Gastrolobium punctatum

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Gastrolobium punctatum

This species along with a number of others were transferred to Gastrolobium from the Nemcia genus in 2002, which was detailed in a review titled Monograph of Gastrolobium (Fabaceae: Mirbelieae) by GT Chandler et al. I mention this because an unusual feature of many plants from this group is their dimpled lower leaf surface, where the leaf venation is thickened and raised to produce depressions between (punctate), which reflects this species botanical name. This punctation is a very noticeable feature and is what initially attracts the eye to this plant.

Besides the interesting foliage, it has bright yellow and red flowers and grows to around a metre (3’) in height. It locally favours gravel/clay soils with other heath vegetation, although further west where more common, it often grows in various sandy loams. Esperance is close to this species most easterly occurrence (the above photos taken a little to the NE of the town), with its main distribution being from Ravensthorpe to the Stirling Range and Lake Grace to Narrogin.

There is another very similar Gastrolobium (also ex Nemcia) called G. reticulatum, whose distribution overlaps with G. punctatum over much of its range; it too has a dimpled lower leaf surface. The main observable difference however is the shape of the leaf, although the leaf lengths are also noted as being distinctive, which although correct requires some clarification. G. punctatum is stated as being 8-12 mm, whilst G. reticulatum being less than 8 mm in length, however the older foliage of G. punctatum is often less than 8 mm in length too, but grows longer after flowering.

It is the leaf shape of Gastrolobium punctatum however that is consistent, which is pointed at the top, plus tapers to the petiole (stalk) with the widest portion being in the centre; G. reticulatum on the other-hand is shaped more like a arrowhead and widest at the bottom. Also the leaves are recurved away from the stem with G. punctatum, but held vertically next to the stem with G. reticulatum. In the key the G. reticulatum leaves are listed as in whorls of three, as against G. punctatum being irregularly whorled, but this is not especially the case in the Esperance region, although it may be a more reliable feature further west in their main distribution area.

The flowering period for Gastrolobium punctatum is September to October.

Gastrolobium is part of the very large and diverse Fabaceae family, but may also be listed under Papilionaceae or Leguminosae elsewhere.

Reference:

Monograph of Gastrolobium (Fabaceae: Mirbelieae)

By GT Chandler, MD Crisp, LW Cayzer and RJ Bayer

Australian Systematic Botany

Vol 15, 2002.

Gastrolobium bilobum - Heart Leaf Poison

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Gastrolobium bilobum - Heart Leaf Poison

This species is regarded as one of the most poisonous of the generally toxic Gastrolobium genus, although its brightly coloured flowers are a saving grace. It is a bushy shrub that can grow to 4 metres in height, although locally it seldom exceeds half that in size. The Heart Leaf Poison is mostly found on various loams over granite in the higher rainfall zones, however it seems very selective as to exactly where it grows and many outcrops within its preferred zone, do not include it amongst their floral accouplement.

Although many Gastrolobium species look very similar, Gastrolobium bilobum is quite distinctive by having short terminal flower clusters, plus leaves in whorls of 3 or 4 and a mostly granite habitat. The flowers are typically yellow with red markings and not predominantly orange as many species. Another feature is the red keel petals (largely hidden by the small yellow wing petals) that are lobed and have a swollen sack-like base.

The cuneate (wide top) to obovate or oval leaves are notched (bilobed and heart like) and commonly grow to 2 cm (3/4”) in length, but may be longer in the Stirling Range district. The dark green leaves are strongly reticulated (veined) and largely glabrous (without hairs), although young protected foliage can be sparsely hairy below. Despite the foliage being harmless to touch, it is nevertheless highly toxic, but the seeds are 3 or 4 times more so, so definitely not a plant to nibble.

To the east of Esperance, it can be found on many near coastal granite outcrops and as far inland as Mt. Heywood 80 km (50 miles) NE of Esperance. However, in the SW corner of the State, it is commonly recorded SW of a line between Bremer Bay and Perth. Flowering is recorded from August to December, but this would be dependent on local weather conditions, which as an example, the sparsely flowered bush above was photographed in late April.

The Gastrolobium genus is part of the Fabaceae family, but may be listed under Papilionaceae by some Authorities and older reference material.

