An erect shrub to a height of about 1 metre, spreading to over 0.5 metres wide, with stems covered with shortly-curved hairs.
It mainly occurs in the Sydney area, on the Cumberland Plain but also further afield. Occurrences include as far north-west as Kurrajong Heights, as well as Falconbridge-Hazelbrook in the Blue Mountains. It has large populations in western Sydney, especially in the nature reserves on the Cumberland Plain. It extends up from Windsor, towards Wisemans Ferry, and as far south as Liverpool. Disjunct occurrences are also known from near Morisset, as well as the Bulga Mountains near Broke.
It is typically found in dry sclerophyll woodland and forest, on clay to alluvial soils, especially the Cooks River Castlereagh Ironbark Forests and Shale-Gravel Transition Forests.
It is a listed threatened species.
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, glabrous or sometimes hairy near the tip, to 12 mm long and less than 1 mm wide, often soft and weeping; mid to dark green in colour. The foliage has an overall soft feel.
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, orange-yellow flowers are usually arranged singly or in pairs, in leaf axils or on the ends of branchlets, with the standard to 10 mm long, bearing striking red markings, occurring from February to March but also at other times.
The fruit of all peas is a pod. In this species, they are approximately 5 mm long with a reticulate pattern on the seeds.
Not a lot is currently known about this species in cultivation, likely due to its rare nature. It could possibly be propagated but may be short lived. Grows naturally on clay to alluvial-gravel soils.
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.
Both the singular orange flowers and, the stem hairs, distinguish it from the similar and more common yellow-flowered Dillwynia glaberrima and D. floribunda.
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.
Dillwynias are often colonising species germinating quickly after fires to stabilise the soil and 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. (The Editor has observed this species regenerating after fire in large numbers, in the Western Sydney nature reserves).
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.
tenuifolia – from Latin tenuis – meaning “thin” or “fine” and –folia meaning “leaves”, referring to the thin and soft leaves of this species.
This species is listed as threatened with extinction at the State level with the category of vulnerable.
Australia Native Plants Society Australia – Dillwynia tenuifolia profile page
NSW Office of Environment and Heritage – Threatened Species Profiles – Dillwynia tenuifolia profile page
NSW Flora Online (PlantNET) – Dillwynia tenuifolia profile page