Hoya Australis

How to care for Hoya Australis

Light

Hoya australis thrives in bright, indirect light. A position near an east- or west-facing window is ideal, giving the plant several hours of gentle sun without the intensity of direct midday rays. A south-facing window filtered through a sheer curtain also works well. Insufficient light results in sparse growth and reluctance to flower, while harsh direct afternoon sun can scorch the waxy leaves.

Watering

Water thoroughly when the top half of the compost has dried out, then allow excess water to drain freely. In spring and summer this may mean watering every 7 to 10 days, while in autumn and winter the interval should be extended considerably, sometimes to three weeks or more. Overwatering is the most common cause of decline; Hoya australis stores water in its succulent leaves and is far more tolerant of drought than of waterlogged roots.

Soil and potting

A well-aerated, free-draining mix is essential. A blend of peat-free compost with perlite or pumice (roughly 50:50) suits this plant well, or a commercial orchid bark mixed with standard potting compost. The goal is a medium that retains a little moisture but dries out relatively quickly and never becomes compacted or sodden. Good aeration around the roots reduces the risk of rot.

Feeding

Feed with a balanced liquid fertiliser diluted to half strength once a month during the active growing season of spring and summer. A fertiliser with a slightly higher phosphorus and potassium content can encourage flowering. Do not feed in autumn and winter when growth slows. Avoid over-feeding, as excess nitrogen promotes lush foliage at the expense of blooms.

Humidity and temperature

Hoya australis prefers temperatures between 15°C and 30°C and will not tolerate frost. It is more tolerant of average household humidity than many tropical hoyas but does best at 50% relative humidity or above. In centrally heated homes, grouping plants together, standing pots on a tray of damp pebbles, or using a room humidifier all help. Avoid placing the plant near cold draughts, air-conditioning vents, or radiators.

Repotting

Repot every two to three years in spring, or when roots visibly emerge from the drainage holes. Choose a pot only one size larger, as Hoya australis tends to bloom more freely when slightly pot-bound. Terracotta pots are beneficial as they allow the compost to dry more evenly. Handle the roots gently and use fresh well-draining compost. After repotting, wait a week before watering to allow any disturbed roots to settle.

Pruning

Pruning is not strictly necessary but can be used to manage the plant's size and shape. Remove any dead or damaged stems at the base. Avoid cutting the short, spur-like peduncles (flower stalks) from which blooms emerge repeatedly year after year; removing these reduces future flowering. If the plant becomes excessively long and leggy, stems can be trimmed back in spring. Cuttings removed during pruning can be used for propagation.

Is Hoya Australis toxic?

Common problems

How to propagate

Stem tip cuttings

Take a cutting of 10 to 15 cm with two to three leaf nodes, remove the lowest pair of leaves, and allow the cut end to callous for a few hours. Insert into a mix of perlite and peat-free compost, keep warm and humid, and roots should form within four to six weeks.

Layering

Select a long, healthy stem and wound a node lightly before wrapping it in damp sphagnum moss secured with cling film. Once roots are visible through the moss after several weeks, sever the stem below the rooted section and pot it up.

Where Hoya Australis comes from

Native to Eastern and northern Australia (Queensland, New South Wales, Western Australia, Northern Territory), New Guinea, Solomon Islands, Vanuatu, Fiji.

Story and origins

The genus name Hoya honours Thomas Hoy (c.1750 to c.1822), head gardener to the Duke of Northumberland at Syon House, Middlesex, who was an accomplished botanist and cultivator of exotic plants. The species epithet australis is derived from the Latin word for southern (australis, meaning 'of the south' or 'southern'), referring to the plant's origin in Australia and the southern Pacific region. The name was formally applied by Robert Brown, the Scottish botanist who accompanied Matthew Flinders on his circumnavigation of Australia, and published in his monumental work Prodromus Florae Novae Hollandiae et Insulae Van Diemen in 1810.

Hoya australis was first collected by botanists travelling with Captain James Cook during his voyages to the Pacific in the late 18th century, making it one of the earliest hoyas to come to the attention of European science. It was formally described and named by Robert Brown in 1810. As the hoya genus grew in popularity as an ornamental plant group throughout the 19th and 20th centuries, Hoya australis became a mainstay of collections due to its comparative ease of cultivation and reliable flowering. In its native Australia, it has no particular recorded cultural or medicinal significance among indigenous communities, though it is a well-known component of coastal and dry forest vegetation in eastern Australia.

Varieties to know

Hoya australis subsp. australis

The most commonly cultivated subspecies, bearing classic glossy green leaves and white flowers with red-pink centres.

Hoya australis subsp. rupicola

A subspecies with slightly smaller, rounder leaves native to rocky habitats in Queensland; less commonly available in cultivation.

Hoya australis subsp. tenuipes

Features thinner stems and leaves than the typical form and is native to northern Queensland and New Guinea.

Hoya australis 'Lisa'

A variegated cultivar with green leaves splashed with creamy yellow and occasional pink tones towards the centre; slower growing than the species.

Fun facts

• The flower clusters (umbels) of Hoya australis can contain up to 40 individual florets, each one producing a droplet of nectar that glistens on the petals.
• Each peduncle (flower spur) is capable of producing flowers for many years; once a peduncle has flowered, new flower buds emerge from the same point the following season, so cutting them is a significant loss to the plant's future blooming potential.
• Hoya australis was one of the first hoya species to be collected by European botanists, gathered during Captain James Cook's first voyage to the Pacific in the late 18th century.
• The waxy coating on the leaves is an adaptation to reduce water loss in its native habitat, which can include exposed coastal cliffs and dry sclerophyll forest.
• In the wild, Hoya australis is pollinated by moths and other night-flying insects, attracted by its strong, sweet fragrance that intensifies considerably after dark.

Hoya Australis FAQ