Bossiaea leptacantha

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Bossiaea leptacantha

This species is one of the many small pea-flowers common to WA.  Bossiaea leptacantha is endemic to this State and frequently encountered in mallee country as far inland as the Norseman district (around 200 km or 125 miles) N of Esperance, plus a similar distance to the NW and NE, with a few records along near coastal areas on the Nullarbor.  From my observations it favours limestone, either exposed or covered in various fine sandy loams and is particularly common on the upper portion of limestone breakaways.

The simply divided branches of Bossiaea leptacantha originate from a central rootstock and radiate outwards to form a neat low dome and despite the foliage consisting of fine branches and scale-like leaves, it forms a moderately dense shrub to ½ metre x 1 metre diameter (18”x 36”).  It is a hardy, low rainfall, mallee region plant, often found in sizeable colonies in undulating open woodland, and being a highly distinctive species is unlikely to be confused with others in the Esperance district.

The branches are silvery green, slightly flattened and function as a leaf (cladode), whilst the tips are more rounded and have a point on the ends, which are a little prickly but not viscously so.  The numerous bright yellow flowers have broad upright standards and may occasionally have thin reddish striations.  These can bloom anytime between July and December, but are subject to local weather conditions.

Bossiaea is a member of the large and highly diverse Fabaceae family, although some authorities retain it under Papilionaceae, as do earlier references.

Bossiaea flexuosa – Zigzag Bossiaea

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Bossiaea flexuosa – Zigzag Bossiaea

This species has a conservation code Priority Three rating, meaning it is poorly known and currently only encountered in a few locations not under imminent threat. It has been found W and NW of Esperance from Young River to E of Hyden, then E to the Norseman region and S towards Salmon Gums (N of Esperance). In the colonies I have encountered, plants have been reasonably common, growing after fire in a sandy soil, probably over gravel between Fields Road and Lake Tay, but have also been recorded growing in deep sand elsewhere.

Bossiaea flexuosa is a low spreading shrub (to 60 cm or 2’ in height) commonly producing aerial shoots from a laterally expanding rhizome, which probably permits plant survival and fast regeneration following bushfire. The leaves are minute, bract-like and usually only seen on new foliage growth, but soon fall as the stem matures. The exaggerated flexuose (zigzag) stems, low habit and hairy calyx (cup below petals), easily distinguish this Bossiaea from other related species.

Flowers are produced anytime (depending on local rainfall) from September to November and from observations possibly (on occasion) August too. All Bossiaea plants (as with other pea-flowers) have in Western Australia been placed in the Fabaceae family, but may be listed elsewhere by other Authorities.

Bossiaea dentata - Elegant Bossiaea

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Bossiaea dentata - Elegant Bossiaea

This species is highly distinctive, being the only Bossiaea with opposite leaves, pendant flowers and a shorter standard petal than the wing and keel petals. In the Esperance region I have only encountered it within sight of the ocean, although in the Fitzgerald River National Park it can also be found a little further inland. Interestingly, it only occurs in three widely separated coastal regions between Albany and Cape Arid, which I suspect reflects its preference for non-calcareous soils, despite growing in beach sand east of Esperance.

The region between Cape Le Grand and Cape Arid (east of Esperance) was in a previous wetter period, a large floodplain where calcareous matter was leached from the soils including the beach area, to provide an unusual habitat for a variety of species. Bossiaea dentata is generally a bushy shrub from 1-2 metres (3’-6’), often growing into each other to form thick hedges against strong salt-laden sea-winds near the beach, elsewhere it can be encountered on granite outcrops and in rocky gullies.

The mostly red flowers (sometimes yellow/green) to 4 cm or (13/4”) overall length, like many other red pea-flower species are believed to attract pollinating birds especially the smaller varieties, who can feed safely and at the same time avoid predators and larger bullying birds amongst the dense foliage. Bossiaea dentata is a spasmodic flowering species and has been recorded from May to November, often producing flushes of blossom during the period probably determined by the amount of seepage into their habitat after rainfall.

Bossiaea barbarae – Barbara’s Bossiaea

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Bossiaea barbarae – Barbara’s Bossiaea

In Western Australia the genus Bossiaea is now (due to a newly adopted classification system) been placed into the Fabaceae family, but may still be contained in Papilionaceae or Leguminodae elsewhere. Bossiaeas are widely distributed in Australia particularly in southern parts, with WA having around 45 species (38 described), which is considerably more than the rest of the country. The WA ones were reviewed in 2006 by Dr. J. H. Ross who described 14 new species of which Bossiaea barbarae is one. It is named after Barbara Archer who is a substantial botanical collector from Norseman (200 km or 125 miles north of Esperance).

