Hoya australis

Origin and history of Hoya australis

Hoya australis was described in 1830. Its range extends from parts of Malesia and New Guinea through northern and eastern Australia to the south-western Pacific. It grows on trees in wet and seasonally dry tropical habitats. The species includes several subspecies, with differences in leaf shape, texture and habit; these include climbers and a scrambling subshrub.

Caring for Hoya australis at home

Provide bright filtered light at about 16–24°C, away from cold draughts. Moderate to high humidity with gentle airflow is useful. Give lengthening stems a support where needed, or allow them to hang. Keep the plant’s position steady while buds develop and retain living flower stalks after flowering.

Use a pot with drainage holes and an airy, peat-free mix with bark and a coarse drainage material. Water when the pot is lighter and the mix inside remains lightly moist, then drain fully. As growth slows, allow it to become fairly dry between waterings, without leaving the root ball completely dry.

Feed lightly with balanced orchid fertiliser, preferably urea-free, about every two weeks while growing, following the label. Pause when growth stops and flush with plain water every few months. Once roots fill the container, repot into one only a few centimetres wider. Check whether the fresh compost contains feed and follow its advice on when to begin fertilising.

When new growth begins, trim weak or crowded shoots lightly above a leaf or side shoot. Wear gloves because the sap can irritate skin, and use a clean blade. Choose a semi-ripe shoot with a firm base and a tip that is still soft. A section with nodes can root in water after its lower leaves are removed. Keep leaves above water and roots submerged; once well rooted, pot into airy mix and keep it lightly moist while establishing.

Common signs that Hoya australis is unhealthy

• Yellowing, wilting or dieback in wet mix: Persistent wetness can damage roots. Drain trapped water and inspect roots if decline continues. If you find a small amount of root rot, use a clean, disinfected tool to cut the soft roots back to firm, healthy tissue. Throw away the rotten roots and old mix. Repot in fresh, airy mix, using a clean pot just large enough for the roots that remain. The pot must have drainage holes. If decay is widespread, save only healthy stem cuttings. Discard the plant if no healthy stems remain, and disinfect your tools afterwards.
• Sudden blackening or leaf drop after cold exposure: Chilling can damage leaves and stems, especially beside cold glass or in a draught. Move the plant to a stable, warmer position. Check the mix before watering; a chilled plant may use water more slowly. Remove only tissue that is clearly dead or decaying.
• Brown tips with a white crust on the pot or mix: Accumulated fertiliser or mineral salts may be involved. Pause feeding and, if the pot drains freely, flush the mix with plenty of plain water and drain fully. Replace heavily encrusted or poorly draining mix. Resume feeding only after growth recovers, within the fertiliser label’s instructions.
• White cottony wax on stems or leaf undersides: Confirm mealybugs beneath the wax and isolate the plant. Remove visible insects with a damp swab or tweezers. Inspect sheltered leaf joints, stems, the pot and any support weekly, removing any mealybugs you find until none remain. If mealybugs persist, use a product approved for home use against mealybugs on indoor ornamental plants in your country. Follow the label for how much to use, where to apply it, when to repeat treatment and all safety precautions.

Hoya australis is non-toxic to people and pets

• This plant is non-toxic to people, cats and dogs.
• Chewing a large amount can still cause an upset stomach.
• If a large amount is eaten and symptoms continue, contact a veterinarian or medical professional.

What does the name Hoya australis mean?

Hoya honours the English gardener Thomas Hoy. The epithet australis is Latin for southern and refers to the species range.

Robert Brown established the genus Hoya in 1810 in Prodromus Florae Novae Hollandiae, page 459.

James Traill first described Hoya australis in 1830 in Transactions of the Horticultural Society of London, volume 7, page 28; Robert Brown had proposed the name.