Description, Distribution, Ecology and Cultivation
Keywords: chemistry: habitat
--- cultivation: Aldrovanda --- ecology: Aldrovanda.
This plant was first cited
as Lenticula palustris Indica in 1696 by Plukenet. In 1747 Monti
described and named it Aldrovandia in honor of the Italian naturalist
Ulisse Aldrovandi (1522-1605). Finally in 1753 Linnaeus took over Monti's
description and in his Species Plantarum used the name Aldrovanda vesiculosa,
which has been noted as being an orthographic error (Duval-Jouve, 1861),
although the original spelling is to be retained. Since the last part
of the 19th century Aldrovanda has been studied extensively. It
is commonly known as the Waterwheel Plant.
The genus Aldrovanda
is monotypic nowadays, but it probably contained more species in the past
(Huber, 1961; Degreef, 1997). The Waterwheel Plant belongs to the family
Droseraceae. As an aquatic, it is clearly separated from the rest of the
The rootless plant floats just
below the water surface (Figure 1). The measurements of different parts
of the plant body are rather variable. The length of adult plants ranges
between (1.5)6--11(20) cm with a shoot diameter 1 to 2 cm (Aston, 1983).
The serrulate stems are 0.6--0.7 mm wide and basically simple (Caspary,
1859). In plants growing under favourable conditions, the main shoots
usually branch after every 3--4 cm (5--7 whorls) giving rise to short
lateral branches in the axils of whorls. In time these branches may form
offshoots. In temperate regions, where Aldrovanda rarely flowers
(bearing only abortive or no seeds), this is the only way of reproduction.
In average 12 to 19 whorls are arranged along the stem (Kaminski, 1987a)
like spokes in a wheel and each whorl consists of (5)7--8(9) leaves 7--11
mm long (Caspary, 1859). The distance between grown-up whorls ranges between
0.5 to 0.7 cm (Kaminski, 1987a). When in growth new whorls are formed
at the plant's apex, while the oldest whorls and internodes at the rear
die (Ashida, 1934). The rate of stem elongation of plants in Japan has
been found to be 0.4--0.9 cm/day (Komiya, 1966). This fast growth is unrivaled
among terrestrial carnivores, none of which produces a new rosette or
even a new leaf every day!
The leaf consists of a dorsally
flattened petiole, 5--6(9) mm long (Caspary, 1859), connate at the base,
broadened upwards and ending in a trap and (1)4--6 pointed bristles, each
6--8 mm long (Diels, 1906), arranged laterally and dorsally to the trap.
The bristles protect the traps from being unintentionally closed by floating
debris. The petiole is important for the plant's photosynthesis and contains
air chambers which contribute to helping the plant float.
The Waterwheel Plant has the
same trap mechanism as Dionaea muscipula, but the traps are smaller
and function under water (Iijima, 1981). Darwin named it "the miniature
aquatic Dionaea" (Darwin, 1896). The trap closes with amazing
rate within 0.01--0.02 seconds (Ashida, 1934, 1935). This is one of the
most rapid movements found in plants. The details of how the trap closes
are still rather obscure.
The traps have a leaf-blade
consisting of two semicircular lobes, convex outwards, each 4--5 mm wide
and 5--7 mm long and connected along the midrib. The trap stalk is twisted
90° to the left. This way, one lobe is turned to the bristles and
is called the bristle-side lobe. The other lobe looks away from the bristles
and is called the free-side lobe (Ashida, 1934). In addition to this torsion,
the trap is bent backwards through an angle of 30-40°. These torsions
are of an evolutionary importance because the chance of catching prey
is enhanced when the mouths of the traps face outwards from the stem (Lloyd,
1942). When the trap closes, the free-side lobe bends to a greater extent
than the opposite lobe. This explains the asymmetrical shape of the closed
trap (Ashida, 1934).
