Hakea - Background

Introduction

Hakea is a member of the Protea family (Proteaceae) and its close relatives include Banksia, Grevillea, Isopogon and Telopea (the Waratah). Hakea is named after Baron Christian Ludwig von Hake a German patron of botany. There are about 130 named species in the genus with a number of others which are yet to be formally described. All species of Hakea are endemic to Australia. Hakeas can be found in many different environments; the tropics, mountains, the coast and desert areas. The most diversity in the genus occurs in the south of Western Australia.

Although there are many ornamental and colourful species in the genus, Hakea has not achieved the same popularity in cultivation as its relatives Grevillea and Banksia. In some ways Hakea forms a link between those two genera having hard woody seed pods with Banksia-like seeds while the flowers occur in Grevillea-like clusters.

Characteristics

   Hakea bakeriana
   Hakea bakeriana - showing the typical flowers and seed pods of the genus. Photo: Brian Walters

The flowers of Hakea species are quite small but they occur in clusters (an inflorescence) which, in some species, may consist of perhaps 100 or more individuals. The sequence of opening of each flower is similar to other members of the Proteaceae and goes through several stages:

  1. In bud, each flower appears as an elongated narrow tube (the perianth) comprising four segments each having an anther containing pollen at its tip.
  2. As the flower opens, the perianth segments separate to reveal a narrow style. Just before the flower fully opens the anthers transfer their pollen to the tip of the style (the stigma)
  3. Finally, the style separates from the perianth. At this stage the style and stigma, with attached pollen, is called a 'pollen presenter' (i.e. it is 'presenting' the pollen to a pollinator, usually a bird or small marsupial, which acts as the agent to transfer pollen from one flower to another for fertilisation.

This sequence is shown in the accompanying diagram (which is based on the opening of a Banksia flower).

Banksia flower opening   
Stages of opening of a Banksia flower (Hakea is similar)   

The inflorescences can be quite variable in arrangement but two that are commonly recognised are the "spider" flower arrangement, in which the flower styles arise from a rounded inflorescence like the legs of a spider (as in many grevilleas), and the "pincushion" shape where the flowers occur in a globular-shaped cluster. Another arrangement is an elongated "brush" shape where the flowers are clustered into cylindrical racemes usually at the ends of branches where they are very conspicuous.

Many (but by no means all) hakeas have stiff leaves with sharp points. This feature has probably contributed to the relatively slow uptake of the genus in general horticulture but it does make hakeas excellent plants for boundaries or places where it is desired to restrict access. It also makes them ideal plants to offer protection to birds from predators such as cats.

Hakeas generally flower in winter and spring. The flowers are followed by hard, woody seed pods each containing two seeds and, in the majority of species, these pods remain tightly closed unless stimulated to open by heat, such as following a bushfire, or by the death of the plant. The seeds themselves have a papery wing which allows them to be distributed by wind. Those species native to areas where fires occur at regular intervals often have a "lignotuber", a woody swelling at or below ground level from which regeneration of the plant can occur if the above ground stems are destroyed.

Most hakeas are small to medium shrubs but some can reach small tree proportions. There are no truely prostrate species despite the existance of a species called H.prostrata (this may be prostrate in some forms but is commonly a small tree!). Unlike its relative Grevillea, chance hybridisation in Hakea is virtually unknown and there are few named cultivars. There is little or no deliberate breeding being undertaken with the genus.

One of the great features of hakeas in gardens is that many attract honey-eating birds which act as pollinators for the plants. A number of species rely on other methods of pollination, eg, beetles, moths, bees, ants, and even small marsupials.


◄◄ Hakea Index    Top ▲