Publication: Trans. Hort. Soc. London 7: 28 1830
Description
Hoya australis, commonly known as the Waxvine or Common waxflower is a popular plant grown for its attractive glossy foliage, and sweetly scented wax-like white flowers with cerise inner markings under the white corona. It is attractive not only because of its fragrance and waxy appearance but also because of the fact that each flower looks like a five-pointed star and the cluster of flowers also arranges itself in a star shape. Often several flower-clusters open at the same time and the fragrance can be overpowering. There are many different subspecies of Hoya australis, but the flowers are almost always the same. The long, narrow fruit contains many feathery seeds that float in the wind.
Habit: It is an evergreen, climbing vine which may reach 4–10 metres.
Stems Tining, terete, succulent, somewhat woody when old, glabrous or hairy when young.
Leaves: 2 cm petiolate, simple opposite, succulent (thick and fleshy) to leathery, narrowly elliptical, ovate or rounded in shape, acute, shortly acuminate or acuminate, base rounded, cordate, obtuse or cuneate, margin weakly revolute, glabrous (shiny), sparsely to densely hairy, 3–15 cm long and 2–12 cm wide. Leaves growing in sunnier positions are a more yellowish-green while those in shadier locales are dark green in colour.
Inflorescences: The flowers appear in pendent axillary umbellate clusters (10-50-flowered) at the apex of 5–30 mm long peduncles, glabrous or hairy. Pedicels 2 - 4 cm long; Sepals ovate to triangular, 1-5 x 1-3 mm, sparsely to densely hairy.
Flowers: Corolla 1–2.5 cm in diameter, cup-shaped, with five thick, waxy, petal-like lobes, and white to cream-coloured with each lobe marked red. Corolla-lobes triangular-ovate, 5-10 x 3-7 mm, acute, margin revolute. Corolla-lobes ovate, 5-10 x 3-7 mm. acute, margin revolute; Corona cream-coloured; Corona-lobes lobes ovate, 1.2-3.5 x 1-2.5 mm, upper face concave, lower face channelled, outer appendage rounded, inner appendage acute. Style head conical. Pollinia elongate, approx. 0.7 x 0.3 mm, corpuscle ovate-oblong, 0.35 x 0.2 mm, caudicles winged. They have a strong sweet scent and produce abundant nectar.
Blooming season: Flowering may occur at any time of year. The flowers last about one week.
Fruits: Spindle-shaped 9-13 cm long 1-1.5 cm in diameter
Seeds. Elongate, 5-7 x 2-3 mm, tan-coloured, tuft of hairs 2.5- 3 cm long.
Origin and Habitat
Indonesia, Australia (Eastern and northern Australia, from the Northern Territory though coastal Queensland from Cape York to northern New South Wales), Fiji, New Caledonia, Papua New Guinea, Solomon Islands, Samoa, Tonga, Vanuatu.
Habitat: It is a vine found on rainforest margins and rocky areas especially in coastal areas. It is a popular garden plant, widely cultivated in the tropics for its fragrant flowers.
Ecology: It serves as a food plant for the caterpillars of the Queensland butterfly the No-brand Crow (Euploea alcathoe), and the Common Australian Crow. Flowers are pollinated by the Southern Grass-dart (Ocybadistes walkeri).
Cultivation and Propagation
Hoya australis is a popular garden plant in the tropics and also an excellent plant for house culture as it stands the extremes of heat and cold better than most plants, and is not easily injured by neglect. There are a few Hoya’s which make ideal houseplants, Hoya australis is one of them. Keep moist and fed these attractive plants will climb or trail. To climb they will need a supporting frame, and to trail a hanging basket is ideal.
Growth rate: Although the vines can reach lengths of 10 m in the wild, cultivated plants generally extend 1,5-2 m, twisting around supports to which they cling or hanging down in attractive cascades from suspended pots. The all green variety tends to grow more quickly and is arguably more hardy, but it also comes in a some pretty slow growing variegated varieties.
Potting medium: It benefits from being potted up in a very well-draining and porous potting medium that allows some air to get to the roots; typical mixes include, peat, with some fibrous soil and sand along with large-grade drainage material such as perlite, pumice, or ceramic balls. Often specialized hoya growers either use only chopped coconut husk or a good orchid potting mixture for growing their hoya plants. The medium needs to be moisture-retentive.
Fertilization: The plants should be fed regularly with a fertilizer suitable for epiphytic plants.
Watering: With its succulent qualities it’s quite adapt at storing water for longish periods of time between waterings. Water regularly in summer, but do not overwater ( wet-sensitively) and let the plants to dry out between watering and then water again. Its roots are easily lost in pots that stay damp for any length of time. Keep quite dry with ample airflow in winter (It would probably tolerate one watering a month). In the rest period no high atmospheric humidity. Care must be taken with watering as they tends to become swollen and untidy in growth habit if given too much water and shade.