Each lobe consists of two regions,
a thin two layered marginal and thicker three layered central one. Note
how delicate the lobes are! The border line between the two regions is
called the enclosure boundary (Ashida, 1934). The margin of each lobe
is bent inwards and carries 60--80 small teeth (Fenner, 1904). Trigger
hairs are found in the central zone. They are 0.5--1.5 mm long, 0.05 mm
wide (Lloyd, 1942), 30--40 in number, of which 18--20 are near the midrib
and 7--9 are near the enclosure boundary (Haberlandt, 1906).
In temperate regions the plants
survive winter by means of elliptic turions (with acute poles) about 4--6
mm long. Under ideal conditions these sink to the bottom of the lake and
start floating again as they start to grow next spring. In tropical regions
the plant grows throughout the year without forming turions. The plants
flower and set seed towards the end of summer only in warmer climates
where water temperature are higher than 25°C (77°F). The small
solitary 8 mm flower (Lloyd, 1942) arises above the water surface, carried
by a short 5--15 mm (Aston, 1983) robust peduncle emerging from a whorl
axil (Figure 2, front cover). The capsule becomes pendulous after flowering.
The flower has a strict pentamerous
structure with five sepals, white or tinged pink petals, stamina and styles.
The ovary is unilocular, superior, subglobulose, with 4 or (usually) 5
placentas bearing 8--13 ovula. The placentation is parietal. The capsule
is globulose, membranous, 4 mm long, 3 mm wide, and up to 1.5 times the
length of the sepals (Aston, 1983). Seeds number mostly 6--8 per capsule
or rarely fewer (Diels 1906), are broadly ellipsoidal with a short thick
basal foot, are operculate, black, shiny and measure 1.5 X 1 mm (Diels,
1906). The pollen grains are 45--63 m
m MICRONS large, and are united in tetrads. Each grain has 3 pores with
an operculum (Takahashi & Sohma, 1982).
(Focusing on Europe)
is distributed widely. It grows in Africa, Asia, Australia and Europe
but is absent from North and South America (Caspary, 1859; Berta, 1961;
Jäger, 1964) and Antarctica. The species has its most northern distribution
in Europe. With its sophisticated mobile traps, one might think that Aldrovanda
would be at the top of the evolutionary ladder and therefore of recent
origin. But this is not so. The morphology of the flower and the age of
fossil seeds and pollen (Huber, 1961; Degreef, 1997) are indications of
the archaic character of the plant.
The oldest traces of the Waterwheel
Plant in Europe are seeds and pollen from the Upper Cretaceous (85--75
MYA) and Eocene (55--38 MYA), respectively (Knobloch & Mai, 1991;
Huber, 1961). The warm Tertiary climate was favourable for a wide distribution
of the plant. Later, during the glaciations of the Quaternary; Aldrovanda
was regularly driven back to southern Europe (Berta, 1961). More about
the fossil record of Aldrovanda in another article in this volume
(Degreef, 1997). The question of the origin of modern Waterwheel Plants
in Europe is still unsolved. Two theories have been formulated. According
to some authors the plant is a relict of the Tertiary flora (e.g. Berta,
1961). They assume that the plant never disappeared completely from the
continent. This theory is supported by numerous fossil records, the fragmented
distribution of today and the fact that Aldrovanda forms turions
which might be an evolutive adaptation for plants in temperate regions.
Jäger (1964) states that the modern plants were introduced by migratory
birds coming from the tropics (see below). This theory is partly supported
by the plant's absence in North and South America and the fact that there
is no longer a species diversification. We do not know which theory is
correct. A study of growth behaviour of African plants grown in temperate
Europe (i.e. do they form turions?) and investigation of the genetical
differences between European and African plants would help to solve the
mystery (Studnicka, 1984). Unfortunately, there are no records of recent
observations in Africa.
Today, Aldrovanda is
dispersed irregularly and sparsely over a large part of central and eastern
Europe (Berta, 1961; Jäger, 1964).
