Cyanea undulata Plant Care

Cyanea undulata (Cyanea undulata) belongs to the Campanulaceae family within the Cyanea genus. Cyanea undulata is native to the island of Kauai.

Cyanea undulata displays a tall, upright shrub growth habit, reaching up to 3 ft tall with a spread of approximately 2 ft. Cyanea undulata produces showy, colorful bracts with small flowers.

Leaf size: approximately 8 inches.

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

Cyanea undulata thrives in bright indirect light. Avoid placing Cyanea undulata in direct, harsh sunlight for extended periods, as this can scorch the foliage.

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

Well-draining, acidic soil mix with added organic matter. Good drainage is essential for Cyanea undulata to prevent waterlogging, which leads to root rot and fungal issues.

Feed Cyanea undulata every 6 months during the growing season with a balanced, slow-release fertilizer at the rate on the label. Established shrubs 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 bright indirect light and well-draining, acidic soil mix with added organic matter. Avoid low spots where water collects after rain.

Cyanea undulata is suited to USDA Zone 13a.

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

Cyanea undulata can spread to about 2 ft (0.6 m) and reach about 3 ft (1 m) tall. Space plants about 2 ft (0.6 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 plant spacing calculator.

Prune Cyanea undulata 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 shrub in one year.

Cyanea undulata 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.

Cyanea undulata can be propagated through seeds, division of offsets. Similar propagation techniques also apply to haleakala silversword plant care, which shares the same genus.

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Cyanea undulata 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.

Cyanea undulata grows outdoors in USDA Zone 13a. It survives winters down to planting zone 13a. Cyanea undulata is native to the island of Kauai. In cooler regions, grow Cyanea undulata as a houseplant or bring it indoors before the first frost.