The Versatile Grevillea - An Australian Wildflower
With 340-odd species and subspecies of grevillea cluttering up Australia's bush and gardens plus hundreds of hybrids, there must surely be a grevillea to suit every gardener's requirement. It is one of the most widespread of Australia's native plants and is found in the tropics of the north, the deserts of the centre, the alpine areas of the Great Dividing Range and the temperate areas of Tasmania.
The genus name commemorates Charles Francis Greville (1749 – 1809), a British antiquarian and collector who founded the Royal Horticultural Society. Greville was a friend of the botanist, Sir Joseph Banks, who came to Australia with Captain Cook.
Apart from a few grevilleas which are endemic to Melanesian areas, the plant is confined to Australia although it now has fans in many other temperate and subtropical areas. Three species are endemic to New Caledonia while both Sulawesi and New Guinea each have a native species. Two other species occur in both New Guinea and Queensland.
Grevilleas belong to the family Proteaceae or protea family and are closely related to the genus Hakea.
Proteus was a Greek god from whose name the Protea family evolved. He was noted for his ability to change his appearance and form as he wished. And so it is with the grevillea. Species range from prostrate ground-covers to small shrubs and up to large trees. The colour and structure of the blossoms, the size and shape of the leaves are so varied that it is hard sometimes to see the relationship between two species. However, common to the grevilleas is the fact that they are woody evergreen plants with (generally) intricate and stunningly distinctive flowers. The flower heads of the grevillea open at varying times and are composed of many small flowers. Most common shades are yellow, orange and red. The styles are long and filament-like. Leaves vary from needle-like to fern-like.
All are noted for their beauty while some provide a very attractive timber for wood-working enthusiasts. One of the earliest examples of furniture made from grevillea is a Pembroke table which was made in the 1790s for Sir Andrew Snape Hamond, the Commissioner of the Royal Navy. Grevillea wood veneer was used on this small table, which has two drawers and folding sides. The table can now be seen in Canberra at the National Museum of Australia.
Many grevilleas have nectar-laden flowers, attracting birds, insects and animals to a sweet feast. One or other of the species will be flowering in every season of the year.
Grevilleas interbreed freely and this has led to the creation and commercial release of many hybrids. The three groups of hybrids are each derived from a limited range of parent species. No group shares parents with another group. The groups are Banksias (large, brush-like flowers), Rosmarinifolias (spider-like flowers) and Toothbrush (would you believe it, flowers like toothbrushes!). A few have been placed in a 'Miscellaneous' group – always a good standby for anything that doesn't fit anywhere else!
Being such a diverse group means that there is a wide range of conditions under which they will grow. As a general rule, grevilleas like a sunny, dry position. Western Australian species in particular are highly sensitive to phosphorous and fertilisers need to be chosen with this point in mind. Some professionals recommend that grevilleas not be fertilised. They have their own sophisticated root system which is very efficient at finding nutrients. It's best not to plant them near plants or lawns that are regularly fertilised.
Don't plant where water tends to sit and/or doesn't drain. Most don't like their roots constantly wet. They may not do well near lawns for this reason. If the soil isn't reasonably free-draining, plant on a slope or in a raised garden bed. Water for the first summer but then water only when really necessary.
Grevilleas have a multitude of surface roots and won't cope with excessive cultivation round the base of the plant. If placing mulch or organic fertiliser round the base of grevilleas, keep it back from the stem or trunk as it can cause rotting.
Plant varieties that suit the climate and soil conditions in your area.
Prune after flowering. This isn't essential but will result in a neater, tidier bush which will flower more profusely the following season and probably live longer than would otherwise be the case.
The soil should also be light, gritty and free-draining. Occasional deep watering will enhance flowering and promote more healthy foliage but the plants are remarkably drought-tolerant once established. Most are frost hardy down to 20oF. Regular pruning after flowering will rejuvenate the plant.
Grevilleas can be propagated from half-hardened cuttings or raised from seed. Many harder to grow species are grafted onto tough rootstock. G.robusta (Silky Oak) is often used as rootstock.
The follicles of the grevillea have a rather leathery texture. They are not produced in cones. As soon as the follicle matures, it splits to release the seeds. If you wish to collect seed to grow, you might like to try placing a nylon stocking over the ripening seeds. The stocking should be fine enough to allow light and air to reach the fruits. As the seeds mature and are shed, they will be held in the stocking for later collection.
Australian aborigines enjoyed the sweet nectar from the bush grevilleas. The nectar was shaken into the hand or into a receptacle before being drunk. Some commonly cultivated species produce flowers containing cyanide.
Honeyeaters in particular are common visitors to the flowers of the grevillea. Larvae of some Lepidoptera species such as the Dryandra moth utilise grevillea as food.
And finally, a few recommendations for particular purposes:
Tropical areas: Plenty of choice but good ones are Grevillea Formosa, G. Moonlight, G. Honey Gem, G. Misty Pink, G. longistyla.
Arid/Desert areas: G. Excelsoir, G. Petrophiloides, G. Eriostachya.
Frost Tolerant: G. Excelsior, G.Juncifolia, G. Rosmarinifolia, G. Thelemanniana, G. diminuta.
Tree-size grevilleas: G.banksii, G. Robusta (Silky Oak), G. longistyla, G. asparagoides, G. Pink Pearl.
Prostrate/Groundcover types: G. laurifolia, G. repens (Creeping Grevillea), G. ilicifolia - prostrate form (Holly Grevillea), G. glabrata, G.x gaudichaudii.
Bird-attracting varieties: G. asparagoides, Grevillea shiressii (Blue Grevillea), G. Pink Pearl, G. Poorinda Constance, G. jephcottii (Green Grevillea).
These are such attractive plants that everyone should at least have a try at growing grevilleas. You'll get so much pleasure from the flowers and garden birds will think they've gone to heaven.