Looking at a distribution map
indicating all 19th and 20th century sites (Berta, 1961), we see that
the northernmost distribution in western Europe was situated in southern
France whereas in eastern Europe it was much more to the north, in the
neighbourhood of St. Petersburg in Russia. (60.5 parallel). Apparently
the winter temperatures are not so determinative for its distribution.
This a bit strange for a plant which is known as loving a warm climate.
And why is the species absent in the northwest Europe with its milder
winters? The point is that it is not the winter but the summer which determines
where Aldrovanda grows or not. If the water temperature during
the growing season is sufficiently high, then the plants survive. This
explains why the species does not grow in northwest Europe with its mild
summers, but on the other hand does grow in northeast Europe with its
warmer continental summers.
Discoveries of the Waterwheel
Plant were published in the literature from the 18th and especially from
the 19th century on. That time the plant was found in many countries:
France, Switzerland, Germany, Poland, Czechoslovakia, Austria, Hungary,
Romania, Belarus, Baltic, Ukraine, Russia, Italy, Yugoslavia, and Bulgaria
(Caspary 1859). It can be assumed that the influence of human activities
on the distribution of Aldrovanda was not substantial before 1940.
Today Aldrovanda occurs
in Hungary, Italy(?), Poland, Romania, Switzerland (where it is introduced)
and the countries now called Yugoslavia, Ukraine and Russia. The serious
decline of the species during this century is most likely caused by the
destruction and disturbance of its sites by man (water drainage, pollution
by agriculture and industry, and disturbance by recreation). As the plant's
ecological requirements are very strict, it is very sensitive and is one
of the first plants to disappear. This extreme sensitivity is to be expected
for a plant at the edge of its distribution.
In western Europe the decline
is spectacular and the plant is almost extinct. But it must be stressed
that the number of sites there was smaller than those in eastern Europe.
The plant still grows in eastern Europe. Here too the disappearance is
alarming, but less striking because of the higher number of sites. The
expected future agricultural, touristic and industrial development in
that part of the continent will not bring much good for Aldrovanda.
How does Aldrovanda
spread to other places? Most likely this happens via turions or whole
plants. In (sub-) tropical areas, seeds might get dispersed too. Three
likely dispersal agents are described below.
According to Jäger (1964)
birds play an important role in the distribution of the plant. A turion,
seed, or less likely a whole plant may get stuck to a bird's legs or feathers
and thus be carried to another place. Theoretically, a seed could, once
eaten, land somewhere else via the excrements of the bird. This is speculative
as we do not know whether these minute seeds are eaten and whether the
viability is still intact after passing through the intestines of the
bird. The occurence in mountainous regions is most likely a result of
introduction by birds. The similarity between the worldwide distribution
of Aldrovanda and the routes of some migratory birds is remarkable
(Jäger, 1964; Studnicka, 1984). So birds might play a role for long
distance transport between continents as well as for short distance spread.
In regions with interconnected
habitats, the plant can be brought to another place by the natural flow
in the canals and streams.
Habitual floodings in floodplain
areas might transport Aldrovanda to isolated pools.
It is likely that the plant
will disappear from Europe in the future. To prevent it from vanishing,
the sites must be protected. Protection alone will not preserve Aldrovanda
from extinction, because most disturbance is caused by factors coming
from outside the habitats. Despite a number of possible threats, the exact
reasons for vanishing are often unknown.
(Re-)Introduction might help
to maintain the species. To be successful the knowledge of Aldrovanda's
ecological requirements must be completed first. Suitable alternative
sites are becoming very rare these days.
To prevent further genetic
impoverishment, there is an urgent need for a gene stock of plants of
different origins. Suitable methods for stockage are tissue culture and
cryopreservation. Propagation methods (in vitro and in vivo) need to be
optimized so that natural populations can be left undisturbed and only
propagated specimens should be used for all kinds of experiments.
