U. sandersonii--a Siren from Utricularia
(Bulletin of the A.C.P.S., 1994, 13:1, 6.)
Of all the genera of carnivorous plants,
Utricularia reigns supreme. For in addition to containing
more species than any other carnivorous genus, it is also the most
widespread in global range. Indeed--it is likely that the
the carnivorous plant in the wild closest to you at this moment is a
Utricularia.
Yet for its preeminence, why is
the genus so under-represented in cultivation?
Surely part of the answer lies in size. Most species have small above-ground
portions--none of the downward pointing hairs, waxy cuticles, or droplets
of adhesive mucous, all of which are the meat and drink (especially meat) for
the carnivorous plant grower. Another reason the genus is so often neglected
in collections relates to sheer horror factor. Part
of the perversity of the carnivorous plant grower is the thrill of revulsion
and fascination derived by seeing a plant strike back at the invertebrate
world which is so often its foe. But
Utricularia do their dirty work in the dirt or underwater, so the
grower is (unfortunately) spared a view of the prey's horrible demise.
These handicaps are well illustrated by the
well intentioned but rather pathetic compliment Adrian Slack (1979) paid to
plants in the genus: "The tiny grass-like
leaves of some of these species are often
hidden by moss growth....their continued existence is at once evident
when they flower."
I recall first reading Slack's words when I was in the
early stages of my carnivorous plant career. I thought, "What a silly
plant that is! I want to see my plants all the time--preferably
in gruesome action--and not just when they are flowering."
But with time I have become enlightened.
It is true that the plants are not big. (The leaves of U. longifolia
reach a meter in length only extremely rarely,
and the largest U. macrorhiza branches
I have seen in the wild were barely 1.5 meters long.) It is true that the
plants are not particularly hideous in carnivorous action. (Although seeing
U. striata drown struggling mosquito larvae by trapping their heads
once gave me claustrophobic dread.
And supremely dreadful was watching a worm, held at each end by two bladders,
struggle for longer than a week while it was slowly digested alive.)
But a great prize awarded the horticulturist is that
after the beastly bladders have glutted their
appetites, and the plants have grown sufficiently large,
they salute the grower with a display of flowers, the beauty of which is
unbeaten by any other carnivorous genus. Truly, people grow
Utricularia not only for their horrific carnivory, but also
for the incredible diversity of flowers, the surprising variation
of leaf morphology, and finally the horticultural challenge presented
by a huge genus containing terrestrials, epiphytes, suspended aquatics,
affixed subaquatics, lithophytes, and many other types of
plants.
The plant U. sandersonii is a delightful species. It is in the
section of the genus called Calpidisca, which also
contains nine other species, including the frequently grown
U. livida and U. bisquamata (the latter is often incorrectly
called U. capensis--a botanically invalid name). Keying species
of Utricularia is often a subtle or technical process, but this
is not the case with U. sandersonii--the flowers are absolutely
unique. No other species is even remotely similar,
so if you have a plant that looks like the photograph, its identification
is not in doubt. Perhaps the species which is most closely related is
U. livida, but it can easily be distinguished from
U. sandersonii because its upper corolla lip is not split into
the two bunny-ears that are so entertaining on U. sandersonii.
The leaves of U. sandersonii are unlike those of the common
weed-species such as U. subulata, U. bisquamata
or U. lateriflora. They are cuneate--a narrow wedge shape
that usually flares slightly before terminating abruptly.
Taylor (1989) writes that these plants come from a small area in
South Africa where they often
grow on wet, vertical rock faces, at an
elevation of 210-1200 meters. In spite of these peculiar conditions
in the wild, the plant requires no special cultural methods.
I use a method that works for almost all the tropical Utricularia
except aquatics and semi-aquatics, or the large species
that do better in live Sphagnum.
When CPers refer to "standard Utric culture,"
the following procedure (or close to it) is usually what is meant.
Use either pure dead
milled Sphagnum or a 2:1 peat-sand mix in a 5 cm (2") pot. I use water
purified by distillation or reverse osmosis. I know some growers are
fortunate enough to be able to use tap water, but my Arizona tap water
contains far too many dissolved chemicals. The soil should be permanently
moist--I keep my pots in trays filled with enough water so the
water table is just a few cm beneath the soil surface.
Keep them warm year round, around 20-30°C
(68-86°F). If the plants are kept too
cool they grow extremely slowly, while if overheated the flowers are pale
in colour and do not last as long.
Since they are found in shady places in the
wild I give them medium light. While this means some shade in the greenhouse,
the light available in most 4-6 fluorescent bulb terrarium set-ups is
fine. In good conditions, U. sandersonii
grows quickly. After only a few months it will cover
the surface of a 5 cm pot with its little leaves.
It is easy to propagate--carefully detach from the mother pot
a hunk of leaves, stolons, and bladders, and
plant it in a new pot. In time you will be rewarded with a dense display of
lovely flowers. Despite a few half-hearted
attempts at selfing and cross pollination, I have not
been able to yield seed from my plants.
There are more than two hundred species of Utricularia,
and the majority are in cultivation. Once you start to grow them, there
is little chance you will ever stop. But first you must modify your
motivation for growing plants--don't restrict yourself to carnivores
like Drosera that bear modified leaves.
The strength of Utricularia is
in its flowers--appreciate that aspect of this genus. And what better choice
is there to introduce you to the genus than the easily grown and floriferous
U. sandersonii? The beautiful
siren calls to you from its slippery home of water-splashed rocks,
the trap is set and the unwary grower is easily seduced--all
you must do is follow its song!
References:
Slack, Adrian. (1979). Carnivorous Plants, MIT Press, Cambridge.
Taylor, Peter. (1989). The Genus Utricularia, Royal Botanic Gardens, Kew.