The Biology and Cultivation of Red Australian
Academy of Sciences of the Czech Republic Institute of Botany
Dukelská 145 CZ-379 82 Trebon, Czech Republic email@example.com
Keywords: cultivation: Aldrovanda.
Aldrovanda vesiculosa L. (Droseraceae) is
an attractive but very rare aquatic carnivorous plant from the Old World.
In the last five years, Australians have been trying to grow two "red"
strains of Aldrovanda endemic to their country (Wilson, 1995; Daly,
1997a, 1997b, 1997c, 1998; Schell, 1997). Among other desirable attributes,
these varieties do not require a winter dormancy. In this paper I present
notes pertaining to these Australian plants--a more general discussion
of Aldrovanda can be found elsewhere (cf. Breckpot, 1997;
In Australia, Aldrovanda is far less common than
it once was, and it is designated a rare and threatened plant. In this
article I discuss specimens from a poor site at Girraween Lagoon, approximately
30 km southeast of Darwin (Wilson, 1995), and a swamp near Batemans Bay
at the East Coast, approximately 110 km southeast of Canberra (S. Jacobs,
personal communication). In contrast with most European sites, dense growths
of other aquatic plants grow with Aldrovanda at Australian sites
(Wilson, 1995; S. Jacobs, personal communication).
There are four main differences between the European temperate
and the Australian (sub)tropical strains of Aldrovanda I have studied:
the colors of the plants, their overwintering characteristics, the particulars
of their of axillary buds, and their different sensitivities to boron.
I discuss the first three below. The details of the boron sensitivities
are described in the next section.
Color: The European and Japanese plants are light green
and contain a great deal of plumbagin (a sulphur-yellow pigment) but no
anthocyanins. The color of Australian plants may be the same green, or
slightly rose to deep purple (Figure 1) because they contain anthocyanins
as well as plumbagin. Irradiance is the main factor regulating the color
of the Australian plants--if the plants are exposed to sunshine for at
least two hours a day they become red in summer and rose in winter. If
grown indoors, supplemental fluorescent lights help the plants become
Overwintering Characters: In contrast with the European
and Japanese Aldrovanda, strains from both Australian sites can
grow year round under natural light at a daily temperature of about 18°C
or higher (at 18-19°C, the growth is very slow and the plants are
in the winter growth form). In an indoor aquarium under natural light,
the growth rate of east coast plants in June (spring) is approximately
0.7 new leaf whorls per day. The plants average 23-26 cm long, with 31-35
adult leaf whorls. During the winter, the plants are much shorter (3.3-12.4
cm, 10.5-19 whorls) and their growth rates are only approximately 0.2-0.5
whorls per day.
Even though they may be grown continuously, Australian Aldrovanda
can be stimulated into producing turions if the plants are subjected to
daily temperatures below approximately 18°C (cf. Adamec, 1999). In
my outdoor culture, Australian plants started forming turions in early
October (autumn), one month later than the temperate strains did. Shoots
died very slowly (even at 8-10°C) and were still attached very firmly
to the turions. At the end of October, shoots with turions sank to the
The turions of Australian strains are more weakly dormant
than temperate strains are (cf. Adamec, 1999). When plants forming turions
were transferred from the Domanínsk_ wetland to an indoor aquarium
at 19-24°C (on 27 September), they immediately resumed growth. However,
when Australian strains were transferred from the outdoor culture (6-7°C)
to indoors (18-20°C) at the end of October they stayed dormant for
several weeks. (It is worthwhile to note that these plants demonstrated
interesting characteristics. During the first two weeks, big axillary
buds formed on the shoots close to the turions, and new plants started
growing from these buds. Thus, the dormancy is only confined to main-shoot
turions.) In summary, the turions of north Australian plants were more
deeply dormant than those from the east coast, and overall, the Australian
strains are not as adapted to cold overwintering as the temperate ones
Axillary Buds: Long specimens of Australian plants growing
both indoors and outdoors in summer frequently form branches from axillary
buds (i.e. 1-6 buds per plant). In contrast, temperate strains form axillary
branches poorly, and mainly when their apices are damaged.
