Grevillea diffusa explained

Grevillea diffusa is a species of flowering plant in the family Proteaceae and is endemic to the Sydney region of New South Wales. It is a low, compact shrub with elliptic to linear leaves, and dark red, or dark crimson to scarlet and burgundy-coloured flowers.

Description

Grevillea diffusa is compact shrub that typically grows to a height of up to but sometimes an erect shrub to . The leaves are elliptic to lance-shaped with the narrower end towards the base, or linear, long and wide, the lower surface silky-hairy and the edges curved down or rolled under. The flowers are arranged in dome-shaped to more or less spherical groups and are dark red, dark crimson to burgundy-coloured or scarlet, depending on subspecies. The pistil is usually long and the style strongly curved and more or less glabrous. Flowering occurs from July to November and the fruit is a glabrous follicle.^{[1] [2] [3] [4]}

Taxonomy

Grevillea diffusa was first formally described in 1827 by Kurt Polycarp Joachim Sprengel in Systema Vegetabilium from an unpublished description by Sieber.^{[5] [6]} The specific epithet (diffusa) means "spread out".^[7]

In 1986, Donald McGillivray described subspecies of G. diffusa in his book New Names in Grevillea (Proteaceae), and in 2000 Robert Owen Makinson described subspecies in Flora of Australia, and the following three names are accepted by the Australian Plant Census:

• Grevillea diffusa subsp. constablei Makinson^[8] has narrowly elliptic to more or less linear leaves mostly long and wide, peduncles less than long and dark crimson to dark burgundy-coloured flowers;^{[9] [10]}
• Grevillea diffusa Sieber ex Spreng. subsp. diffusa^[11] has elliptic leaves long and wide, peduncles up to long and dark red flowers;^{[12] [13]}
• Grevillea diffusa subsp. filipendula McGill.^[14] has narrowly elliptic to more or less linear leaves mostly long and wide, peduncles long and scarlet to light burgundy-coloured flowers.^{[15] [16]}

Distribution and habitat

This grevillea grows in forest or woodland, occasionally in swampy heath and is restricted to Hawkesbury sandstone in the Sydney basin. Subspecies constablei is found south of Sydney from Waterfall to Helensburgh and near the Georges River, subspecies diffusa from the lower Georges River to the Illawarra region and subspecies filipendula between Calga and Mount White, north of Sydney.

Conservation status

Grevillea diffusa has been listed as Least Concern on the IUCN Red List of Threatened Species. Although its distribution is restricted, the population of this species is presumed to be stable and there are currently no major threats impacting it. Increased fire regimes may pose a minor threat in some areas of its distribution.^[17]

Notes and References

1. Web site: Makinson . Robert O. . Grevillea diffusa . Australian Biological Resources Study, Department of Agriculture, Water and the Environment . 25 March 2022.
2. Web site: Makinson . Robert O. . Grevillea diffusa . Royal Botanic Garden Sydney . 25 March 2022.
3. Web site: Wood . Betty . Grevillea diffusa . Lucid Keys . 25 March 2022.
4. Book: Fairley . Alan . Moore . Philip . Native plants of the Sydney district : an identification guide . 1989 . Kangaroo Press in association with the Society for Growing Australian Plants-NSW . Kenthurst . 0864172613 . 170.
5. Web site: Grevillea diffusa. APNI. 25 March 2022.
6. Sprengel . Kurt P.J. . Curae Posteriores. . Systema Vegetabilium . 1827 . 17 . 4 . 2 . 46 . 25 March 2022.
7. Book: Sharr . Francis Aubi . George . Alex . Western Australian Plant Names and Their Meanings . 2019 . Four Gables Press . Kardinya, WA . 9780958034180 . 183 . 3rd.
8. Web site: Grevillea diffusa subsp. constablei . Australian Plant Census . 25 March 2022.
9. Web site: Makinson . Robert O. . Grevillea diffusa subsp. constablei . Australian Biological Resources Study, Department of Agriculture, Water and the Environment . 25 March 2022.
10. Web site: Makinson . Robert O. . Grevillea diffusa subsp. constablei . Royal Botanic Garden Sydney . 25 March 2022.
11. Web site: Grevillea diffusa subsp. diffusa . Australian Plant Census . 25 March 2022.
12. Web site: Makinson . Robert O. . Grevillea diffusa subsp. diffusa . Australian Biological Resources Study, Department of Agriculture, Water and the Environment . 25 March 2022.
13. Web site: Makinson . Robert O. . Grevillea diffusa subsp. diffusa . Royal Botanic Garden Sydney . 25 March 2022.
14. Web site: Grevillea diffusa subsp. filipendula . Australian Plant Census . 25 March 2022.
15. Web site: Makinson . Robert O. . Grevillea diffusa subsp. filipendula . Australian Biological Resources Study, Department of Agriculture, Water and the Environment . 25 March 2022.
16. Web site: Makinson . Robert O. . Grevillea diffusa subsp. filipendula . Royal Botanic Garden Sydney . 25 March 2022.
17. Makinson, R. . Auld, T. . 2020 . Grevillea diffusa . 2020 . e.T112652020A113309305 . 10.2305/IUCN.UK.2020-2.RLTS.T112652020A113309305.en . 30 December 2023.