A usually upright shrub to 3 metres high (prostrate in some habitats), spreading to over 1 metre wide, with stems covered in short hairs.
It is a recognised species-complex with a range of forms. It is accepted as growing naturally in NSW and Queensland only, north from about the ACT and further east, with high concentrations of records from Jervis Bay and further north along the coast, through Sydney and the Blue Mountains, to as far west as around Orange, then in scattered patches along the western slopes, tablelands and coast, to Fraser Island and Hervey Bay, and inland in Carnarvon National Park, in Queensland.
It grows in heath, shrubland, dry sclerophyll woodland and forest, usually on sandstone or sandy soils.
Dillwynia is a member of the “pea” family. This generally means that leaves are alternate with stipules at the base of the petioles. Dillwynia have simple and alternate leaves, with stipules present and minute, or absent.
Leaves can be flat, terete or triangular in cross-section and often twisted.
In this species, leaves are crowded along the stems; linear, spirally twisted and smooth with the upper surface grooved, 15 mm long and only 1 mm wide. The foliage is smooth and soft to touch.
Flowers are, of course, pea-shaped (a term sometimes used is papilionate), with 5 petals in a fixed arrangement; the main back petal is called the “standard”, two lateral petals called “wings” and two fused petals at the bottom called the “keel” (in which the anthers and one carpel tend to be hidden).
In Dillwynia, flowers are yellow, or red and yellow (or orange/yellow) and are usually arranged singly or in small groups in leaf axils or on the ends of branchlets. The upper two of five sepal lobes are joined in a single “lip”. The standard petal is typically wider than high (a useful identification feature), and the keel is the same length as the wings. There are very small leafy bracts present on the common peduncle (which can fall early or be persistent) and bracteoles on flower pedicels (below the calyx).
In this species, flowers can be produced singularly, or are in umbel- or raceme-like clusters, at the terminals and upper leaf axils, with up to 9 flowers per cluster; yellow in colour, with the standard to 12 mm long and bearing red markings, occurring from June to November.
The fruit of all peas is a pod. In this species, they are approximately 7 mm long, with seeds smooth.
This species is amongst the few known to be cultivated to some degree. It is an attractive shrub when in full flower. It prefers a sandy soil and a part-shade habitat. It may die quickly due to wet soil or root infection. Can be a very nice shrub if it can be established successfully. Verys uited to sandstone-based gardens.
In a garden situation, Dillwynias are not overly common in cultivation and only occasionally grown by enthusiasts. They are generally suited to well drained soils in a sunny or semi-shaded position and most will tolerate heavy pruning.
Propagation from seed is relatively easy following pre-treatment to break the physical dormancy provided by the impervious seed coat. Pre-treatment can be carried out by abrasion or soak in near-boiling water for about 30 seconds, before cooling rapidly under flowing cold water. Alternatively soak in cold water for several hours. Dry to prevent rotting before sowing. Germination occurs in 3-4 weeks.
Cuttings strike reasonably well using firm, current season’s growth.
Seed is available commercially.
This complex includes at least two species that grow together on Hawkesbury sandstone in the Sydney region. Other regional variants may belong to additional distinct taxa. The complex is under taxonomic revision.
Dillwynia is a genus of about 40 species of flowering plants endemic to Australia and occurring in all Australian states and the Australian Capital Territory (except the Northern Territory). They are generally small to medium-sized shrubs. They are often known by the name of ‘Eggs and Bacon’ or ‘Parrot-peas’ because of their bright yellow and reddish tints of the flowers. NSW currently has about 22 taxa.
Dillwynia plants (as well as Acacia) are often colonising species which germinate quickly after fires to stabilize the soil and to provide nitrogen (all are legumes able to “fix” nitrogen from the atmosphere in nodules on their roots).
The following link is a list of Dillwynia species accepted by the Australian Plant Census and Plants of the World Online as at May 2021:
Dillwynia spp. will mostly regenerate from seed after fire.
Dillwynia – honours Lewis Weston Dillwyn (1778-1855) was a British porcelain manufacturer, naturalist and Whig Member of Parliament (MP). He was also renowned for his published works on botany and conchology.
retorta – Latin – retortus meaning “twisted” – referring to its leaves.
This species is not considered to be at risk of extinction in the wild.
Australian Plants Society – Sutherland. Coastal Plants of the Royal National Park CD – Dillwynia retorta profile page
NSW Flora Online (PlantNET) – Dillwynia retorta profile page
Wikipedia – Dillwynia retorta profile page
Cronin, L. (1990). Key Guide to Australian Wildflowers. Reed Books Pty Ltd.
Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.