Calystegia silvatica aka Great Bindweed

Calystegia silvatica is also called giant bindweed. This vine climbs and lives for more than one year. It belongs to the morning glory family, Convolvulaceae. Its native range runs from the Mediterranean to northern Iran. It is also native to southern China. In North America, its range starts in southern Canada. It reaches as far south as northeastern Mexico. Kew places it in climates with mild heat and cold. It is not native to Britain or Ireland. Its older name is Convolvulus silvaticus.

This vine grows fast, reaching about 10 feet [3 metres] long. Its stems coil around supports, turning counterclockwise. Rhizomes, or stems below ground, help it spread. They let it grow past its first planting spot. The green stems hold white latex. Its green leaves are simple, with one blade each. They grow in turn along the stems. Their pinnate veins branch from a main vein. The edges are smooth, and most surfaces lack hairs. Leaves range from a triangle shape to an egg shape. Their bases have a deep heart shape. Each leaf tapers to a pointed tip. Leaves reach about 0.17–0.58 feet [0.05–0.18 metres] long.

Large flowers grow singly from May through August. Each looks like a trumpet and is mostly white. Blooms in the sun may show a pale pink tint. Each flower has five sepals and five stamens. The sepals sit around the flower. Large bracts overlap below it. These help tell it apart from hedge bindweed, Calystegia sepium. Giant bindweed has larger flowers than that plant, too. In fall, it forms small, round, brown capsules. Bracts hide these fruits, each of which holds four seeds. Each capsule splits open when ripe.

Grow it in full sun or part shade. It accepts clay, loam, and sand soils that drain well. It suits moist ground but copes with dry spells. Once it takes root well, it can withstand drought. NC State lists it for USDA zones 3–10. Its stems can climb trellises, walls, and other upright supports. Its flowers suit cottage-style gardens. Yet its strong spread makes it hard to manage. NC State lists seed and division as ways to grow new plants.

Giant bindweed grows in woods, fields, lawns, and disturbed ground. It has escaped gardens in parts of the United States. It spreads with force and can be hard to remove. It has entered crop fields and caused problems there, too. NC State reports no major pest or disease concerns. Its weedy growth is the main concern for gardeners. The supplied sources do not show whether it is safe to eat. Nor do they show whether it is toxic.