shape or stem traits.

Plants For A Future says this vine is easy to grow. It accepts ordinary garden soil and needs a sunny spot. The same source says it cannot grow in shade. It prefers moist soil and can grow in sand, loam, and clay. Soil pH can range from mildly acid to mildly alkaline. The listed USDA hardiness range is zones 4–8. Its climbing form adds interest to gardens, but plan for its spread. The growing notes warn that plants can become invasive. A separate entry says it has no weed potential. These two claims conflict.

Plants For A Future lists leaves, roots, and shoots as edible parts. Its notes describe cooked roots and cooked young shoots. The roots need cooking, washing, and steaming before use. They hold starch and sugar. But the source warns against eating them regularly. It reports no known cases of toxicity for this species. Still, it urges care, as related plants can have purgative effects. This means they can make the bowels empty. That does not prove this species is harmless. The source also notes a traditional use of seeds. People simmer them in water for diuretic use, to increase urine flow.

Grow new plants from seed, or divide dormant plants in early spring. Sow seed in spring under a cold frame. Cover it only lightly, and use compost that drains well. Seeds may take one to three months to sprout at 15°C. Keep seedlings in separate pots under cover through their first winter. Plant them out in late spring or early summer, once frost risk passes.