Geography and distribution
Confined to the lower coastal slopes of the Mount Arid granitic massif, which projects into the Southern Ocean as a prominent peninsula east of Esperance, southwest Western Australia.
Eucalyptus sweedmaniana on Mt Arid (Photo: Luke Sweedman)
Eucalyptus sweedmaniana is a sprawling to prostrate mallee (shrub) up to 1 m high and 5 m wide. The root crown has a starchy swelling known as a lignotuber, and this allows the plant to survive fire and to re-sprout when conditions are favourable again. The bark is silver-grey, smooth and shiny when fresh.
Mature leaves are green, glossy, broad-lanceolate, robust and angular and average 20 cm in length and 5.3 cm in width, with prominent venation and scattered intersectional oil glands.
The inflorescences are axillary and unbranched, comprising shortly-winged and down-curved flowering stems bearing single flowers. Flower stalks are absent. The buds are red, pendulous and square in cross section, cuboid to shortly oblong, tapering towards the base, very slightly ribbed and very prominently winged. The stamens are 8 to 10 mm long and pink with a broadly pyramidal, red operculum (a cap that protects the stamens in the bud). Staminodes (sterile stamens) are present.
The fruits average 3.6 cm long and 3.4 cm wide, are square in cross-section, cuboid to shortly oblong and very prominently winged. There are four enclosed valves. Seeds are dark grey, 4 to 5 mm x 3 to 4 mm x 1.5 mm, and flanged.
Threats and conservation
The single known population of Eucalyptus sweedmaniana is in Cape Arid National Park and is therefore not currently under threat from loss of habitat. However, inappropriate fire management regimes involving frequent autumn burns may threaten survival of the population. Some mallees in New South Wales successfully re-sprout after summer fires but have shown up to 90% mortality after annual autumn burns.
Millennium Seed Bank: Seed storage
Kew's Millennium Seed Bank Partnership aims to save plant life world wide, focusing on plants under threat and those of most use in the future. Seeds are dried, packaged and stored at a sub-zero temperature in our seed bank vault.
Description of seeds: Dark grey, 4-5 mm x 3-4 mm x 1.5 mm, flanged.
Number of seed collections stored in the Millennium Seed Bank: One collection of 963 seeds from Mount Arid, Western Australia.
Eucalyptus sweedmaniana is established in Kings Park and Botanic Garden, Perth, Western Australia as an ornamental. Once seeds are available from these recently planted stocks, the species will be available more widely for horticultural use.
Sweedman's mallee at Kew
An isotype (preserved reference specimen) is located in Kew’s Herbarium (one of the behind-the-scenes areas of Kew), where it is made available to researchers by appointment.
The discovery of Sweedman's mallee
Eucalyptus sweedmaniana was discovered in 2006 on the burnt coastal slopes of the Mount Arid granite inselberg in SW Australia. The then-Director of Kew, Professor Stephen Hopper, and Luke Sweedman, the Curator of the Western Australian Seed Technology Centre in Kings Park and Botanic Garden, Perth, were exploring this remote area in search of previously unrecorded species of flowering plants, especially those that appear briefly only after summer wildfire.
The new eucalypt is sister to the widely planted ornamental four-winged mallee (Eucalyptus tetraptera), sharing with it large often red-pink flowers and fruits, and large long-lived leaves.
Professor Hopper and colleagues have named more than 100 new eucalypts from the Southwest Australian Floristic Region over the past three decades, ranging from tall forest trees to knee-high shrubs like E. sweedmaniana.