Being ousted by competing species,
Aldrovanda has to move regularly to survive. The shorter the travelling
distances, the greater the chance of survival. Aldrovanda is able
to survive for a long time only in areas with enough suitable habitats
close to each other.
Aldrovanda has a weak
competition ability with surrounding plants. Space, nutrients and light
are in limited supply. The only way to withstand elimination is a vigorous
growth and propagation. These are promoted by a number of factors, discussed
As a free floating aquatic,
Aldrovanda grows in pools, lakes and river deltas at places with
standing water (Berta, 1961). Typically it is found near the shore, loosely
surrounded by other plants (Figure 3). This very productive zone is characterized
by rapid succession among different plant populations. So soon Aldrovanda's
place will be taken by others and the species will have to migrate to
The plant prefers shallow water
less than 1 m deep. As the plant is very susceptible to dessication, a
permanent water level is essential throughout the growing season. Most
of the time the bottom of the stands is covered with a thick layer of
partly decomposed plant remains. In temperate regions the water surface
might freeze in winter. The shallower the water, the higher the risk the
turions will be killed by the ice. So it may be advantagous for turions
to overwinter at places with a considerable water depth (Kaminski 1987b).
The water in Aldrovanda
stands is mesotrophic and thus medium-rich in nutrients. In oligotrophic
waters the plant is always absent. Eutrophication of the water (by intensive
agriculture) is thought to be one of the major reasons for the disappearance
of the plant. The pH of natural waters ranges between 5.6 and 6.8 (Komiya,
1966; Kaminski, 1987a).
The analysis of the water in
Polish sites yielded the following results: 0.3--0.6 mg/l N-NO3,
1.0--1.5 mg/l N-NH4, about 0.06 mg/l P-PO4, 2.4--4.0
mg/l K, less than 40 mg/l Ca, 6.0--15.0 mg/l Mg, 8.0--13.0 mg/l Na, 0.5--1.0
mg/l Fe, 25 mg/l SO4, 5.0--12.0 mg/l Cl and 3--5 mg/l of organic
carbon (Kaminski, 1987a).
The decomposition of plant
material results in the production of organic humic acids. Their concentration
in Aldrovanda stands is medium (3--5 mg/l). Waters like these are
called dystrophic. Typically, high concentrations of humic acids are found
in lakes with a thick layer of plant residues at the bottom. The humic
acids are important for Aldrovanda. They are responsible for a
much better plant growth during the growing season and they seem to regulate
the sinking of the turions (Kaminski 1987b).
Carbon dioxide is the carbon
source for photosynthesis allowing a plant to grow. Aldrovanda
needs relatively high concentrations of CO2 (0.5--2 mM) (Adamec,
1994). One of the main sources of carbon dioxide is the thick organic
layer at the lake bottom, where it results from the decomposition of the
organic material. So it is advantageous for Aldrovanda to float
near this source in shallow water. Phytoplankton, filamentous algae and
other aquatic plants can deplete the CO2
During the growing season Aldrovanda
needs relatively warm water: at least 16°C (61°F), ideally 23--30°C
(74--86°F) (Saito, 1972; Haldi, 1974; Mazrimas, 1978). The water
warms up most rapidly at places with low water depth (typically near the
shore), dark coloured bottom and full sun.
The turions sink to the bottom
of the lake in autumn where they overwinter, being protected from the
surface frost by the insulating ice above them. Under less favourable
conditions the turions fail to sink (Schoenefeld, 1860).
Aldrovanda prefers places
with high irradiance (Saito, 1972; Haldi, 1974; Hanabusa, 1974). Light
is needed for photosynthesis and warms the water. Several factors influence
the availibility of light to the plant. First of all, the vegetation above
the water surface, which should not be too close, too dense or too high,
can block light. Floating and submerged plants can intercept light too,
so the Waterwheel Plant prefers loose plant communities with nearby open
water (Figure 4, back cover). Another factor is the transparency of the
water. Suspended matter, algae and/or phytoplankton can make the water
less transparent and thus reduce the amount of light for Aldrovanda.
