Carnivorous Plant Encounter, Walpole, WA

Originally appeared in Flytrap News 10(4): 8-12, (1997)

Carnivorous Plant Encounter, Walpole, Western Australia

Robert Gibson

In late December 1996 I spent 3 days traveling around the south coast of Western Australia, observing 15 species of carnivorous plants in the wild whilst bushwalking. The plants seen, around Nannup, Northcliffe and Walpole, included many I have found elsewhere on the south coast as well as a few surprises; including Drosera binata, D. hamiltonii and Utricularia simplex. Following is account of the carnivorous plants encountered.

Cephalotus follicularis

The Albany Pitcher Plant was seen at two sedge swamps either side of Walpole. A third location, near Pemberton, was visited but was too overgrown to be deemed safe for exploration. At the sedge swamp west of Walpole the pitcher plants grew on the upper slope of the swamp, often at the foot, or the pedestals, of a distinctive, and robust species of Gahnia “grass”. This sedge has grey green leaves with coarsely serrated margins and smooth scapes, to 2.5m tall with flowers enclosed by a pair of large bracts. The height of vegetation in this swamp, which included many species of Myrtaceae, varied from 0.8 to 3m, and it appeared to have been burnt in the last few years.

Clumps of Cephalotus varied in appearance from fully green, with an equal production of pitchers and non-carnivorous leaves, to striking clumps of pitchers, to 5 cm tall, with abundant red pigmentation on the interior and exterior of the pitchers, in which the translucent “windows” on the lids appeared as vibrant white stripes. The contents of one pitcher examined consisted primarily of the recognisable remains of dark brown ants, to 6mm long, a species which lives in the sedge swamps. The remains of scapes were found of some clumps indicating flowering the previous summer.

At this site, in damp peaty soil, Cephalotus grew in the company non-flowering Drosera hamiltonii, D. binata and D. pallida. It was interesting that no pygmy Drosera nor Utricularia grew in this section of the swamp.

The second site, consisted of carbonaceous shale and sandstone cliffs at the back of a narrow beach, over which fresh water was constantly seeping. The pitcher plants grew on unstable slopes, the surface 30cm of which periodically slipped downslope leading to the death of all plants on board through desiccation or immersion in salt water. Many of the pitcher plants here were in scape, which grew to 60cm tall and varied in the level of flower development, although no flowers were open at the time. A well-formed rosette of non-carnivorous leaves precedes the emergence of a scape at a growing point.

The pitchers grew to 3cm tall and were generally brightly red pigmented in response to exposure to the sun. The contents of one old pitcher examined proved to be a soup of unrecognizable invertebrate body parts as well as 3 white, very healthy, living, worm-like dipteran larvae. The only variation observed in the plants at this site was the presence or absence of stipules on the lower third of the scape. At this coastal siteCephalotus grew with pink petalled plants of Drosera pulchella.

Drosera binata

Drosera binata was found on the edge of a sedge swamp near Broke Inlet, west of Walpole, growing with Cephalotus follicularis, D. hamiltonii and D. pallida. The plants had one to five olive green, erect, self-supporting petioles to 20cm tall and supported a singly forked lamina to 6 cm long. The lamina, with fully dark red retentive glands, captured small flies and midges and were projecting through into small openings amongst sedge and restio leaves. No plants were in scape or flower, but it appeared that the plants were reproducing asexually from the thick root system.

This species appears to be native to the area, it is neither dominant nor rare, and appears to be significantly far from major human disturbance and weeds. Given this species’ intolerance of submersion and prolonged desiccation only a few habitats appear suitable for it on the south coast of Western Australia. It grows in sandy peat, at the sloping edge of a sedge swamp, where it drains a low wooded ridge. At the time of my visit a thin dry crust had formed over the moist sandy peat in which the plants grew.

The presence of Drosera binata on the south coast is food for thought. Is it a relict form of the species which has subsequently spread east and prospered and diversified in areas of year-round humidity? The form of this species is very like the “t-form” which grows in Tasmania, and it would be interesting to see the flower and seed morphology of this Western Australian population in the first summer following the next bushfire in the swamp. It may be no coincidence that it grows with Cephalotus follicularis and Drosera hamiltonii, two taxonomically isolated and relict species.

D. dichrosepala

A small colony of D. dichrosepala was found beside a small creek near Northcliffe. The green open, semi erect rosettes, to 1.3cm diameter, grew in fine-grained white quartz sand in a small clearing in Jarrah woodland. Several plants had conspicuously hairless scapes developed, a few with small white petalled flowers open in the late afternoon. In this area the introduced Watsonia bulbillifera was becoming established and may out compete this, and the majority of small native plants.

