A shrub that typically grows to a height to 4.5 metres, often around 2 metres. It is found on sandstone – rocky habitats, in the Capertee and Goulburn River catchments, north-west of Sydney in the central tablelands and central western slopes divisions. There are also some unsubstantiated records from the south-coast of NSW.
Leaves are strongly divided (verging on pinnatisect) leaves to 25 cm long in outline. The leaves have between five and ten, erect, linear lobes, to 2 mm wide.
A grevillea inflorescence is technically a cluster of paired flowers, termed a conflorescence with the overall structure forming a raceme-like appearance. Grevillea species exhibit 3 main inflorescence structures:
1. A cylindrical to ovoid raceme (with flowers emerging around a 360° radius)
2. A single-sided raceme (with flowers produced on only one side, resembling a tooth-brush)
3. A condensed or clustered raceme (usually as long as it is wide, with species referred to as the spider-flowers)
Grevillea mostly produce the inflorescences at the terminals, beyond the foliage, which differs to the closely related Hakea.
This species is another of the spider-flowers with rich red-orange inflorescences, produced in spring. Some forms have cream tinges in the flowers and others are more orange in colour.
Individual flowers are composed of 1 carpel (female part) where the style and stigma protrude out; 4 stamens hidden away in the perianth; and the perianth (petals and sepals collectively) which connects to a pedicel. Proteaceae flowers do not have any discernible petals or sepals (having only one whorl) and so these are referred to as “tepals” of which there are 4.
The carpels are to 40 mm long, red-pink. The perianths have soft hairs in the base.
The fruit is a follicle, about 1 cm long, spherical, to 10 mm in diameter, containing one or two seeds.
Neil Marriot in the ANPS Grevillea study Group (Newsletter No 103) had the following to say about the different flowering forms of this plant:
“The common garden variety is the larger and far less showy red and cream flowered form which grows on the Brogo River on the south coast of NSW. It was this form that was originally introduced into cultivation by George Althofer in the 1950’s.
Suitable for a large garden where it attracts honeyeater birds.
The orange flowered form of Grevillea johnsonii is ‘undoubtedly one of the showiest of all the Eastern Grevillea species, but despite this fact it remains virtually unknown in cultivation.
It grows naturally in the Goulburn River catchment at Cox’s Gap and several other close by areas.
In a garden situation, once established it tolerates hot and dry summer conditions, cold, wet and frosty winters and sets copious quantities of seed which germinates readily once soaked in smoked water for 24 hours and sown in a well-drained mix.
Grevilleas are propagated by three principal methods; seed, cuttings and grafting. To maintain desirable characteristics of a particular plant, vegetative propagation (e.g. cuttings or grafting) must be used. This also applies to propagation of named cultivars.
They type specimen was collected near Kerrabee Mountain and the Sandy Hollow–Gulgong railway line in N.S.W. It is closely related to G. longistyla. However, differences are evident through the colour of G. johnsonii, ranging from orange to pink in comparison to the orange and red of G. longistyla.
Both species were initially listed as forms of G. longistyla, but have since been separated with a specific status.
Grevillea flowers were a traditional favourite among First Nations Peoples for their sweet nectar. This could be shaken onto the hand to enjoy, or into a coolamon with a little water to make a sweet drink. They might be referred to as the original “bush lollies”
G. johnsonii is capable of regenerating after fire from epicormic buds on the trunks and/or branches, from a basal lignotuber and as well regenerates from soil stored seed.
Grevillea – was named in honour of Charles Francis Greville (1749-1809), an 18th-century patron of botany and co-founder of the Royal Horticultural Society. He was also a British antiquarian, collector and politician who sat in the House of Commons from 1774 to 1790.
johnsonii – honours Lawrie Johnson who was the collector of the type material, “whose perceptive insights into the Australian flora have added considerably to our understanding of many plant families” He was an Australian taxonomic botanist who worked at the Royal Botanic Gardens, Sydney, for the whole of his professional career, as a botanist (1948–1985) and Director (1972–85).