Square-stemmed St John's Wort Plant Care

Square-stemmed St John's Wort (Hypericum tetrapterum) belongs to the Hypericaceae family within the Hypericum genus. Square-stemmed St John's Wort is also known as Tetrapterum St John's Wort.

Square-stemmed St John's Wort displays an upright, bushy shrub growth habit, reaching up to 3 ft tall with a spread of approximately 2 ft. Square-stemmed St John's Wort produces bright yellow, star-shaped flowers with prominent stamens.

Leaf size: approximately 4 inches.

Water a young or newly planted Square-stemmed St John's Wort 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.

Square-stemmed St John's Wort thrives in full sun to partial shade.

Hypericum tetrapterum tolerates temperatures of 50–80°F. Square-stemmed St John's Wort prefers humidity levels of 40–70%.

Well-draining loamy soil with added organic matter for moisture retention. Good drainage is essential for Square-stemmed St John's Wort to prevent waterlogging, which leads to root rot and fungal issues.

Feed Square-stemmed St John's Wort 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 full sun to partial shade and well-draining loamy soil with added organic matter for moisture retention. Avoid low spots where water collects after rain.

Square-stemmed St John's Wort is suited to USDA Zone 12a.

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.

Square-stemmed St John's Wort 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 Square-stemmed St John's Wort 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.

Square-stemmed St John's Wort is frost-tender (hardy to USDA zone 12). In colder areas grow it in a container and move it to a bright, frost-free place before the first frost.

Square-stemmed St John's Wort can be propagated through softwood cuttings, seeds. Similar propagation techniques also apply to addington's st. john's wort plant care, which shares the same genus.

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

Square-stemmed St John's Wort is susceptible to aphids, 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.

Square-stemmed St John's Wort grows outdoors in USDA Zone 12a. It survives winters down to planting zone 12a. In cooler regions, grow Square-stemmed St John's Wort as a houseplant or bring it indoors before the first frost.