D. hamiltonii

Three colonies of the attractive D. hamiltonii were seen on this visit. The first was on the edge of a drainage channel through a sedge swamp near Northcliffe. Vivid red rosettes, to 8cm diameter were seen in exposed areas, one of which had an erect scape, to 60 cm tall with 19 flowers, the second last of which had recently closed. More abundant, smaller, less intensely pigmented rosettes grew nearby, shaded by clumps of sedges and an array of fallen leaves. Several plants were wilting in response to drying soil, and would likely die down to the thick rootstock from which new rosettes would likely later sprout. Pink petalled plants of Drosera pulchella grew nearby, on disturbed soil at the roadside, and the bottom of the drainage channel was locally brightened by purple flowers of Utricularia dichotoma.

The two other sites were in coastal plain swamps west of Walpole. One site, with three plants with open pink flowers, was in disturbed swamp, where 30 rosettes, to 6cm across, nestled at the foot of a small manmade scape of peat beside a drainage pond. The plants grew in moist, but not sodden peaty sand, in a highly exposed area. They caught a few small flying insects and the dead leaves of small leaved shrubs of theMyrtaceae family. As with the above site the plants in the most open locations flower, perhaps as a response to the enhanced opportunity  for seedling establishment? Around these plants grew D. pulchella, D. roseana, D. menziesii ssp menziesii and U. multifida.

At the D. binata and Cephalotus swamp grew abundant rosettes of D. hamiltonii. Unlike the above sites  the rosettes were scattered and variably shaded and hidden by a well developed overstory of sedges, restios and shrubs. No plants were in flower and the rosettes were generally 3 to 6 cm across.

D. menziesii ssp menziesii

Dieing scrambling stems of D. menziesii ssp menziesii were found in two habitats – in coastal plain swamplands and in thin, moss-covered soil of granite outcrops in Jarrah and Karri forest; habitats with seasonally extreme changes in soil moisture levels. The stems grew to 30cm tall, many of which had the remains of inflorescences. In rare cases some leaves were still alive and bedewed. In the coastal plain swamps this species grew with D. pulchella, sometimes with D. roseana, D. pallida and D. stolonifera ssp compacta and U. multifida. On the granite outcrops it often grew with U. multifida.

D. neesii ssp neesii

Rare plants of D. neessi ssp neesii were found in recently burnt coastal plain north of Windy Harbour. The plants grew to 15 cm tall,  were shedding seed and were all but fully dormant. The plants grew in the company of D. pulchella in dry surfaced peaty sand.

D. occidentalis ssp australis

Scattered plants of diminutive rosettes, to 1cm across, with round red lamina on thin petioles, were found in coastal plain swamps and lake margins between Windy Harbour and Walpole. Solitary flowered short scapes, to 2cm tall were seen on a few plants but no open flowers were seen which may have revealed that some of the plants could have instead been the very similar D. pygmaea.

D. pallida/ D. erythrogyna

Dieing scrambling, non-flowering stems of either D. pallida or D. erythrogyna, or perhaps both were found in a few sedge swamps between Northcliffe and Walpole. Plants were found in the company of Cephalotus follicularis and D. hamiltonii, which had lamina with fully circular outline, which indicates they may be D. pallida. The plants were almost fully dormant and few were still bedewed.

D. platystigma

Golden green rosettes, to 2 cm diameter of Drosera platystigma were found growing in disturbed moist sandy soil beside the road south of Nannup. Initially I thought I had found a colony of D. pulchella on account of the wide petiole and rounded lamina of the flat rosettes. Many plants were in scape, three of which were found to have open flowers during my mid-morning visit. The orange petalled flowers were 6mm across, each petal had a dark orange base from which extended a few veins into the bulk of the petal; and are very like the form illustrated in Kondo and Kondo (1983) on page 61. It was not until I examined the structure of the dark orange styles that I recognized this species

D. pulchella

Abundant golden green rosettes of D. pulchella were seen in most damp locations between Northcliffe and Albany. Two forms of the species were seen, those with pink petals; which appear to be the most widespread pygmy Drosera in Western Australia, and those with orange petals. It has been suggested that the pink petal form is more common in the lower lying ground whilst the orange-petalled form favours higher ground, often in laterite-derived soils. My observations were contrary to these but this may reflect mixing of the forms due to human disturbance of the land.

D. roseana

Attractive, semi-erect rosettes of D. roseana were found in coastal plain swamps between Northcliffe and Walpole, often in the company of D. pulchella, D. occidentalis ssp australis/ D. pygmaea and U. simplex. Plants, to 1.8 cm diameter, had elongated red lamina on narrow green petioles, were in scape, with many small white petalled flowers open at the time of my visit, although the flowers were observed to open primarily under sunny conditions. The distinctly hairy scapes and sepals are characteristic of this species.

D. stolonifera ssp compacta

A single colony of D. stolonifera ssp compacta was found in a sedge swamp east of Northcliffe. The stems, to 12 cm tall, were pale brown and almost fully withered but still bore the large, paddle shaped leaves born in whorls. No sign of scapes were seen.

