Water starwort Plant Care

Water starwort (Trithuria submersa) belongs to the Hydatellaceae family within the Trithuria genus. Water starwort is native to the Australian states New South Wales, South Australia, Tasmania, Victoria, and Western Australia. Water starwort is also known as Submerged trithuria.

Water starwort displays a low rosette, spreading growth habit, reaching up to 0.5 ft tall with a spread of approximately 1 ft. Water starwort produces tiny inconspicuous flowers.

Leaf size: approximately 1 inches.

Water a young or newly planted Water starwort every 3–5 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.

Water starwort thrives in full sun to partial shade.

Trithuria submersa tolerates temperatures of 60–80°F. Water starwort prefers humidity levels of 50–70%. A pebble tray or humidifier helps maintain adequate moisture around the plant.

Sandy, loamy soil with good drainage. Good drainage is essential for Water starwort to prevent waterlogging, which leads to root rot and fungal issues.

Feed Water starwort 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 sandy, loamy soil with good drainage. Avoid low spots where water collects after rain.

Water starwort is suited to USDA Zone 8b – 10b.

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.

Water starwort can spread to about 1 ft (0.3 m) and reach about 1 ft (0 m) tall. Space plants about 1 ft (0.3 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 Water starwort 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.

Water starwort is hardy down to USDA zone 8b, so once established it can stay outdoors through winter in that zone and warmer ones.

Water deeply in late autumn before the ground freezes, and spread a 5–8 cm (2–3 in) layer of mulch over the root zone, keeping it away from the trunk.

Young and container-grown shrubs need extra protection: roots in a pot freeze much more easily than roots in the ground.

Water starwort can be propagated through division, seeds. Similar propagation techniques also apply to slender mudmat plant care, which shares the same genus.

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Water starwort is susceptible to aphids, 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.

Water starwort grows outdoors in USDA Zone 8b – 10b. It survives winters down to planting zone 8b. Water starwort is native to the Australian states New South Wales, South Australia, Tasmania, Victoria, and Western Australia.