Hakea


Hakea is a genus of about 150 species of flowering plants in the family Proteaceae, endemic to Australia. They are shrubs or small trees with leaves that are sometimes flat, otherwise circular in cross section in which case they are sometimes divided. The flowers are usually arranged in groups in leaf axils and resemble those of other genera, especially Grevillea. Hakeas have woody fruit which distinguishes them from grevilleas which have non-woody fruit which release the seeds as they mature. Hakeas are found in every state of Australia with the highest species diversity being found in the south west of Western Australia.

Description

Plants in the genus Hakea are shrubs or small trees. Some species have flat leaves, whilst others have leaves which are needle-like, in which case they are sometimes divided and sometimes have a groove on the lower surface. The flowers are arranged in groups in leaf axils and are surrounded by bracts when in bud. The flowers have both male and female parts and are borne on a short stalk called a pedicel. The sepals and petals, jointly called tepals, form a curved tube which sometimes splits open as the flower develops. The style is longer than the tepal tube and is curved before its tip is released. When released, the tip of the style is a pollen-presenter. The fruit of hakeas is woody and persists on the plant until burned in a bushfire or until the plant dies. The fruit then splits open to release two winged seeds.
Hakeas are similar to other plants in the Family Proteaceae, but have undivided leaves arranged alternately, sessile flowers arranged in loose groups in the axils of leaves or bracts, unlike those in the Banksia. Hakeas are similar to species of Grevillea but are distinguished from them in having persistent, woody fruits., and the ovary and style are glabrous.

Taxonomy and naming

The genus Hakea was first formally described in 1797 by Heinrich Schrader and Johann Christoph Wendland and the description was published in Sertum Hannoveranum. The genus is named after Baron Christian Ludwig von Hake, an 18th-century German patron of botany.

Distribution

Hakea are endemic to Australia, where they can be found in all six states. Some species, such as Hakea sericea, have been introduced elsewhere, where they have become naturalized and may be considered invasive. Introduced Hakea populations occur in New Zealand, Norfolk Island, South Africa and Portugal.

Horticulture

Hakeas are popular ornamental plants in gardens in Australia, and in many locations are as common as grevilleas and banksias. Several hybrids and cultivars have been developed, including Hakea 'Burrendong Beauty'. They are best grown in beds of light soil which are watered but still well drained.
Some showy western species, such as Hakea multilineata, H. francisiana and H. bucculenta, require grafting onto hardy stock such as Hakea salicifolia for growing in more humid climates, as they are sensitive to dieback.
Many species, particularly eastern Australian species, are notable for their hardiness, to the point they have become weedy. Hakea gibbosa, H. sericea, and H. drupacea have been weeds in South Africa, Hakea laurina has become naturalized in the eastern states of Australia and is considered an environmental weed, and H. salicifolia, H. gibbosa, and H. sericea are invasive weeds in New Zealand.

List of species

The following is a list of Hakea species recognised by the Australian Plant Census, except for Hakea asperma which is recognised by the Royal Botanic Gardens Victoria:Hakea actites W.R.Barker – mulloway needlebush, wallum hakeaHakea aculeata A.S.George – column hakeaHakea acuminata HaegiHakea adnata R.Br.Hakea aenigma W.R.Barker & Haegi – enigma hakeaHakea ambigua Meisn.Hakea amplexicaulis R.Br. – prickly hakeaHakea anadenia HaegiHakea arborescens R.Br. – common hakea, yellow hakeaHakea archaeoides W.R.Barker