The Waterwheel Plant is very susceptible to overgrowing by filamentous
algae (Saito, 1972; Haldi, 1974).
Quite a number of other macrophytes
can be found near Aldrovanda, indicating its rather large phytosociological
range (Figure 5). European populations belong to the floristic unions
Nymphaeion, Phragmition and Magnocaricion (Caspary, 1859; Berta, 1961;
Kaminski, 1987a). Plants secrete chemical substances which can influence
the growth of other plants. The influence can be positive or negative.
It has been confirmed experimentally that accompanying plants influence
the growth of Aldrovanda in a positive way (Kaminski, 1987b). They
seem to produce some vital chemical substances. The nature of these chemicals
is still unknown. Some important stimulating neighbours are: Typha
latifolia, Stratiotes aloides, Phragmites australis,
Carex spp., and Hydrocharis morsus-ranae. Aldrovanda
only appreciaties the company of other plants as long as the vegetation
remains open. In Europe, Utricularia vulgaris or the related U.
australis are often found in the neighbourhood of Aldrovanda.
Although the two genera regularly occur together, Utricularia is
much less rare than Aldrovanda.
One might expect prey is useful
for every carnivorous plant, but from cultivation experience it appears
that a number of carnivorous plants can live perfectly without it. In
the case of Aldrovanda, prey plays an important role (Kaminski,
1987b). Zooplankton populations are always considerable in communities
with the plant. Probably zooplankton is a source of substances which Aldrovanda
can not take up from water in sufficient amount. Standing waters are preferred
as here there is little chance that the traps may be closed unncecessarily
by movements in the water.
A number of populations have
disappeared by the draining of lakes. Some habitats still exist but for
unclear reasons the plant has disappeared there too---most likely changes
in the water quality are reponsible. The water chemistry can be influenced
by precipitation and by runoff. Changes of water content do not necessarily
influence Aldrovanda directly. They might speed the decomposition
processes in the bottom sediment. As a result the nutrient levels in the
water rise (Bloemendaal & Roelofs, 1988). This situation might be
beneficial for competitor plants (macrophytes and algae) resulting in
dense plant communities with reduced light availability and CO2
depletion. For weak competitors like Aldrovanda, one or a combination
of the results of eutrophication might become fatal in time.
It is unclear at what growth
stage Aldrovanda is most susceptible. Probably the sprouting of
the turion is the most critical point. Changes in the structure and chemistry
of the bottom sediments (increased concentrations of toxic substances
like sulfides and ammonia) and reduction of the transparency of the water
might inhibit the germination process as suggested in studies of the decline
of Stratiotes aloides (Bloemendaal & Roelofs, 1988).
In temperate zones, the reproduction
of Aldrovanda only takes place vegetatively. This means that all
specimens of a stand are more or less genetically identical. So all individuals
are equally susceptible and react similarly to changed conditions. When
conditions become less favourable, the lack of genetic diversity is a
disadvantage and can lead to a rapid disappearence of the population (Weeda
et al., 1991). On the other hand, when the conditions are right
Aldrovanda might form extensive populations in a short time (Ohtaki
& Katagiri, 1974).
The cultivation of the Waterwheel
Plant is often said to be (extremely) difficult. Although it is not the
most ideal plant to start a carnivorous plant collection with, most problems
can be overcome by good planning, regular follow-up and sufficient knowledge
of the plant's needs.
To be successful, Aldrovanda's
ecological requirements need to be respected strictly (Ohtaki & Katagiri,
1974). The creation of a suitable aquatic habitat is not as easy as mixing
two parts peat to one part sand! Water chemistry is complicated and a
lot of factors interact with each other. If you start to create the biotope
after you have obtained Aldrovanda, you are probably acting too
late and are likely to lose the plant. Therefore, the habitat needs to
be prepared months in advance. As soon as the water conditions have become
suitable and stable, the Waterwheel Plant can be introduced safely.