Reference:

Monograph of Gastrolobium (Fabaceae: Mirbelieae)

Australian Systematic Botany

Vol. 15, 2002.

G.J. Chandler et. al.

Gastrolobium nutans – Box Poison

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Gastrolobium nutans – Box Poison

This species is the fourth Box Poison detailed here, the other three being G. discolor, G. melanocarpum and G. musaceum, which collectively comprise by far the majority of plants with this general appearence in the Esperance region. But alas to the casual observer all look much alike, however the latter three can be distinguished from each other by the details supplied in their individual posts.

Gastrolobium nutans on the other hand is easily separated from these similar looking local Box Poisons (within 160 km or 100 miles of Esperance), by having the leaves in threes and two ovules (seed embryos) per flower ovary. The others above have their leaves in pairs, plus 4 or more ovules, however further west there are other species with similar features, so in that area other factors need to be taken into consideration.

Locally this more distinctive Box Poison is common in an inland triangle containing mallee shrubland and heath from NW of Esperance (Rollond Road) to Ravensthorpe, then north to Southern Cross, where it grows in scattered compact colonies on sandy soils, often over gravel or rocky ground. Like most pea-flowers these plants benefit from bushfires that assist seed germination and reduce other plant competition, therefore are frequently found at their best 2-5 years after a fire event in suitable habitat.

Gastrolobium nutans has an upright habit and is recorded growing to 1.5 metres (5’) in height, although is commonly half that size. The 15-30 terminal flowers are on a short rachis (spike) 1.5-4 cm (to 13/4”) in length, the base of which is clothed in overlapping deciduous brown bracts. The leaves are to 2.5 cm (1”) in length, strongly recurved and the lower surface densely hairy, but the upper surface glabrous (without hairs), although young leaves can also be hairy on top, but these are soon lost.

The compact orange, pink and red flowers tend to bloom together between August and October to produce eye-catching displays. But despite the attractive nature of these species, they are highly toxic (although safe to handle) and from which the poison 1080 is made, so no part thereof should be consumed.

The Gastrolobium genus is part of the exceptionally diverse Fabaceae family, but may be listed under Papilionaceae or Leguminosae elsewhere.

Reference:

Monograph of Gastrolobium (Fabaceae: Mirbelieae) by Chandler, Crisp, Cayzer and Bayer. Austral.Syst.Bot. 15:661 (2002).

Gastrolobium melanocarpum - Box Poison

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Gastrolobium melanocarpum - Box Poison

Many Gastrolobium spp. are highly toxic to stock and were responsible for heavy losses in the early days of settlement. There is a group of very similar plants in the Gastrolobium parviflorum complex (also known as Box Poisons) that are reasonably common in the Esperance region, the ones so far detailed are G. discolor and G. musaceum. These are shrubs commonly around a metre/yard in height with linear foliage and terminal clusters of bright orange/red and yellow flowers.

Gastrolobium melanocarpum is restricted to the North and NW of Esperance, then further NW to Southern Cross and South to the Fitzgerald River National Park (SW of Ravensthorpe). Around Esperance it is mostly encountered on gravel soils, which may or may not have a covering of a non-calcareous sandy loam. Although it is recorded growing to 1.8 metres (6’) in height, it is usually around half this height, unless the area is heavily overgrown, thereby forcing to plant to grow taller to seek sunlight.

This species is probably the easiest to recognise as it has distinctive foliage, which is narrow (between 1-2 mm or 1/10” wide) and the edges are tightly revolute, revealing only the silky midrib on the underside. The upper surface is without persistent hairs and openly reticulated. The top of the leaves are commonly recurved, plus importantly are opposite (not in whorls of three). The flowers are usually in clusters of twenty or more and although prolific in full bloom, are smaller than the others, being slightly less than 1 cm (3/8”) diameter.

The species name of Gastrolobium melanocarpum refers to the pods that often turn black once mature. Flowering is between August to October, with September usually the most spectacular period.

