Grevillea diffusa

Family: Proteaceae

A spreading shrub to 2 metres tall.

It is confined to the central coast subdivision of NSW, occurring north of the surrounds of Wollongong, to north of Gosford and west to Wentworth Falls, with some records near Kandos. Most records are in the Royal NP and around Mt White and Calga. It grows in dry forest and woodland, occasionally in swampy heath, usually on Hawkesbury sandstone.

3 subspecies are recognised (see notes below).

Leaves alternate along the stems, to 13 cm long and to 1 cm wide, margins entire and curved to rolled down, lower surface with silvery silky hairs. Leaves have a generally elliptic to narrow-oblanceolate to linear shape.

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 dark red / burgundy to scarlet inflorescences (rarely, they can be greenish-brown). Flowers occur in winter to spring and inflorescences can be dense to loose.

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 1 cm long; red to dark burgundy, sharply curved at the tips.
Perianths dark red / burgundy to greenish-brown.

The fruit is a follicle, about 1 cm long and hairless.

In the garden

Not a great deal of information can be found about its cultivation potential. However, it is reported to be hardy and reliable in most soils in full sun. Attractive in flower especially subsp. filipendula.
The deep burgundy flowers of some forms is a big attraction. Provide good drainage. Prune to shape as desired and to promote flowering. In a garden situation. Grevilleas are good bird-attracting plants.

Propagation

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.

Other information

There are three subspecies currently recognised:
subsp. diffusa:  leaves generally shorter, to 6 cm long, with inflorescences more dense. Generally occurring south of Sydney CBD.
subsp. constablei:  leaves to 7 cm long, perianth and carpels crimson to dark burgundy, with branchlets spreading. Occurring almost purely in Royal National Park Estate
subsp. filipendula:  leaves to 15 cm long, perianth and carpels scarlet to light burgundy, branchlets orientated to one side (secund). Occurring north of Sydney CBD.

Most Grevillea species will regenerate from seed after fire but can produce coppicing shoots. This species can be observed to be prolific after fire.

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”.

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.

diffusa – Latin – meaning loosely branching or spreading.

Not considered at risk in the wild.

https://en.wikipedia.org/wiki/Grevillea
https://apps.lucidcentral.org/plants_se_nsw/text/entities/grevillea_diffusa.htm
https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Grevillea~diffusa