The 'Bush Peas' - an introduction to the genus Pultenaea

Dorothy and Colin Woolcock

The following article is reproduced from the June 1983 issue of Australian Plants, the journal of the Australian Native Plants Society. The article was part of a longer article introducing Pultenaea and its close relatives and it was followed over the next six years by a series of articles describing the genus in detail (see "Further Information").



Introduction

   Pultenaea villosa
   Pultenaea villosa
Photo: Brian Walters

Endemic in Australia, the interesting and complex Pultenaea group (about 120 species) is the largest genus of our native pea-flowers. Occurring in the temperate areas of all States, except the Northern Territory, it is widely distributed and frequently very common, with over 50 species found in New South Wales, almost as many in Victoria, 20-30 in both Western Australia and South Australia, and 10-20 in Tasmania and south-east Queensland. Some of these are very localised, and restricted to a small area of specialised habitat; others range through several states, producing massed displays of great charm and colour. frequently along roadside verges

Within their chosen habitats the bush-peas may be found in alpine and sub-alpine regions (particularly near swamps and bogs), in well-drained, montane forests, along the tablelands and in coastal woodlands, plains and heathlands -- in good rainfall localities. A few species only will tolerate the low to moderate rainfall of mallee-type country and there they seek out the relatively damp depressions and soakage areas.

In this diverse group, which is also part of a very large botanical family, a few Pultenaea species tend to merge, in appearance, into closely related genera; but the great majority have a distinctive character and can be readily identified as belonging to this genus. The final identification of the individual species often depends on quite small changes in feature and structure.

As the popular name "bush-peas" suggests, most Pultenaea species are upright, often bushy shrubs, sometimes growing several metres tall, but frequently smaller, averaging between 0.5-2 m high. A few are either prostrate or procumbent, and the swamp species tend to be rather weak undershrubs, using neighbouring plants as support. Flowering time is usually from late winter through spring to early summer, though those from higher and wetter areas may be later still. Generally, but with a few exceptions, the flowers are yellow to orange in colour, marked or suffused with red, particularly the keel and the outside of the standard. The colour glow of a hillside or a gully of Pultenaea in full flower can be quite breathtaking.

Characteristics

Along with a number of other important genera, the Pultenaea genus is classed in the Mirbelieae tribe, in which the distinguishing factor is the stamen arrangement. Some of the related Mirbelieae genera (Phyllota, Dillwynia, Latrobea, Eutaxia, Aotus, Podolobium, Oxylobium and Gastrolobium), have characteristics which may fit a number of the following requisites but not all.

Pea flower diagram   

Stamens: Perhaps the first examination made in identifying any native pea-flower is to open gently the keel of a flower and check the stamen setting, preferably with a hand lens. All Mirbelieae, including Pultenaea, will have 10 stamens or filaments which are individually free to their base.

Stipules: These are defined as appendages growing in pairs at the base of leaf-stems adjacent to branchlet-stems. They vary in length from less than 1mm to 4-6 mm or even larger. Rarely, they are absent. The presence of stipules is not confined to Pultenaea, so that additional features are necessary to confirm the plant as a bush-pea. However, many Pultenaea species have prominent stipules, which impart a characteristic appearance readily recognised.

Bracteoles: These are bracts, usually in pairs, defined as occurring either on the flower stalk or the calyx-tube itself. Bracteoles may occur in genera other than Pultenaea, but their presence and appearance are helpful in establishing identity, as they are attached either at the calyx-tube base or on the tube itself. They vary in size, shape, complexity and attachment and can be simple, bilobed or trilobed. A hand lens is again recommended to check these details. Only rarely are bracteoles not present, although in some species they may be enclosed in additional (floral) bracts, which require careful removal. The presence of both leaf stipules and calyx bracteoles will establish the Pultenaea identity in many instances.

Seed Pods - Fruits: As shown in the diagram, the pod is ovate, not large, but larger than the calyx, and may be flat or swollen, with never more than 2 seeds. These pods open readily on maturing (dehiscent) and expel the seeds, so that one may find only empty pods if arriving too late. The individual seeds have a creamy-white growth, known as an aril, which is present on all Pultenaea seeds but not on those of some related genera.

Leaves: These may vary considerably in size and shape, are alternate, opposite or in whorls, but are invariably simple. If a plant has trifoliolate leaves (as in clovers, Glycine, Kennedia and others) or pinnate leaves (as in Swainsona, Indigofera) it cannot be a Pultenaea species.

Inflorescence: Flowers are in umbel-like heads, in axils of leaves clustered near ends of branchlets, axillary or solitary, never in extended racemes.


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