In outdoor experiments, both strains of Australian Aldrovanda
grew and proliferated well from early June to late October 1998 (after
Adamec & Tich_, 1997). Plants from north Australia grew vigorously
in a nylon enclosure in a shallow dystrophic wetland near Trebon, where
Polish Aldrovanda had been grown previously (Adamec, 1995). While
the doubling time of apices (15.5-26.0 days) was the same as for the Polish
Aldrovanda, the Australian plants branched much more frequently--branches
were formed every 3.3-4.5 leaf whorls, as opposed to approximately every
6 whorls as in the Polish plants. Branch proliferation almost stopped
in late August and the plants shortened gradually to ca 1.8 cm.
How to grow Australian Aldrovanda
To grow Australian Aldrovanda successfully you must
modify the methods that are appropriate for temperate strains (see Adamec,
1997; also Wilson, 1995; Daly, 1997a, 1997b, 1997c, 1998; Schell, 1997).
In summary, the Australian strains can be grown outdoors in big containers
or small aquaria as normal (Figure 2), from May to October (i.e. spring
to autumn), and then transferred to indoor aquaria. Turions can probably
overwinter in water in a refrigerator at 3-5°C. It is convenient
to grow them indoors in small aquaria (3-20 liter) under natural light
at temperatures exceeding 18°C for the whole year. It is the best
if the aquaria stand close to an east or southeast oriented window so
the plants are irradiated by direct morning sunlight for a few hours each
day. This should be supplemented by diffuse light for the rest of the
day. A 10 Watt fluorescent lamp can help. Australian Aldrovanda
tolerate less irradiance but higher temperatures (optimum 25-29°C;
maximum 34°C) than do temperate strains. In order to reduce the growth
of filamentous algae, the aquarium wall facing the sun should be shaded
by a sheet of paper from about 2 cm below the water surface to the bottom.
During the summer, the aquarium should be shaded with a sheet of fine
paper to keep it cool.
In indoor aquaria, Australian Aldrovanda flower richly
in summer at 20-29°C. The flower stalks of the Australian ones were
red (Figure 1). No flower set seeds, but they do in the wild (S. Jacobs,
D. Wilson, personal communication).
Robust sedge or reed litter (i.e., dry dead leaves or straw
collected in late winter) is the required substrate. The optimum amount
of dry litter is approximately 4+0.5 g per three-liter aquarium.
A dose of fresh litter lasts for 2-3 months. The water pH should be 6.0-7.5.
A high CO2 concentration >0.1 mmol/l is necessary for vigorous
growth of Aldrovanda, and you may wish to add CO2 to
the water (see the article about CO2 generators in this issue,
on page xx).
As described for temperate Aldrovanda (Adamec, 1997)
the cultivation water should be rather poor in N and P to control algal
growth. In one aquarium, very low concentrations were measured (e.g.,
in µg/l: PO4-P, 10.2; NH4+-N, 0.0; NO3--N,
11.8; NO2--N, 6.5). You may add 1-2 small water
snails (e.g. Planorbis) to a three-liter aquarium, but too many
foul the water (Underwood, 1991).
In a previous paper (Adamec, 1997), I described how a disorder
commonly exhibited by cultivated Aldrovanda was determined to be
a boron deficiency. It has been confirmed recently that an addition of
0.05 ml/l of complete microelement solution (see Table I) once or twice
a year cures the plants. I have often observed this disorder in the Australian
strains, but these plants are rather sensitive to boron--adding 0.5 mg/l
of H3BO3 can damage them. However, the addition
of 0.03-0.05 ml/l of the new, complete microelement solution will cure
the plants of this disorder. Symptoms of iron deficiency (yellowish but
healthy apices) are suppressed by an addition of 1-2 mg/l of FeSO4.7H2O
or 2-3 mg/l of Fe-EDTA.
Table I. Composition of the Gaffron microelement solution
and final concentrations of salts and elements after an addition of 0.05
ml of the stock solution to one liter of water.
Final concentration of ...
Stock solution (mg/l)
... the salt (µg/l)
.... the element (nmol/l)
Acknowledgements: I am very grateful to Dr. Surrey Jacobs
and Mr. Denis Daly for sending me the Australian plants of Aldrovanda
and providing interesting data.
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