Oblongleaf Bellflower Plant Care

Oblongleaf Bellflower (Clermontia oblongifolia) belongs to the Campanulaceae family within the Clermontia genus. Oblongleaf Bellflower is native to three of the Hawaiian Islands.

Oblongleaf Bellflower displays a tall, upright shrub growth habit, reaching up to 5 ft tall with a spread of approximately 3 ft. Oblongleaf Bellflower produces showy, tubular flowers in various colors.

Leaf size: approximately 6 inches.

Water a young or newly planted Oblongleaf Bellflower every 7–10 days, soaking the whole root zone, until it is established — usually one to two growing seasons. Established trees mainly need water during long dry spells. In a container, water whenever the top few centimetres of soil are dry.

Oblongleaf Bellflower thrives in filtered sunlight. Avoid placing Oblongleaf Bellflower in direct, harsh sunlight for extended periods, as this can scorch the foliage.

Clermontia oblongifolia tolerates temperatures of 60–75°F. Oblongleaf Bellflower prefers humidity levels of 50–70%. A pebble tray or humidifier helps maintain adequate moisture around the plant.

Rich, well-draining soil with high organic matter content. Good drainage is essential for Oblongleaf Bellflower to prevent waterlogging, which leads to root rot and fungal issues.

Feed Oblongleaf Bellflower every 6 months during the growing season with a balanced, slow-release fertilizer at the rate on the label. Established trees in good soil often need little extra feeding, so let weak growth or pale foliage guide you.

Stop feeding by late summer so new growth can harden before winter.

The PlantoScan app can remind you when to water and when to fertilize each plant.

Choose a spot with filtered sunlight and rich, well-draining soil with high organic matter content. Avoid low spots where water collects after rain.

Oblongleaf Bellflower is suited to USDA Zone 13a.

Plant container-grown or balled-and-burlapped trees in spring or early autumn, setting the root flare at soil level, and water well after planting.

Oblongleaf Bellflower can spread to about 3 ft (0.9 m) and reach about 5 ft (2 m) tall. Space plants about 3 ft (0.9 m) apart so mature crowns don't crowd each other, and plant at least half that distance from buildings, fences and paths.

Planning a row or hedge? Try the tree spacing calculator.

Prune Oblongleaf Bellflower while it is dormant in late winter: first remove dead, damaged and crossing branches, then thin lightly for shape.

If it flowers in spring, prune right after flowering instead so you don't remove next year's buds. Never take off more than about a quarter of the tree in one year.

Oblongleaf Bellflower is frost-tender (hardy to USDA zone 13). In colder areas grow it in a container and move it to a bright, frost-free place before the first frost.

Oblongleaf Bellflower can be propagated through seeds, stem cuttings. Similar propagation techniques also apply to kīhāpai plant care, which shares the same genus.

See all plants toxic to cats and plants toxic to dogs.

Oblongleaf Bellflower is susceptible to aphids, spider mites, scale insects. Inspect the foliage regularly, especially along leaf undersides and stems. Treat infestations promptly with insecticidal soap or neem oil to prevent spread.

Yellow leaves, brown tips or drooping? See common plant problems and how to fix them.

Oblongleaf Bellflower grows outdoors in USDA Zone 13a. It survives winters down to planting zone 13a. Oblongleaf Bellflower is native to three of the Hawaiian Islands. In cooler regions, grow Oblongleaf Bellflower as a houseplant or bring it indoors before the first frost.