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 travelling 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 unrecognisable 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 site Cephalotus
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 the Myrtaceae 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 recognised 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 localised species grew near Drosera
pulchella and D. hamiltonii and
is also known from south eastern Australia.
U. simplex
Diminutive
clumps of U. simplex were seen in
coastal plain near Windy Harbour, and were recognised 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 sizeable 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 centres 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 sleaved 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 travelling 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.
