Hakeas
Pauline Wicksteed
Hakea is one of the major groups in the Proteaceae family and were named for Baron von Hake, a German patron of botany. There are about 150 species, most in Western Australia, with around 40 species in the eastern states. The recent revision of the genus by W and R Barker and Laurie Haegi of the South Australian Herbarium has provided names for some previously unnamed species and change of names for others. Several species were cultivated in England in the 1790s - Hakea dactyloides, H.sericea, H.gibbosa, H.salicifolia for example.
Characteristics
Hakeas range from small trees to small shrubs, mostly medium shrubs, with smooth bark , apart from the corkwoods, either upright or multi-stemmed. While their flowers appear similar to those of Grevillea. the plants are distinctive by their fruits which are woody and persistent whereas those of Grevillea are non-woody and non-persistent, except for Grevillea glauca. Usually fruits remain on the plant until fire or damage causes them to split open and release the seeds though a few species shed their seed when it is ripe. Apart from their fruits, plant differences occur in leaves - where Hakea leaf surfaces appear similar, grevilleas differ between upper and lower surfaces and, in the ovary which, in the hakeas (except corkwoods) is sessile, in grevilleas is stipitate. Other characteristics include leaf symmetry, ovary and style.
The genus has been classified by leaf forms under descriptive groups - grass-leaf or multilineata, sulcate, fan-leaved, ulicina or gorse-like, falcate, strumosa, needlewoods, corkwoods, verrucosa, varia, shell-like etc. About half the species have stiff prickly foliage and for some the foliage is the main decorative attribute. Probably the most stunning is H.victoria, the Royal Hakea, best seen in the Barren Ranges of Western Australia's Fitzgerald River National Park.
Inflorescences usually arise in axils of young leaves and are erect though with some, such as corkwoods, they are pendant. In some species flowers are borne on older wood within the plant. H.orthorrhyncha has brilliant red flowers along the branches as does H.obtusa with red/cream flowers and H.bakeriana has flowers in hidden clusters on mature wood. In other species examples occur of cauliflory as in H.petiolaris. Flowers are usually bisexual with flower buds recurved at the apex. The indumentum on pedicel and perianth is of great taxonomic importance, ie. whether they share the same hair covering or lack of it. The ovary in all species is glabrous with a nectar gland at its base. The pollen presenter at the apex of the style is another important diagnostic - in some species it is erect and conical but in most groups it is oblique and discoid. Flowering occurs mainly in late winter/spring and flower colours vary from white, cream, pink, red and blue (H.lehmanniana). Many flower in profusion, some feature ornamental fruit while others are noted for fragrance.
| Photos: Australian Plants Society; Brian Walters |
The fruits are ovoid or obovoid consisting of a woody follicle usually beaked or homed that opens to two valves each with a seed cavity containing a winged seed. The fruit splits down both sides, not just along one side as with other Proteaceae. Retention of seed on the plant gives protection to enable release after fire. Some species can re-sprout from a lignotuber, suckering, or rarely epicormic shoots, otherwise the plants are killed by fire and rely on seeds for regeneration. The winged seeds are then dispersed to fresh sites for germination and seedling growth.
Cultivation
Most hakeas tolerate a wide range of soil and climate conditions. They grow well in sandy and clay loams, preferring a site in full sun or partial shade. Fruits can be put in a warm place such as a sunny window sill where they will open quickly to release the seeds. No pre-sowing treatment is required. The seeds should be placed on a moist seed mix, covered lightly and kept moist. Germination will vary from 15-100 days, depending on species, in mild conditions. Initially seedlings emerge with their dark seed coat attached - most shed it quickly but it may be necessary to intervene gently to prevent misshapen stems. Seedlings should be pricked out early, probably at the cotyledon stage, to prevent damage to the fibrous root system. Good ventilation is essential to avoid damping off. Many species can be successfully propagated by cuttings of young, firm growth, and difficult Western Australian species have been grafted to survive east coast conditions using H.salicifolia as the root stock.
Some hakeas are listed as rare and endangered, and of particular interest recently is the appearance of fruit on nursery plants of Hakea pulvinifera at the Australian National Botanic Garden where propagation efforts have been undertaken over several years. This species is known from a single population beyond Gunnedah in New South Wales. In the wild population, it is believed to have lost the ability to set seed or fruit so this news has created great excitement.
Hakeas deserve to be grown more widely as they have such a range of garden uses and most are ornamental with striking flowers which attract nectar-feeding birds, insects and mammals.
References
CSIRO Publishing/Australian Biological Resources Study (1999); Flora of Australia Volume 17B - Proteaceae 3: Hakea to Dryandra
Holliday, Ivan (2005); Hakeas: a field and garden guide.
From the newsletter of the Australian Native Plants Society (Canberra), September 2006.
Australian Plants online - 2006
Association of Societies for Growing Australian Plants
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