Utricularia dichotoma

Attractive flowering clumps of U. dichotoma were seen beside creeks and in drains in Jarrah woodland near Northcliffe. The plants had scapes to 20cm tall bearing a pair of opposite flowers. The flowers had triangular lower lips, to 1.3 cm across by 1 cm long, the free rounded corners of which were curved gently down. The palate consisted of two raised yellow ribs edged by dark purple, and is partially overhung by the wedge-shaped upper lip. The lower lip was lilac in colour save for one small colony where it was same very pale purple of the upper lip in all plants seen. This bicoloured form of the species is most attractive. The spoon shaped dark green leaves often grew under a film of algae-stained water.

This highly localized species grew near Drosera pulchella and D. hamiltoniiand is also known from south eastern Australia.

U. simplex

Diminutive clumps of U. simplex were seen in coastal plain near Windy Harbour, and were recognized initially from the comparatively large open flower on a few scapes. The purple flowers have a bluntly triangular lower lip, from under which the end of the horizontal spur projects. A vertical wedge-shaped lower lip rises above the palate of the lower lip which is marked by a touch of pale yellow pigmentation. The solitary flowers, to 6mm across and high, are held on the end of dark purple scapes, to 3cm tall. The narrow dark green linear leaves, to 4mm long by 0.7 mm wide, are often hidden by fallen leaves and algae.

This species grew in moist peaty sand in the company of D. pulchella, D. occidentalis ssp australis/ D. pygmaea and D. roseana, and is closely related to U. lateriflora and U. delicatula which are native to south eastern Australia and New Zealand respectively (Taylor, 1989).

U. multifida

Bright pink flowers of the widespread and delightful U. multifida were seen in roadside gutters, coastal plain swamps and on granite outcrops from Northcliffe to Denmark. Whilst the peak flowering period had finished, and many flowers had now withered and the fine seed shed, many plants in the colonies had produced a second or third scape which were still growing into early summer. The scapes, to 15cm tall, had up to 7 flowers. These supported attractive clear pink, or white in one location, with a three lobed lower lip and bifurcated upper lip with a palate of three to five sulphur yellow ridges in between. One aphid attacked plant had an unusual double flower in which the two incomplete flowers were joined along a line down the centre. This bladderwort was frequently found in the company of D. pulchella.

This section of the coastline is dominated by kwongan (“heath”) covered coastal plains with lakes, swamps and few sizable perennial streams. The undulating hinterland consists of low granitic outcrops, with a variable amount of the laterite (a weathering product) preserved; and upon which the magnificent Jarrah and Karri forests grow. A few scattered granitic, forest clad hills occur close to the coast where they occur as vegetation islands surrounded by extensive swampy coastal plain. The geomorphology of the coast suggests that the sluggish streams, and all but the large rivulets, have been dammed by extensive coastal sand dunes at the backs of beaches. Sand, peat and clay accumulate in the basins behind the dunes whilst the water seeps through to the ocean. Under the present climate, with winter maximum rainfall, and summer drought, soil on granite and laterite outcrops and a large area of the coastal plain vary enormously in water content throughout the year. Only the soil in the center of the larger swamps, beds of the larger streams, and any larger lakes remain wet all year round. With the large variation in habitats, soil types and seasonal water table levels it is perhaps not surprising that so many species have evolved in the south west of Western Australia.

When walking through the swamps it is apparent that it is home to many animal species as well. The most conspicuous are the invertebrates, of which flies, mosquitoes, other Dipterans, ants and spiders are the most frequently encountered. Along the south coast of Western Australia are species of black, moderately ornamented colonial spiders which spin strong but not sticky webs between the majority of shrubs and tall herbs. Snakes are common residents of sedge swamps too, many species of which are venomous. When venturing into such habitats I recommend wearing long trousers, sturdy shoes, a hat and either a long sleeved or short sleeved shirt. The spiders are harmless but few people are comfortable with them and their webs over their skin. As for the snakes; they generally keep out of your way so make lots of noise, move slowly and watch where you put your feet. Remember that we are guests in these environments.

The few days spent traveling leisurely around this section of the Western Australian south coast were very enjoyable, relaxing and rewarding. It was a pleasure to get a feel for the nature of this section of the coast and how a selection of carnivorous flora fits in there. The observations have been sumptuous food for thought particularly about the history and ecology of apparently ancient species such as Cephalotus follicularis, Drosera hamiltonii and D. binata.

REFERENCES

Kondo and Kondo, 1983. Carnivorous Plants of  the World in Colour. Ienohikari Association, Tokyo.

Taylor, P. 1989. The Genus Utricularia: A Taxonomic Monograph. Her Majesty’s Stationery Office, London.

Posted in Field Studies