Commonly called “bladderworts”, Utricularia are a pandemic genus covering all the major continents and many of the continental islands. It is the largest of the carnivorous plant groups comprising some two hundred and fifteen species.
As with other genera of carnivorous plants Australia has the largest number of species of any one continent; though many of them are restricted to crocodile infested areas of the Northern Territory.
The various species can be subdivided into four broad categories depending on their habit and the situation in which they grow.
By far the commonest category grown, including our very own U. menziesii – one of only three species in the world to have red flowers.
Possess both aquatic and terrestrial habits. Many terrestrials can be grown as amphibians.
Produce the largest bladders, leaves and arguably, the most beautiful flowers within the genus. Many produce tubers and others just stolons which aid in their propagation.
By far the easiest to grow – all you need is peat, rainwater and a suitable container. Many of the South American species produce radial floats, which help support flower scapes as they grow through the surface of the water.
CARE AND CULTIVATION
U. dichotoma, a purple and yellow flowered native is an ideal subject for the beginner. It can be grown in a 150mm pot in standard mix (see below), placed in a suitable watering tray with the water level set at half the height of the pot. If the water is kept level with the top of the pot, the plant will develop an amphibious aspect, by sending out aquatic runners (into the surrounding water) upon which the bladders are very obvious.
It must be remembered that division is essential once your clump of Utricularia has multiplied and spread to the walls of the pot. Repotting tends to increase vigour and enhance flowering and if not repotted the plant may die.
Examples: U. tenella, U. lateriflora.
Most amphibious species are grown in a peat and sphagnum slurry. Many terrestrials can be grown amphibiously without ill effects; the advantage being the ability to view normally subterraneous bladders, with ease.
Example: U. caerulea.
These are best grown in some form of open basket type container, with holes in the sides, filled with either sphagnum moss, standard utricularia mix, or a combination of the two, with the standard mix on the bottom and sphagnum above. The baskets are lined with single sheets of newspaper or other suitable material, to prevent loss of the mix through the vents in the basket. In time the newspaper decomposes to leave a moss covered exterior which is quite attractive. The baskets are placed in suitable water containers, filled to half the height of the basket with rainwater.
These plants are tropical in nature, and in order to produce their larger sized leaves and spectacular flowers, need to be kept in a fairly humid environment.
Examples: No Australian representatives.
Aquatic Utricularia can be grown in any suitable container (from about six litres to small pools) filled with rainwater.
Aquatics are grown in rainwater to which very finely sieved peat moss has been added in the ratio of 1 peat moss to 10 volumes of water. Most of the peat moss sinks to the bottom, some matter is dissolved, while still more is held in suspension imparting a brownish tinge to the water.
Aquatics grow rapidly and can be multiplied by cutting at the base of each branching point to produce independently growing sprigs or simply left to enlarge and flower as a single plant.
Dormant aquatic buds, known as turions, will be left by each branch of a plant in winter. These will sprout again in spring so don’t dispose of them. In below freezing temperatures, some turions are known to sink, resurfacing again in the spring.
Any algae that develops on the water surface can be removed with sheets of tissue laid upon it. When removed the algae is retained on the surface of the tissue. Algae that grows on the plants can be killed by pouring water into the container with your plants. This stirs up the peat which clouds the water for some days and inhibits the algae from receiving the light necessary for it’s survival.
Examples: U. australis, U. gibba, and U. volubilis.
Standard Utricularia Mix:
3 parts peat, 1 part vermiculite, 1 part perlite, 1 part sand.
Variations such as coarse or fine sand, and different amounts of perlite, vermiculite etc. may be more suitable for particular species as some species may prefer a more open mix which allows more aeration of the roots.