Pea-flowered plants are legumes and belong to family Fabaceae, which is the third largest in the plant kingdom after the orchid and daisy families. Most leguminous plants develop root nodules in association with Rhizobium bacteria and are capable of converting atmospheric nitrogen into more complex nigrogenous compounds. The wattles (Acacia) and the sennas (Senna) and their relatives are also legumes.
Environmental needs of native pea-flowering plants are complex, and on-going study will shed further light on the specialised needs of various species. A brief and simple description of the structure of pea flowers can be viewed here.
Oxylobium ilicfolium - Native Holly or Prickly Shaggy-pea has particularly attractive 'holly-shaped' foliage and neat growth habit. This plant is reasonably common on poor soil in small pockets of unmaintained scrub and roadsides. Flowering season is September to November. More details at PlantNET.
The pea flowers generally consist of understory shrubs, herbs and trailing plants in a range of habitats. Habitat loss as a result of urban and rural development is a major threat to the survival of native plant communities in the Hunter Valley.
Other threats include weed invasion, nutrient enrichment of soil due to agriculture and fertilisation practices, disturbance by vehicles and rubbish, along with failure to implement appropriate fire regime required by some species.
Roughly half of the Fabaceae genera are predominately fire sensitive (eg. Dillwynia, Pultenaea) with the remainder able to resprout following fire (eg. Daviesia, Bossiaea).
Indigofera australis - Native Indigo is also an often seen roadside plant with showy pink to lilac racemes sprouting from leaf axil. It is a spindly bush to a metre or more in height that sways in the breeze, and flowers from August to September. More details at PlantNET.
Some legume species have a release mechanism which ejects seed from mature pods a small distance from the plant (eg. Daviesia, Kennedia, Hardenbergia), while other species have a passive release mechanism whereby seeds are dropped directly to the ground.
Fabaceae generally have hard seeds that dry out during ripening and become impermeable to water. Most have long-lived seedbanks stored in the substrate. Some seed dormancy can only be broken by fire, which creates restrictions on germination due to the inappropriate implementation of fire regime locally. Here is some interesting and easy-to-read observations regarding fire and Australian natural environments. There is more here.
Not only do many legume species rely on heat and/or smoke from fire to break seed dormancy, but many plants do not reach sexual maturity until between three and five years, therefore, if fire occurs too frequently, plants do not have the opportunity to produce seed.
Jacksonia scorparia - Dogwood makes an attractive display of weeping yellow, leaf-less shrubs up to two or three metres high, in October and November. If you are lucky enough to see them massed, they are beautiful. They often grow where run-off water occasionally collects. More details at PlantNET.
Numerous insects are associated with legumes during flowering and fruiting. Pollinators include native and introduced bees, wasps, beetles and flies. Certain beetle seed predators appear to be totally dependant on legumes for their survival. Ants are thought to be important distributors of seed amongst the peas.
Kennedia rubicunda - Dusky Coral-pea is a robust climber and I was pleasantly surprised to find this plant with large red pea flowers scrambling over shrubs, weeds and rocks. The 4cm-long flowers hang in an eye-catching display. As with all Kennedia species, leaves are arranged in threes. Its main flowering period is between July and November. More details at PlantNET.
Daviesia ulicifolia - Gorse Bitter-pea. Although the yellow and brown flowers on this low rounded shrub are small, I found it an interesting plant with its small rigid sharply-pointed leaves. It flowers from August to November and has several subspecies. More details at PlantNET.
Many of Australia's native plants have prickly foliage. Presumably this protects young plants from being grazed by native animals. During my bushland rambles, I have noticed that peas are no exception to sharp and stiff leaves. I find these to be some of the most interesting plants I encounter.
PlantNet has a comprehensive list of Australian pea-flowering plants with information and photographs.
Hardenbergia violacea - Purple Twining-pea is a common and vigorous ground-cover that trails through the undergrowth, over rocks and roadside banks. This plant has been adapted well to home garden use. It has broadly ovate strongly veined leaves up to 9cm long and conspicuous racemes of violet flowers with yellow centres. Flowering period is mainly July to October. More details at PlantNET.
So keep a look out for these little beauties of the Australian bush blooming in a rainbow of colours from late winter to early summer. This is just a small sample of what's on offer for those nature observers with a keen eye. They are fascinating plants with complex lives and interesting habits. They can also be very pretty. Enjoy them!