Callianthe megapotamica aka Trailing Abutilon

Callianthe megapotamica is a shrub in the mallow family. Gardeners also know it as trailing abutilon or Brazilian bellflower. Older sources call it Abutilon megapotamicum. It comes from southern Brazil, including Rio Grande do Sul. People have introduced it to Bolivia and Madeira. It grows in a subtropical climate. Some sources say no truly wild plants are known. Gardens grow it for its long season of flowers.

This fast-growing shrub has thin, woody stems and arching branches. Some forms spread low across the ground; others grow upright. Garden plants reach about 5–8 feet [1.5–2.5 metres] tall and wide. Some accounts give a height near 6.6 feet [2 metres]. The plant may shed its leaves or keep some year-round. Its green leaves grow one at a time along the stems. Each simple leaf has a long, roughly triangular outline. The base forms a heart shape, with a narrow tip. Fine hairs cover the leaves, and teeth line their edges.

Single flowers hang below the branches like small bells. Yellow petals emerge beneath a large red calyx. Each flower spans about 0.17 feet [0.05 metres]. The blooms have a soft, hairy surface. Each has both male and female parts. Flowers open from summer until frost in temperate gardens. Tropical accounts report that flowering can last all year. Bees, butterflies, and hummingbirds visit the blooms. People eat the sweet flowers raw or cook them as vegetables. PFAF and Useful Tropical Plants list no known hazards. This does not establish safety for pets.

Grow it in a sheltered site with fertile, well-drained soil. Sources support sun or shade for part of the day. Indoors, NC State recommends bright light without direct sun. Keep the soil moist; the plant dislikes drought. It suits loam or sand with added organic matter. Acid or neutral soil is suitable. RHS gives it a UK hardiness rating of H3. NC State lists USDA zones 8b–11b. In colder areas, grow it indoors or under glass. It can also spend summer outside in a sheltered spot.

Use it in beds, borders, pots, or hanging baskets. Its arching growth can also cover an arch. Prune in late winter or early spring to shape growth. Pinching young shoots helps build a bushier plant. Remove faded flowers through the bloom season. Stem cuttings provide a way to raise more plants. Growth can become leggy. Watch for whiteflies, spider mites, mealybugs, and scale insects. Honey fungus and viruses may also cause problems. RHS notes that honey fungus occurs only rarely.