Gastrolobium latifolium – Fabaceae

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Gastrolobium latifolium – Fabaceae

The genus Gastrolobium was reviewed by Chappill, Wilkins and Crisp in their Taxonomic revision of Gompholobium in 2002, in which the Brachysema genus was absorbed into Gastrolobium, however their toxicity if any are largely unknown. Gastrolobium latifolium was before that date known as Brachysema latifolium the Broad-leaved Brachysema. This is a prostrate species with large broad leaves and bright red flowers that commonly grows between Israelite Bay (east of Esperance) to Albany (west of Esperance), favouring non-calcareous soils within 50 km (30 miles) of the coast.

Like most pea-flowers, Gastrolobium latifolium does very well after bushfires or soil disturbance that removes plant competition and stimulates seed germination. Plants are at their best from 2-5 years after this trauma, but visually deteriorate to become tattered as other species around them begin to dominate available moisture and drop dead vegetation onto them. This and other stresses cause leaves to die back and spoil a once eye-catching species. Plants however are not short-lived and will persist for many years to form extensive carpets of vegetation, although these are probably made from several individuals growing together.

Generally Gastrolobium latifolium prefers the heavier loams or gravel in flat locations, often along drainage channels that are moist to wet during winter, but can be very dry during summer. Moisture availability is probably more important than sun or shade as these plants can thrive in either aspect. The flowers are bird pollinated and bloom from August to November, but being a moisture loving species will only do so if conditions are favourable, this even applies to plants in neighbouring habitats when one dries more quickly than the other.

Gastrolobium involutum – Fabaceae

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Gastrolobium involutum – Fabaceae

Like other Gastrolobium species, it is highly likely that this one also produces the poison commonly known as 1080. However, very little is known about G. involutum as it is only found near three isolated rocky outcrops in the mallee region, NE of Esperance. These seldom visited granite outcrops are Mt. Buraminya, Mt. Newmont and Mt Andrew, where the plants form reasonably compact colonies in sheltered locations that are partly shaded by trees or larger shrubs and in the deeper sandy loams (over granite) around their base.

The highly spectacular bright orange flowers are produced at the tips of new growth, which means as long as Gastrolobium involutum is growing; it is also producing flowers. Consequently this species can flower continually for several months, which it normally does from June to November, providing seasonal rainfall is reasonable.

The leaves are in pairs, soft and slender, with a longitudinal grove in the top portion. Plants commonly spread 2-3 metres (8’) and tend to grow in small thickets to 2 metres (6’) in height, but can reach 3 metres (10’) when amongst taller shrubs. Being such a colourful, nicely shaped, drought hardy and long lived shrub, it is probably a matter of time before it is grown commercially for the home garden.

Gastrolobium involutum has a Priority One Conservation Status, which is for poorly known taxa “known from one or a few (generally less than 5) populations which are under threat, either due to small population size, or being on lands under immediate threat,…..” The land is not under threat, but this species is only known from three locations and even there are not widespread and relatively small populations. There is a good possibility that Gastrolobium involutum occurs elsewhere, but this is very remote country where access is difficult, so further records are not necessarily going to turn up soon.

Gastrolobium discolor - Box Poison

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Gastrolobium discolor - Box Poison

Gastrolobium discolor is another member of the Box Poison Parvifolium Group, which superficially look very similar to each other and it was not until 2002 that they were separated into distinct species. Although several are indigenous to the Esperance region, Gastrolobium parvifolium is not one of them. Gastrolobium discolor however is one of the newly classified species and is quite common to the inland mallee region and nearby mallee habitats, ranging from the Oldfield River NW of Esperance, to Mt Ragged NE of Esperance. It favours moist heavy loams over limestone or gravel, particularly when over granite.

There are several features distinguishing this species from the others and all should be taken into account when determining identification. The most obvious difference is (as its botanical name suggests) the leaf coloration, being olive green on one side and lustrous silver on the other. The older foliage also tends to be wider, being from 5-10 mm and can be flat to curved at the edges, but not strongly recurved. The large orange standard petal is around 10 mm diameter (including the claw) and the flowers are arranged on a terminal raceme of over 25 flowers. It is most similar to G. musaceum, but this species has narrower leaves and larger but fewer flowers in its raceme.

A striking plant when in full bloom with its eye-catching orange coloration and not easily overlooked. This Box Poison can normally be found flowering from August to October, and like the others in this group contain the deadly 1080 poison to deter plant grazers, so no part should be placed in the mouth, although they are quite harmless otherwise.