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An erect shrub to a height of 2 metres, spreading to 1 metre wide, with flattened hairs on the stems.
It has an occurrence mainly in NSW, in some disjunct patches, growing in the greater Sydney area (usually on clay soils), to as far south as Goulburn-Bungonia and east to Nowra; through Wollongong and western Sydney (making a good show in Sydney’s Cumberland Plain Woodland), then from Bathurst through to Dubbo, as well as west of Newcastle. It is found again to the west and east of Tamworth, with many plants found between Armidale, north to Gympie (and further west) in Queensland.
It is typically found in dry sclerophyll woodland and forests, on heavier soils (clay-based).
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 linear, needle-shaped and sharply-pointed, to 20 mm long and less than 1 mm wide, trigonos in cross-section and with a yellow-ish petiole at the base of mid to dark green leaves. The plant is prickly overall.
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 are arranged in racemes of up to 10, in leaf axils near the ends of branchlets, yellow to yellow-orange in colour, with the standard to 10 mm long and bearing red markings, occurring from April to November.
The fruit of all peas is a pod. In this species, they are approximately 5 mm long with the seeds smooth.
A very nice, if prickly shrub, but it is unknown how readily it is cultivated. It usually grows naturally on clay soils and so may need this to thrive. It would be well worth growing as a garden pea. Check with local native nurseries for availability.
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.
Monitor closely as seeds released immediately or within 1-2 days of maturity. Seeds have long storage life.
Cuttings strike reasonably well using firm, current season’s growth.
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 stabilise 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:
https://en.wikipedia.org/wiki/Dillwynia
Dillwynia spp. will mostly regenerate from seed after fire.
Dillwynia – honours Lewis Weston Dillwyn (1778-1855) who was a British porcelain manufacturer, naturalist and Whig Member of Parliament (MP). He was also renowned for his published works on botany and conchology.
sieberi – after F.W.Sieber (1789-1844) an early nineteenth-century Czech botanist. He collected plants in Sydney over 6 months in 1823, as well as many other places world-wide. He has many plants named after him and also published many Australian species.
This species is not considered to be at risk of extinction in the wild.
NSW Flora Online (PlantNET) – Dillwynia sieberi profile page
https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Dillwynia~sieberi
Wikipedia – Dillwynia sieberi profile page
https://en.wikipedia.org/wiki/Dillwynia_sieberi