Fertilization: During the growing season enrich the soil using a fertilizer rich in potassium and phosphorous, but poor in nitrogen, because this chemical element doesn’t help the development of succulent plants, making them too soft and full of water.
Exposition: This hoya species flowers best a well-lit position, but will tolerate much less. Outside half shade to shade (filtered sunlight or afternoon shade tolerated) , inside it will need a reasonably light room in order to actually grow, although it will still get by even in a shadier spot and can be positioned almost anywhere in homes or offices. It subject to sunburn if exposed to direct sun for too long. Tends to bronze in strong light, which encourages flowering and heavy leaves production.
Hardiness: The optimal temperature is 16-30°C (USDA Zones: 10 -12 ).
Spring: When winter ends and they begin to grow again, they will require much water and soaking the pots will no longer put the plants at risk for rot. In the spring they will grow well in partial shade and leaving them out in the rain may provide them with the water they need.
Summer: In the summer months they will tolerate heavy rain, but will be just as happy if the season is dry. They will tolerate hot weather outdoors as long as they are kept in strongly filtered light and this will encourage them to flower. They also enjoy some fertiliser. Moving the plants as they are developing buds may cause them to spontaneously abort the flowers all together.
Autumn: In the fall keep them outdoors until the night time temperatures drop below the 10°C.
Winter: Winter care presents no problems at 10° C with plenty of light. In winter be sure to take extra precautions to keep them dry, because damp cool conditions when the plants are resting is an invitation to fungal infections, but - according to temperatures –some occasional lit watering may be useful.
Garden uses: It is often grown in containers and trained to grow on trellises on verandahs, fences and in glasshouses. It is a butterfly-attracting plant in the garden. It can be grown indoors provided it receives direct sunlight.
Maintenance: Prune the plant lightly to keep it tidy.
Repotting: In any season it’s best to lay the stems out for several days before replanting them and then pot them only in dry soil and withhold any water until they begin to shrivel or start growing again. Re-pot every 2 years.
Traditional uses: It is used for treating wounds and rashes.
Warnings: It is poisonous to stock.
Pest and diseases: Hoya are generally fairly easy to grow, especially if kept pest-free. They are very susceptible to stem and root mealy bugs, and damage from these may well initiate fungal attack. Any time when there is a dead or dying stem in the pot it is important to remove it immediately and completely before other healthy stems can become ill too, isolate the healthy parts, dry them off, and re-root them in new compost.
Propagation: Hoya australis is easily propagated from cuttings. The stems produce aerial roots which roots easily when inserted into a moist medium making it easy to propagate new plants from stem cuttings. Allow cuttings to dry a day before planting. A very good method is to wrap a cutting in moss, keeping it moist until the roots are well started. It can also be increased from seeds sowing in spring in moist, sandy peat moss. Barely cover seeds. Seeds germinate quickly.
Bibliography
Major references and further lectures
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Simpson DP “Cassell’s Latin Dictionary” (5 ed.). London: Cassell Ltd.1979
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Focke Albers, Ulrich Meve “Illustrated Handbook of Succulent Plants: Asclepiadaceae” Volume 4 Springer, 2002
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James Cullen, Sabina G. Knees, H. Suzanne Cubey “The European Garden Flora Flowering Plants: A Manual for the Identification of Plants Cultivated in Europe, Both Out-of-Doors and Under Glass” Cambridge University Press, 11/ago/2011
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Dale Kloppenburg, Ann Wayman “The Hoya Handbook: A Guide for the Grower and Collection” Orca Publishing Company, 1992
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Anders Wennström und Katarina Stenman “The Genus Hoya - Species and Cultivation”, Botanova, Umeå 2008
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Elliot, Rodger W.; Jones, David L.; Blake, Trevor. “Encyclopaedia of Australian Plants Suitable for Cultivation” Vol. 5. Port Melbourne: Lothian Press. 1990
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Braby, Michael F. “The Complete Field Guide to Butterflies of Australia.” Collingwood, Victoria: CSIRO Publishing. 2005
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Clyne, Densey “Attracting Butterflies to Your Garden.” Sydney: Reed New Holland. 2000
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Forster, Paul I. “Pollination of Hoya australis (Asclepiadaceae) by Ocybadistes walkeri sothis (Lepidoptera: Hesperidae)”. Australian Entomological Magazine 19: 39–43.1992
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Ratcliffe, David & Patricia “Australian Native Plants for Indoors.” Crows Nest, NSW: Little Hills Press. 1987
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Umberto Quattrocchi “CRC World Dictionary of Medicinal and Poisonous Plants: Common Names, Scientific Names, Eponyms, Synonyms, and Etymology” (5 Volume Set) CRC Press, 03/mag/2012
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RC Cambie, J Ash “Fijian Medicinal Plants ”Csiro Publishing, 01/gen/1994