Eutaxia parvifolia – Fabaceae

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Eutaxia parvifolia – Fabaceae

The Eutaxia genus has been a very confusing group of plants, as many species are very similar to each other and require close inspection to separate. In the WA eastern distribution of this species, Eutaxia parvifolia is very similar to Eutaxia microphylla and has been misidentified as such for some time. However the differences between these species have now been clarified by Wilkins, Chappill and Henderson in their manuscript ‘An account of Eutaxia with a focus on the Western Australian species’, where they now conclude Eutaxia microphylla does not occur in Western Australia

The most obvious difference between these species is in the size and structure of the leaves, with Eutaxia parvifolia having a distinct petiole (stalk), highly variable sized leaves (length) on the same plant and at least one noticeable vein on the underside. Eutaxia microphylla leaves are either sessile (no stalk) or have a very short petiole to 0.2 mm, more consistently smaller sized leaves 2.3-4 mm long, plus have no visible veins. The distribution of Eutaxia parvifolia is from the north of Perth to Cape Arid (east of Esperance), then spreading in scattered colonies to the Albany region, where common to the west of the town.

Eutaxia parvifolia is sparsely scattered to the east of Esperance, but where it does occur it can be in considerable numbers, in one instance forming an extensive carpet of around 100 metres/yards square and to 60 cm (24”) in height. Locally this species favourers sandy loams over clay, where there is slow sub-surface water movement, which tend to be around rarely flooding Yate Swamps (Eucalyptus occidentalis). These environments are mostly within 50 km (30 miles) of the coast. Further inland (over 100 km) there is another similar looking species called Eutaxia actinophylla, but the leaves of this species are in whorls of three, instead of paired as with E. parvifolia.

Like many peaflowers Eutaxia parvifolia is visually appealing, when their bright red/yellow flowers are produced in great profusion between August and December, although locally with our lower rainfall and warmer conditions, flowers have usually finished by November.

Eutaxia myrtifolia

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Eutaxia myrtifolia

Eutaxia myrtifolia was previously known as Eutaxia obovata and is a highly adaptable widespread species, occurring from east of Esperance to the SW corner of Western Australia. In the Esperance region it is most commonly found on near coastal granite outcrops where annual rainfall is above 50 cm (1’6”), further west where rainfall is higher, it is also encountered in other habitats. Eutaxia myrtifolia can grow to over 2 metres (7’) in height, but locally is little more than half that size.

Around Esperance, soils on granite outcrops are usually sand, gravel or limestone over the granite and receive rainwater run-off from above, but as photographs show, Eutaxia myrtifolia will grow very close to the coast and is periodically subjected to salt-laden gale force winds during winter/spring. Nevertheless it is able to tolerate these harsh environmental conditions, by having thick, waxy, myrtle-shaped leaves that are neatly arranged along the branches. When the soils are deeper with good run-off, the foliage remains an attractive green, but if the plant is growing in dry conditions, it can become yellowish and might die unless there is greater rainfall. This indicates the limitations of this otherwise very tough shrub and why it does not occur in drier conditions further inland.

The flowers are bright and prolific providing Eutaxia myrtifolia with attractive displays, which locally are mainly produced during spring, however variable weather conditions can encourage or delay flowering as is evidenced by herbarium records of February, plus May to December.