The best place to grow Aldrovanda
is outdoors in an earthenware or plastic container. I grow my plants in
a round plastic lily pond 1 metre in diameter and 35 cm deep. It is important
to use a relatively shallow container with a large surface area. The smaller
the volume of your container, the more difficult it will be to create
and maintain stable conditions. The tank can be protected from curious
birds with a net. There are a few records of cultivation indoors (Ashida,
1934; Ohtaki & Katagiri, 1974), but I doubt that the plant can be
grown that way for prolonged periods.
Aldrovanda prefers places
with abundant light (Saito, 1972; Haldi, 1974; Hanabusa, 1974; Ohtaki
& Katagiri, 1974). Light is needed for photosynthesis and warms the
water, which the Waterwheel Plant definitely appreciates. It is still
unclear whether full or half-sun is best (Kaminski, 1987b). Too much direct
light might cause an explosive growth of algae.
The water temperature during
the growing season must be at least 16°C (61°F) with 32°C
(90°F) as a maximum, but ideal temperatures are 23--30°C (73--86°F)
(Saito, 1972). The lower the water temperature, the slower the growth,
and the carnivorous activity of Aldrovanda will be reduced. Prolonged
water temperatures of 29--31°C (84--88°F) cause the Waterwheel
Plant to flower (Saito, 1972). Prevent overheating by shading; in overheated
water algae might become a serious problem. In colder regions the water
temperature can be kept high by protecting the container from the wind
by insulating or burying it and by covering it with glass.
Aldrovanda prefers clean,
yellowish brown, peaty water with low concentrations of nitrogen and phosphorus.
Rainwater is fine, if it is not too spoiled. Alternatively one can use
deionized or peat-infused tap water (Mazrimas, 1974). A water depth of
20--30 cm is sufficient. To prevent accumulation of nutrients, it is recommended
that part of the water be replaced regularly. The carbonate hardness should
be kept medium high to high (test kits are available in garden centres
and aquarium shops) as it helps to minimise acidity (pH) fluctuations
and stimulates the decomposition of organic substances.
Carbon dioxide (CO2)
is a key element for photosynthesis. Shortage of it inevitably leads to
meagre growth and eventually death. Aldrovanda prefers waters with
a high CO2 concentration. Most carbon dioxide in water is produced
by bacteria which are responsible for the decay of organic substances.
Therefore, the more comfortable we make life for them, the more valuable
gas they will produce. While CO2 continuously diffuses into
the atmosphere and is consumed by terrestrial plants, there should be
a steady production to maintain the appropriate concentration. There are
several methods to raise CO2 levels artificially (Wilson, 1995).
What are the basic needs of bacterial life? They need oxygen and food
in the form of organic material. The main sources of oxygen in water are
diffusion from the atmosphere and production by water plants. So it is
advisable to grow enough submerged plants in the pond to maintain the
oxygen level. Artificial aeration should be applied with care as it not
only raises the oxygen level but also lowers the CO2 concentration.
A thick layer of sand on the
bottom of the container forms a stable anchoring base for the accompanying
rooted plants. Beneath this a small layer of peat can be useful too. Above
the sand comes a layer of half-decomposed (not fresh!) leaves of sedges,
Iris, reeds, arrowheads or rice grasses a few centimetres thick
(Saito, 1972; Haldi, 1974; Hanabusa, 1974; Mazrimas, 1974; Ohtaki &
Katagiri, 1974). The plant remains will help to maintain a low pH, keep
filamentous algae under control and act as a carbon dioxide and humic
acid source. The decomposition of this material gives the water a yellowish
brown colour. After some time the layer will become exhausted and must
be replaced with new material.
The water must be slightly
acidic with a pH between 5.6 and 6.8 (Saito, 1972; Haldi, 1974; Ohtaki
& Katagiri, 1974; Mazrimas, 1978). Check the pH regularly. If the
water is alkaline, then you have to lower the pH by replacing part of
the water and adding new plant remains.
