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The New Eng lan d Carnivo rous Plant Society
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The Bladderwort
Utricularia
Bladderwort is the common name given to the
plants of the genus Utricularia, the largest
genus of carnivorous plants. There are over
two hundred species found in fresh water and
wet soil. Bladderworts are most often
cultivated for their flowers, which are often
compared with those of snapdragons and
orchids. The anatomy also diverges greatly
from the usual plant structures: they have no
true roots, their leaves are considered by
many to not be true leaves at all, and stems
are nearly absent in all but the most primitive
species. Most bladderworts are very small
clusters of plants.
Tuberous Utricularia are native to Australia,
and grow only during the wet, cool winters.
When drying, hot conditions arrive in summer,
the plants go dormant and form underground
tubers, which store up energy for the next
growing season.
How They Trap Food: The tiny trapping devices of Utricularia are usually buried
within the soil, or in the case of aquatic species, tangled in floating masses of aquatic
weeds. Tiny though it may be, its complexity is unrivalled in the world of carnivorous
plants. It consists of a sac, (usually between .5 and 2 mm, although giants of the genus
can reach a whole centimeter), with an inward-opening trapdoor on one side, levered by
tiny trigger-hairs. The plant pumps water out of the sac, creating a lower pressure inside
the trap. When an unsuspecting organism of suitable scale ventures too near and trips one
of the trigger hairs, the door opens, the victim is sucked in, and the door shuts behind it.
The whole process can occur within ten to fifteen thousandths of a second. Once inside
enzymes secreted by the plant digest the prey, and the resulting nutrients are absorbed.
Typical Prey:
Terrestrial species tend to have tiny traps, and feed on minute prey
such as protozoa and rotifers swimming in water-saturated soil. However, in aquatic
species, the bladders are larger (sometimes exceeding 5 mm in diameter) and can feed
on more substantial prey such as water fleas (Daphnia) and even fish fry, mosquito larvae
and new tadpoles.
Where it Lives:
Bladderworts are found on every continent in the world except
Antarctica.
Basic Care: Most Utricularia are generally easy to grow. Many people use the tray
method to grow them. Most prefer wet potting media, so they can be grown in
undrained containers. Occasional flooding of the container may induce flowering in
some species. Terrestrial varieties like a 1:1 mix of sand and peat moss and to be kept
wet. Epiphytes like a loose, open mixture such as an equal mix of sphagnum moss,
orchid bark, perlite, sand, and a bit of peat moss. Tuberous varieties need a sandy
mixture of 2 parts horticultural sand to 1 part peat moss. Most can easily be grown in a
terrarium provided with artificial lighting.