Family: Proteaceae

There are more than 250 species of these decorative, evergreen Australian plants, the largest genus in the family Proleaceae. They vary greatly in form, habit, leaf shape, flower structure and size, from tall rainforest trees (G. robusta) to prostrate rockery plants (G. lavandulacea). There are grevilleas with clusters of flowers, called the spider flower grevilleas, and those with elongated, spike-like, one-sided flowers, called the toothbrush grevilleas.

Grevillea flowers have no separate petals, the long styles forming a major part of the clusters of flowers. Most grevilleas have brightly coloured flowers, often during spring and summer in the northern hemisphere, and attractive foliage, and make beautiful ornamentals.

Many smaller species can be used as pot plants. The low-growing species are particularly suitable for planting on banks and on tops of walls where their pretty flowers can be seen to full advantage. Other species make excellent cut flowers, and some are already grown commercially.

A good deal of research has been carried out on these plants and there are several major groups of cultivars available, among them the 'Poorinda' and 'Clearview' range. 'these cultivars are now being grown extensively in various countries, especially in warm areas of the United States, South Africa and New Zealand.

Grevilleas are easy to cultivate and ecologically beneficial, as long as soils are well drained. A large number of species are readily available from garden centers throughout the year.

Species

G. acanthifolio occurs nat­urally in the Blue Mountains of New South Wales and is one of the few grevilleas that can tolerate wetter soils and some shade. It varies in form from an upright shrub of about 3 m (10 ft) to a low, spreading one. It has stiff, deeply divided leaves, with sharply pointed lobes, and mauve to pink flowers of the toothbrush type.

G. alpina varies a good deal in form, leaf shape and flower colour and can tolerate very cold con­ditions. It generally has small, grayish green leaves and either red, yellow, pink or white flowers.

G. banksii, a popular species from Queensland, named after Sir Joseph Banks, is an erect grower with large heads of red flowers throughout most of the year and deeply lobed, dark green leaves. It grows to 2-8 m (6-26 ft) tall. There is also a white-flowered form.

G. biternata (Synonym: G. curviloba) generally takes a prostrate form. It has become a popular groundcover. It has fine, green, fern-like foliage and white flowers in spring.

G. buxifolia, gray spider flower, endemic to sandstone areas of New South Wales, is an open, rounded, bushy shrub, to 1.5 m (5 ft). The closely set leaves are oblong in shape and hairy, and the reddish brown flowers, borne in clusters, are also hairy, which gives them a grayish tinge.

G. x ga­udichaudii, a natural hybrid between G. acan­thifolia and G. laurifolia, is a very useful groundcover plant. It is a vigorous grower, with coarsely lobed, sharply pointed leaves and red-dish purple flowers of the toothbrush type, in spring and early summer. This species has been grafted onto G. robusta and the resulting weeping standard grevilleas make striking accents in the garden.

G. juniperina, zone 8, spider flower, from eastern Australia, is a very hardy plant, with bright green, spiky leaves and red or yellow flowers in spring and summer. It is generally a tall shrub, though there is a pros­trate form producing dull yellow flowers throughout most of the year.

G. lavandulacea, zone 8, also varies in form, but is commonly low growing with grayish foliage and bright red flowers. The Poorinda Hybrids include Beauty, with scarlet flowers in late winter; 'Constance', with orange-red flowers throughout most of the year; 'Elegance', with orange and pink flowers; 'Firebird', which grows 1-2 m (3-6 ft), with bright red flowers; 'Pink Coral', with pink flowers; 'Queen', with apricot wheel-shaped flowers; 'Signet', with deep pink flowers; 'Splendor', with silvery foliage and red flowers.

G. robusta, silky oak, from subtropical rain-forests of east coast Australia, grows to 30 m (100 ft) tall. The golden yellow, toothbrush-type flowers bloom profusely in summer, almost covering the dark green, fern-like foliage. The flowers are rich in nectar and the beautiful timber produced from these trees is used in cabinet-making. It is a popular tree for large gardens and parks in temperate climates.

G. rosmarinifolia, zone 8, rosemary grevillea or spider flower, is an attractive, useful shrub as it can be trimmed into a formal hedge. It grows to a height and spread of 2 m (6 ft). It has clus­ters of red, spider-like flowers with narrow, pointed leaves. Many forms are available.

G. thelemanniana has both an upright and a prostrate form, the latter being the more com­monly grown and available in two types, one with gray leaves and red flowers, the other with pale green foliage and softer red flowers. The gray-leafed form is more frost-tender. Both flower from late winter to spring.

G. tridenti­fera, to 2 m (6 ft), has attractive, three-lobed, pointed leaves and soft, feathery, white flowers. Many Grevillea cultivars are sold under their cultivar names only, such as Grevillea Toorinda Constance' or Grevillea 'Canberra Gem'. The label should describe their future size and flower colour. 'Robyn Gordon', with a height and spread of 1 m (3 ft), is probably the most commonly grown of all the cultivars. It pro­duces red flowers for many months of the year. Other popular shrubby cultivars include 'honey Gem', to 3 m (10 ft) high, with a spread of 2.5 m (8 ft), and rich gold flowers; 'Moonlight' to 2 m (6 ft) high and 3 m (10 ft) wide, with creamy white flowers; and 'Misty Pink' which reaches 3-4 m (10-13 ft) high. 'Bronze Rambler' is a useful grevillea cultivar widely used as a groundcover or spillover plant.

Cultivation

Propagate grevilleas from seed from the small, hooked capsules. The plant ejects the ripe seeds quickly, so tie a paper bag lightly around almost-ripe capsules to catch the seed. Seed may germinate erratically, some taking much longer than others. In favorable condi­tions, grevilleas will hybridize naturally but the plants produced may be sterile. These forms must be propagated from cuttings taken in summer or autumn from healthy tips, about 6-8 cm (2-3 in) long, cut just below the leaf nodes. Remove the leaves carefully from the lower two-thirds. For species with large leaves, it is advisable to reduce the remaining leaf area by about a third by cutting off the leaf tips. Strike cuttings in a mixture of two parts coarse, sharp sand to one part peat moss. Keep moist and shaded. When potting on the small, established plants, avoid root disturbance by first immers­ing them in water. Plant at the same depth as they were in the cutting mix in a mixture of sandy loam and leaf mould or peat moss, with an added teaspoon of blood, fish and bone per small pot. The plants can be potted on a second time as they harden up, before being planted out. Grevilleas need good drainage, slightly acidic soil and a warm position. Most species are relatively disease-free, except for scale pests which can be fairly easily controlled with a white oil spray. In cold and cool climates, grow in an airy, cool greenhouse or conservatory, in pots of acid potting compost and in maximum light. Grevilleas dislike a lot of phosphorus in the soil

Climate

Zone 9 (warmer parts), unless indicated below.