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Utricularia
Probably one of the most unassuming carnivorous plants, Utriculariaare widespread across most of the world. The traps consist of tiny bladders hidden beneath the soil or underwater. These bladders force water out of them, building up a pressure on the trapdoor. When an unsuspecting victim wanders by and brushes up against one of the surrounding trigger hairs, the trap door opens, and water rushes in, sucking in the prey with it. Smaller prey is completely trapped inside the bladder, which then begins its digestive process. Larger prey is trapped partially in the bladder, which begins to digest it, reset itself, and is set off again be the end still left outside struggling. Not a nice way to go!
The bladders range in size from microscopic, up to half an inch or larger. Prey consists of aquatic crustaceans, insect larvae, and even small minnows.
The bladderworts can be split up into several different categories, based on where they live. The terrestrial varieties live in soggy soils with their 'leaves' (bladderworts don't have true leaves, stems, or roots) just above soil level. Their branching network of bladders are below ground.
The second group, and probably the most common, are the aquatics. These bladderworts grow completely underwater, except in late summer when they produce flower stalks which break through the surface of the water. The sight of several hundred Utriculariain bloom is quite impressive.
Tuberous Utriculariaare native to Australia, and grow only during the wet, cool winters. When drying, hot conditions arrive in summer, the plants die back to underground tubers, which store up energy for the next growing season. While not many species have been described, it's likely that there are more to be discovered.
The final, and most impressive in leaf and flower, are the epiphytes. These bladderworts grow on the branches of trees, and in organic matter. Most have large leaves and produce flowers that can reach up to two inches in diameter and have been compared in beauty to the orchids.
Species
There are over two hundred species, with new ones being discovered all the time. An excellent reference for the dedicated Utric enthusiast is Taylor's monograph on Utriculariawhich contains descriptions of all described species. This is available through Kew Botanical Gardens, but is expensive (over $100 Canadian).
Soil and Containers
This depends on what type of Utriculariayou are growing. Aquatics need a watertight vessel, with about a handful of peat thrown in per gallon of water. They are not as sensitive to algae as Aldrovandais.
Terrestrial varieties like a 1:1 mix of sand and peat moss. Keep this wet to soggy at all times. They also appreciate the occasionaly flooding, which triggers flowering in some of the shyer species. These are not space consumers, I've grown them in 1 inch containers. A 4 inch container allows them to put on a more impressive display of flowers.
Epiphytes like a loose, open mixture such as an equal mix of sphagnum moss, orchid bark, perlite, sand, and a bit of peat moss. Too much peat moss will inhibit growth. Containers range from 4 inch to 12 inches, depending on the species.
Tuberous varieties need a sandy mixture of 2 parts horticultural sand to 1 part peat moss. This is so that the soil can be dried out quickly when necessary.
Climate
Since the Utriculariaare so widespread, it is hard to generalize on the climate. Naturally, they enjoy high humidity and moisture levels, and about half to full sunlight. The temperate aquatic varieties will form turions, tight bunches of leaves, during the fall to survive in the winter. These sink into the sediment and wait for spring. If you want, these can be removed and placed in the main compartment of the refrigerator, keeping them moist at all times.
Tuberous varieties have to have their dormancy respected. When the leaves dies in the late spring, watering levels should be cut back completely, allowing the soil to become dry. In the fall, when new growth is noticed, you can begin watering again.
Propagation
For most species, this merely involves taking a clump of leaves and replanting in a new pot. For aquatic varieties, cut off a 2 inch section and place in a new container.
Seed is used most often for growing the epiphytes. This should be sown on its preferred medium without burying. Germination occurs in a couple of weeks, and, depending on the species may take from 3 months to 3 years to get a mature, flowering plant.
Seasonal Care
While I have not found them to be subject to fungus, I like to remove spent flowers and dead leaves if possible. Changing of the water and soil is necessary every couple of years, and will encourage more flowers to be formed.
Terrestrial varieties appreciate the occasional flooding. The tuberous varieties must have their dormancies respected.
Pests and Diseases
As I said above, I have not found the Utriculariais particularly susceptible to fungus. Treat with a fungicide if this does happen.
Aphids just love the flower stalks of Utrics. When this happens, remove the flower stalks. A bad infestation requires spray with an appropriate pesticide, though I have found this can set back the plant.