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The genus Hypocalymma

Colin Cornford

Hypocalymma is part of the Myrtaceae family of plants in the Chamelaucium Alliance, which also includes Astartea, Calytrix, Homalocalyx, Thryptomene, Micromyrtus etc. There are 23 named species in the genus (plus some unnamed species), all of which are endemic to south-west Western Australia. All species in the genus are small woody shrubs which produce a profusion of flowers in the leaf axils on erect stems, with colours ranging from white to pink (light and dark shades) to yellow. Their natural habitat varies from wet, swampy country (H.cordifolium) to well-drained situations but, in cultivation, it seems all species must have good drainage to survive. H.robustum and H.augustifolium were introduced into cultivation in England in 1843 under the names of Swan River Myrtle and White Myrtle as the flowers resemble those of the European Myrtles.

Brief details of some of the species in the genus are:

Hypocalymma robustum - grows to about 1.5 metres with an erect habit and small, narrow leaves. Flowers are bright pink, clustered in the leaf axils, and seen from mid-winter to late-spring . It is often used as a cut flower . This plant grows naturally in open forest so will tolerate some light shade.

Hypocalymma augustifolium - grows to about 2 metres with narrow, aromatic foliage. Profuse axillary flowers on long arching branches are seen from mid-winter to early summer. In general, flowers open white and age to pink but pure white and cream forms are sometimes found. This plant benefits from quite severe pruning after flowering. Full sun or light shade is preferred for optimum growth.

The Genus Hypocalymma
Hypocalymma augustifolium
Hypocalymma cordifolium
Hypocalymma robustum
Hypocalymma speciosum
Hypocalymma xanthopetalum
Photos: Tony Cavanagh, Chris Clarke, Brian Walters, Geoff Warn.

Hypocalymma strictum is generally less than 1 metre in height with needle-like leaves and an upright habit. Scented, pink flowers are seen from early summer to mid-autumn. This plant prefers sandy soils with some shade and is fairly resistant to drought conditions.

Hypocalymma xanthopetalum is, generally, a rounded shrub to a height of some 2 metres and although it Ikes full sun, it will tolerate some shade. Leaves of this plant are hairy. Bright yellow flowers are seen from mid-winter to mid-spring.

Hypocalymma speciosum produces single, deep pink flowers in the leaf axils in spring. It may be either a dense or spreading shrub to a height of 0.7 metres. Leaves are quite large being almost round and up to 8 mm long. It requires very good drainage and prefers semi shade.

Hypocalymma cordifolium is a rounded shrub to a height of 1 metre with heart-shaped leaves to a length of 10 mm. Young leaves and stems tend to be reddish. Fairly insignificant white flowers are seen in spring. This species grows naturally in wet situations in Jarrah forests and is an excellent foliage plant.

From the newsletter of ASGAP's Melaleuca and Allied Genera Study Group, June 2002. Sadly, Colin Cornford passed away in June 2007.

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Australian Plants online - 2007
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