Bossiaea barbarae has been found from Esperance to Norseman, plus NW of Hyden, whilst the plants above were encountered at the intersection of Rockhole Road and the Oldfield River, which is centrally sited between these groupings. It is not a threatened species, but like many pea-flowers it appreciates periodic bushfires to reduce larger vegetation and stimulate seed germination, otherwise it will temporally disappear and therefore cannot be recorded. It grows in sandy loams around saltlakes and in this case above a brackish river, which seems to indicate a liking for mild saline conditions.

This species spreads from a central root system to periodically produce vertical stems of around ½ metre (18”) in height. It is quite prickly by having numerous small side-branches that end in a sharp point, these generally have small blue/green leaves each side and appear to be pinnate, but there is no specific arrangement. Nevertheless the leaves are an important identification feature, by being flat (no recurved edges) and having a pronounced central rib on the underside. Also as already mentioned, they are glaucous (blue/green).

The flowers although not especially large (less than 1 cm or 3/8” diameter) are numerous and colourful, thereby providing a pleasing display from August to October.

Cactus Pea - Bossiaea walkeri

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Cactus Pea - Bossiaea walkeri

Bossiaea walkeri is a mallee shrub commonly growing between 1.5 and 3 metres (5-10’) in height and usually found inland except where the mallee vegetation comes down to the coast just north of Israelite Bay (190 km or 120 miles ENE of Esperance). The average annual rainfall in the mallee region is between 30-40 cm (12”-16”), which although winter dominant can be highly irregular, making many plants very opportunistic in order to take advantage of passing storms by quickly coming into flower after soaking rain. Nationally, the Cactus Pea is also found in similar mallee habitats (although often rare) in parts of SA, Victoria and NSW, although soils vary over its range.

Locally, Bossiaea walkeri is commonly found around low-lying granite outcrops, growing in the fine sand/clay loam over limestone and/or granite, here it favours the open area between the eucalypts and the open granite zone. These areas are very common to the NE of Esperance, where this plant is most plentiful. Interestingly, the leaves of the Cactus Pea are reduced to tiny scales and what look like waxy grey/green leaves, are actually flattened stems called cladodes that carry out a similar function to a leaf. In the hot and often prolonged dry mallee conditions, these stems are more hardy than leaves by reducing water loss and the need to replace stressed fallen leaves, plus they perform photosynthesis, respiration and transpiration.

The 2 cm (nearly 1”) long orange/red flowers are produced anytime between July and November and will often flower after seed has set to take advantage of additional rainfall following a dry period. Birds are the primary pollinators, although small mammals and insects probably also play a role. The seedpods are initially green, but mature to a bronze/brown that on a hot day will explode to propel the seed several metres.

Bossiaea preissii - Fabaceae

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Bossiaea preissii - Fabaceae

A common shrub to 1 metre (around 3') that gos largely unnoticed until it comes into flower, when it then screams its presence with brilliant 1.5 cm (over 1/2") long scarlet flowers. It is a reasonably open shrub with small green leaves and a sharp spike terminating most branches (easily avoided with a little care). This is one of the pea-flowers that attracts honeyeating birds, which is probably the reason for its colorful display. Bossiaeas typically have a long narrow flower making identification relatively easy.

This Bossiaea is usually found in low-lying sandy heath with light seepage, also it will contentedly grow in semi-shade amongst larger shrubs and tall sedges. However, they will also thrive in more exposed locations providing the soil is cool and moist as is encountered on low sandy rises along flood plains, or run-off from rocky slopes.

Flowering is from April to October, with June and July usually providing the best displays.

Update 1/03/10
The WA Herbarium has recently amended their classification of several flora families in line with current common practise. In this instance the Papilionaceae family is changed to Fabaceae. There are no changes to genera or species as a result of this update.

Update 4/04/2010
Two photographs added showing a bright yellow flowering form, it was discovered in September near Quagi Beach 55 km (34 miles) west of Esperance. Here it was common although localised growing in a white sand (probably non-calcareous due to leeching) over limestone.