Smooth Phialanthus Plant Care

Smooth Phialanthus (Phialanthus glaberrimus) belongs to the Rubiaceae family within the Phialanthus genus. Smooth Phialanthus is native to Brazil, Bolivia, Peru. Smooth Phialanthus is also known as Smooth Rockwort.

Smooth Phialanthus displays a compact, spreading shrub growth habit, reaching up to 2.5 ft tall with a spread of approximately 3 ft. Smooth Phialanthus produces small white fragrant flowers in clusters.

Leaf size: approximately 4 inches.

Water a young or newly planted Smooth Phialanthus 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.

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

Phialanthus glaberrimus tolerates temperatures of 65–80°F. Smooth Phialanthus prefers humidity levels of 50–70%. A pebble tray or humidifier helps maintain adequate moisture around the plant.

Well-draining, acidic soil mix with peat moss and perlite. Good drainage is essential for Smooth Phialanthus to prevent waterlogging, which leads to root rot and fungal issues.

Feed Smooth Phialanthus 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 peat moss and perlite. Avoid low spots where water collects after rain.

Smooth Phialanthus is suited to USDA Zone 13b.

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.

Smooth Phialanthus can spread to about 3 ft (0.9 m) and reach about 3 ft (1 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 plant spacing calculator.

Prune Smooth Phialanthus 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.

Smooth Phialanthus 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.

Smooth Phialanthus can be propagated through stem cuttings, air layering. Similar propagation techniques also apply to none known plant care, which shares the same genus.

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

Smooth Phialanthus is susceptible to mealybugs, scale insects, spider mites. 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.

Smooth Phialanthus grows outdoors in USDA Zone 13b. It survives winters down to planting zone 13b. Smooth Phialanthus is native to Brazil, Bolivia, Peru. In cooler regions, grow Smooth Phialanthus as a houseplant or bring it indoors before the first frost.