Hakea petiolaris is known as the Sea Urchin Hakea and develops into a tall shrub or small tree, potentially reaching 9 metres tall but often much smaller in cultivation; possessing a lignotuber.
It is another endemic species to the south-west of Western Australia, growing in an area generally surrounding Perth, as far north-west as between Wongan Hills and Koorda, south-east to around Dragon Rocks Nature Reserve (north of Newdegate).
It tends to grow on rocky slopes, on granite and other outcrop, as part of mallee-shrublands and dry sclerophyll woodlands and forest.
Leaves are alternate, large, spathulate (spoon-shaped), to about 9 cm long by 5 cm wide, leathery, blue-green with prominent veins, and with petioles up to 2 cm long.
A hakea inflorescence is technically a cluster of paired flowers, termed a conflorescence (although sometimes the paired flowers are not evident) with the overall structure forming a clustered-raceme-like appearance. The inflorescences are always produced in the leaf axils, as opposed to the closely related Grevillea where they are mostly terminal. They can appear as a spider-flower-like cluster, or a rounded ball where flowers emerge around a 360° radius, or as a cylindrical raceme (which strongly resemble those of Grevillea). In this species, the creamy-purplish-pinkish flowers are held in large globular clusters, about 4 cm across, with up to 200 small flowers in each cluster, carried in the leaf axils and on old wood, from May to July.
Individual flowers are composed of 1 carpel (female part) where the style and stigma protrude out; 4 stamens hidden away in the perianth; and the perianth (petals and sepals collectively) which connects to a pedicel. Proteaceae flowers do not have any discernible petals or sepals (having only one whorl) and so these are referred to as ‘tepals’ of which there are 4. In this species, the perianth is pinkish-purplish, to about 10 mm long, with the carpels cream in colour, to about 20 mm long
The follicles are woody, ovoid, to about 3.5 cm long by 2 cm wide, with a short beak, usually held in attractive clusters.
A species that is known to be cultivated. It is reported to be a hardy and attractive shrub as well as relatively fast-growing. It is a useful screen or feature tree and has very attractive foliage and fruits.
Best planted on a well-drained soil in full sun to a minor amount of shade. Allow some room for its spread.
Three Sea Urchin Hakeas could be grown as an eye-catching specimen copse, as an avenue tree on a rural property or perhaps as a street tree.
Honeyeaters are attracted to the nectar rich blooms.
Propagate Hakea petiolaris from seed.
Hakea is a genus of about 150 species of plants that are endemic to Australia, first described in 1788 by Joseph Gaertner, a German botanist. NSW currently has about 31 species, some which are species-complex.
Hakeas are similar to species of Grevillea but are distinguished from them in having persistent, woody fruits. Those of grevilleas are not persistent and not woody.
The fruit of Hakea spp. generally persist on plants until burned in a bushfire or until the plant dies. The fruit then splits open to release two winged seeds. This species also has a lignotuber from which it can re-sprout after fire along with any seedbank or dispersal.
Hakea – named after Baron Christian Ludwig von Hake (Baron von Hake of Hanover, 1745-1818), an 18th-century German patron of botany (and for whom not a lot of information can be found).
petiolaris – Latin – “petiole-bearing” – referring to the comparitively larger leaf petioles of this species. The type specimen was collected in the York area, east to Perth, Western Australia in the early 1840’s.
This species is not considered to be at risk of extinction in the wild.
Western Australian Herbarium (1998–). Florabase—the Western Australian Flora – Hakea petiolaris profile page https://florabase.dbca.wa.gov.au/browse/profile.php/2194
Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.
Electronic Flora of South Australia – Hakea petiolaris subsp. petiolaris profile page http://www.flora.sa.gov.au/efsa/lucid/Hakea/key/Australian%20Hakea%20species/Media/Html/Hakea_petiolaris_ssp._petiolaris.htm