Gompholobium baxteri - Baxter’s Wedge-pea

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Gompholobium baxteri - Baxter’s Wedge-pea

This plant can be very confusing and easily thought to be two species. One form occurs in the inland mallee and has single leaves, whilst the other is found in coastal heath and has trifoliate leaves. However the canary yellow flowers, viscid buds, hairy seedpods, etc, are identical to both and hence these plants are technically the same species. The mallee form also tends to be much bushier, thereby giving these shrubs a markedly different appearance.

Both forms grow in non-calcareous sandy soils, although at least locally, the coastal form occupies low-lying areas, often around swamps or light seepage zones where the soil would retail moisture for longer periods. Interestingly, there is a very similar looking plant (Gompholobium tomentosum) with slightly smaller and paler yellow flowers, plus the leaves are divided into several leaflets. This plant in undulating country grows immediately above G. baxteri (within a metre/yard), to then exclusively extend to the summit of the sandy mound/hill. It is almost like these species are two opposing sides, with neither crossing over an invisible barrier.

Conversely, mallee forms tend to occupy the higher sandy slopes, but these are often yellow coloured and probably contain additional nutrients compared to the lighter coastal sands. Nevertheless, the mallee environment would be drier and warmer and the single leaf form probably is an adaptation to these conditions. Like peaflowers generally, these plants do very well following bushfires, when there is considerable germination and rapid growth as they take advantage of the more open and ash fertilised conditions. However, after a few years the slower growing, but taller vegetation will eventually push them out.

Gompholobium baxteri, named after an early botanical plant collector is very common and grows in near coastal areas between Ravensthorpe and Israelite Bay and to around 150 km (90 miles) inland. The brightly coloured flowers are produced between August and December and although local weather conditions will influence exactly when, these plants do produce blossom over a long period, providing adequate moisture is available.

Gompholobium is part of the very large and highly diverse Fabaceae family, which includes all legume species, including Acacia. Depending on the classification system in use, Gompholobium may also be listed under Papilionaceae or Leguminosae.

Gompholobium knightianum

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Gompholobium knightianum

This is a delicate little rambling plant, commonly less than 60 cm (2’) diameter. It is very widespread, growing after fire or soil disturbance and often found along slashed bush tracks, or in natural clearings. It occurs from Israelite Bay (East of Esperance) to the Geraldton region (North of Perth) and is generally within 100 km of the coast, where it favours heath and/or open woodland.

Soils can be deep non-calcareous sand or gravel, with little concern for location providing the soils are reasonably well-drained. Like most Gompholobium species, the flowers are comparatively large and colourful, but despite those features, plants in this genus are named after their distinctive globular pods.

Individual leaves of Gompholobium knightianum are made of up of several pairs of leaflets, plus a terminal one (imparipinnate), which can vary considerably in length and width, with basal (earlier) foliage being shorter, broader and with fewer leaflets. An important distinction between Gompholobium knightianum and other pink flowering Gompholobium species is with the leaflets, which are quite flat with G. knightianum, thereby making it easy to identify in the field.

Gompholobium knightianum is a long flowering species, producing additional flowers in the top leaf junctions of growing branchlets. These comprise racemes of 4-8 pink/purple flowers, which depending on distribution and local weather conditions can bloom from July to December.

Gompholobium is part of the very large and highly diverse Fabaceae family, but depending on the classification system in use, may be listed under Papilionaceae or Leguminosae elsewhere.

Reference:

Taxonomic revision of Gompholobium (Leguminosae: Mirbelieae)

By JA Chappill, CF Wilkins and MD Crisp

Australian Systematic Botany Vol 21

Gompholobium scabrum - Painted Lady

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Gompholobium scabrum - Painted Lady

This pea-flower from the Fabaceae family, would be one of the most spectacular with large brightly coloured pink/purple/red flowers and well deserving its common name of Painted Lady, but when not in bloom these plants would not attract a second glance as they are insignificant and dissolve into the background. Gompholobium scabrum is widespread, ranging from north of Perth to east of Esperance, but although collectively common, locally they are usually found in small groups or scattered individuals
Around Esperance it favours a heath habitat in moderately flat non-calcareous sandy soil over weathered clay and coastal limestone, so would be slow draining and retain moisture for extended periods. In these windswept environments, the vegetation is undulating to around a metre (3’) in height, from which Gompholobium scabrum just protrudes.
Most Gompholobium plants produce 4 seeds per pod and once were the only members of this genus, but G. scabrum and several others have just 2 seeds per pod. This feature was initially used to place them into different genera, the other called Burtonia, so Gompholobium scabrum was previously known as Burtonia scabrum (now discarded).
The foliage is only about 1/2 cm (1/4”) in length, but are digitate (leaf lobes coming from a central axis, like fingers from a hand), whilst the prolific number of flowers are around 2 cm (3/4”) diameter. The flowering period is recorded from August to November, but weather conditions determine whether they bloom earlier or later, although the months of September/October are reasonably reliable.

Gompholobium polymorphum – Twining Gompholobium

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Gompholobium polymorphum – Twining Gompholobium

This large colourful pea-flower from the Fabaceae family, twines and climbs on neighbouring vegetation to around 1 metre (over 3’) in height. However, it is rarely noticed except when its 2 cm (3/4”) diameter flowers, with their bright splashes of color come into bloom. These are designed to attract a pollinator, but will do the same for any wandering person passing by.

Gompholobium flowers tend to be quite chunky and very eye-catching, with their clean bright colours and rounded shape. The leaves of most species are compound, either pinnate or as in this case digitate (hand and fingers like); Gompholobium polymorphum as its name suggests can be quite variable, with the digits differing  in length and width, but around Esperance they are mostly linear as shown above. As this species is widely distributed from east of Esperance to north of Perth it probably has several local forms.

Gompholobium polymorphum favours gravel soils, particularly around granite outcrops, where rainfall run-off would supply additional moisture to help it over its locally late flowering season from November to January, although they are recorded blooming from September. This species is also known to produce totally yellow flowers, but I have not seen them around Esperance.

Gompholobium conferta - Fabaceae

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Gompholobium conferta - Fabaceae

Previously known as Burtonia conferta, it is a widespread shrub of less than a metre (usually under 3') in height, but seldom occurs in large colonies. It is however often pleasurably encountered accidentally when in flower, in sandy heathland, around granite outcrops or gravel pits, but otherwise gos mostly unnoticed.

Gompholobium conferta is usually an open shrub, with upright stems that are densely clothed in narrow-linear leaves to 2 cm (3/4") in length. Interestingly, Gompholobium leaves are mostly deeply divided into leaflets (some need close examination to distinguish this feature), but G. conferta is one of the few with undivided leaves. The eye-catching blue/purple blooms are unmistakable by their many flowered heads that are 5 cm (2") or more in diameter.

Recorded flowering from August to March, but this is from plants spread over nearly 1000 kilometres (620 miles), from Israelite Bay (east of Esperance) to north of Perth (almost to Geraldton). In the Esperance district, November to February would be more the norm.

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.