Aldrovanda should not
be grown without other plants (Figure 6). The company of other water and
marsh plants helps to lower the nutrient levels in the water by direct
uptake and by stimulation of the decomposition process. Moreover it has
been confirmed experimentally that neighbouring plants influence the growth
of Aldrovanda in a positive way (Kaminski, 1987b). Sedges, Iris,
reeds, arrowheads and rice grasses are good companions (Hanabusa, 1974;
Ohtaki & Katagiri, 1974).
All small water crustaceans
are suitable as prey: Branchiopoda (e.g. Daphnia spp.), Copepoda
(e.g. Cyclops spp.), Ostracoda, etc. Look for a healthy, algae-free
mesotrophic pond nearby (hard to find in my neighbourhood!) and fish out
a quantity of microfauna. Introduce these organisms into the Aldrovanda
tank and if the water conditions are right, they will survive and reproduce.
Another important role of the microorganisms is to help prevent excessive
development of floating algae.
Good indicators of the plant's
health are the thickness of its apex (thick, onion-shaped---good; thin---bad),
the length of the adult plant (more than l cm---good) and the number of
branches (few---good; none---bad) (Saito, 1972; Mazrimas, 1978).
Healthy water should be clear,
straw coloured, contain a variety of small living microorganisms and be
as free from algae as possible.
Algae may endanger your Aldrovanda.
Weak plants become easily infected and will not survive. If the above
mentioned requirements are met, your plants will grow fast enough to withstand
algae quite well but this does not mean that nothing should be done about
it! Too much algae is an indication of bad water conditions. Of all algae,
filamentous algae are probably the worst to beat. Take away as much algae
as you can, change one or more water parameters and pray. Addition of
chemicals (alum, copper sulphate) only solve the problem temporarily and
are not appreciated by the Waterwheel Plant. Water snails can be useful
to minimize filamentous algae (Ohtaki & Katagiri, 1974) but some species
feed on higher plants like Aldrovanda, so be careful.
The best way to propagate Aldrovanda
is by stem cuttings a few centimetres in length (Mazrimas, 1978; Slack,
1986). Healthy plants do this work for you by forming numerous offshoots.
Prepare winter buds for prolonged
frost periods by insulating the container. Alternatively you can store
the turions in the refrigerator at 3--5°C (37--41°F) in cultivation
water or in a box filled with live Sphagnum.
Check your water and plants
regularly, they need a lot of attention ! Never add fertilisers (nitrogen/phosphorus/potassium)
to the water. Last but not least, do not give up too fast, finding the
right water balance is time-consuming. Good growing !
I dedicate this article to
L. Adamec and R. Kaminski who have been most helpful. Thanks also to all
others who provided material and valuable information. The Carnivorous
Plant Newsletter editors kindly refined the manuscript.
Adamec, L. 1994, private
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Front Cover: Flowering Aldrovanda
in cultivation. Photo by T. Nishida.
Rear Cover: This dystrophic Aldrovanda
lake is bordered by undisturbed littoral vegetation. Europe, 1993. Photo
by C. Breckpot.
Figure 1: Aldrovanda vesiculosa.
Photo by C. Breckpot.
Figure 2: In this characteristic
habitat Aldrovanda is accompanied by Stratiotes aloides
and Hydrocharis morsus-ranae. Europe, 1993. Photo by C. Breckpot.
Figure 3: Stand dominated by
Phragmites australis and Hydrocharis morsus-ranae. The largest
concentrations of Aldrovanda are found at places like this. It
is likely that wind and water currents contribute to the concentration
of plants. Europe, 1993. Photo by C. Breckpot.
Figure 4: Aldrovanda
in cultivation. Accompanying plants are Carex sp., Menyanthes
trifoliata, Phragmites australis and Thelypteris palustris.
Photo by C. Breckpot.