An erect shrub to about 1.5 metres tall, spreading to about 1 metre wide.
It is endemic to the south-western corner of Western Australia, growing as far north mostly to Badgingarra, extending to Geraldton and east to Wongan Hills, then extending south along the coast and to about 80 km inland, through Perth and south-east to Albany.
It grows on flats along watercourses and swamps and near permanent springs and sometimes on hillsides, on sand, sandstone and peat-soils.
Hypocalymma species have simple and opposite leaves. In this species, leaves are linear and narrow, to about 25 mm long and 1 mm wide, green to grey-green in colour.
Hypocalymma species have bisexual 5-merous flowers with 5 sepals and petals; with up to 80 stamens surrounding 2 or 3 carpels; often produced solitarily or in up to clusters or 4 in leaf axils and at the terminals; white, yellow, pink or red in colour. In this species, flowers can be white or pink (two forms), to about 1 cm in diameter, in low-numbered clusters in leaf axils, appearing in late winter and spring.
The fruit is a dehiscent capsule. In this species, it is about 5 mm across.
Hypocalymma angustifolium is the best known members of the genus and has been widely cultivated over a long time.
I have been growing Hypocalymma angustifolium for many years in my garden in Sydney’s northern suburbs.
I find this species very attractive and was one of the first native plants that I planted many, many years ago as it was then and still is readily available from nurseries.
This plant is suitable for a range of climates and it is easily cultivated in humid, east-coastal areas where other species from the south west are often difficult to maintain. This makes it an ideal small plant for any garden as it only grows to 1.5 metres high and in late winter and spring the small flowers appear. The flowers cover the whole plant to create a very attractive appearance. As well, it is an ideal species for use as cut flowers. The plant requires well drained conditions, in full sun or dappled shade and it is tolerant of at least moderate frost.
In my garden I grow this species in raised beds over my clay sub soil as this gives me good drainage.
The pink flowering form is the most common form available from nurseries and the one I prefer. However there is also a white form available. As the plant is spectacular in flower and a bit inconspicuous the rest of the year, you should purchase the plant in flower, to ensure you are getting the flower colour you prefer.
Pruning and Fertilising: Pruning back by 1/3 to half after flowering will help maintain a dense, bushy growth habit. After pruning, I apply a low-phosphorous fertiliser and give the plant a good watering to promote new growth. I only give additional watering in very dry periods.
Best propagated from cuttings.
Hypocalymma is a small genus of about 29 species, all of which occur naturally only in south Western Australia. There are no species in NSW.
Most Hypocalymma species will regenerate from seed after fire.
Hypocalymma – From Greek hypo (υπό) meaning “under” and calymma (κάλυμμα) – meaning “a veil”, referring to the appearance of the calyx on some species.
angustifolium – From Latin angustus meaning “narrow” and –folius, “a leaf” – referring to the narrow leaves of the species.
This species is not considered to be at risk of extinction in the wild.
Western Australian Herbarium. Florabase: The Western Australian Flora – Hypocalymma angustifolia profile page https://florabase.dbca.wa.gov.au/browse/profile/5817
Gardening with Angus – Hypocalymma angustifolia https://www.gardeningwithangus.com.au/hypocalymma-angustifolium-pink-flowered-myrtle/
Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.