The Bladderwort's (Utricularia species)

The Bladderwort's are the largest genus of carnivorous plants with approximately 230 species. They have a worldwide distribution, being found in most countries including several species here in England.

Generally, they are divided in to three groups-aquatic, terrestrial, and epiphytic, although there are exceptions to this. Aquatic species are normally free floating plants, found in open water in peat bogs-indeed this is the habitat that our own species are to be found. Terrestrial species live in permanently or seasonally waterlogged soils, and the epiphytes live on other plants-usually mosses on rocks or trees.

All species share the same characteristic small, bubble-like traps which are found all over the aquatic plants, and in the subterranean portions of the other two groups. They can't be called roots as the Bladderwort's have no true roots or leaves. Instead, they consist of modified stolons and rhizoids.

The traps themselves are the most highly developed structure of perhaps any plant, and are the fastest of all carnivorous plants. They are small (usually around 1-3mm in diameter), pressurised chambers complete with a trap door at one end.

Utricularia nelumbifolia Traps

When the trap is set and ready for capture, it's wall's are pulled in, giving them a concave appearence when seen from the outside and the bladder is sealed by the door. Any small swimming insect that blunders past the trap is guided towards the door by a series of bristles which bring the creature in to contact with tiny trigger hairs.

Once these are touched the door opens inwards and the insect and a quantity of water is sucked inside as the walls return to their convex states. The door then closes, and the water inside the trap is gradually pumped out leaving only the insect within. This whole scenario can take as little as a thousandth of a second. The trap is now re-set.

Digestive enzymes released in to the trap break down the insect, and the resulting nutrients are absorbed.

Cultivation.

As mentioned above the Bladderwort's are for cultivational purposes divided in to three groups, and each group has different requirements. The majority of plants grown in cultivation are either terrestrial or epiphytic, and it is these which are generally easier to maintain.

Terrestrial Species.

All of the plants listed below will thrive on a sunny windowsill or greenhouse/conservatory with bright light. They require a very high water level which can be as high as the soil surface during the summer months, and at about half way up the container during the winter. Only use rain or distilled water.

High temperatures are not a problem in the summer and a winter minimum of 10 degrees celcius will keep them happy. They should be grown in a 50:50 mix of moss peat and horticultural lime-free sand.

They quickly spread through a pot and some species do not flower until they appear rather cramped.

Utricularia sandersonii.

One of the commonest Bladdrewort's in cultivation, this African plant is one of the easiest and most rewarding species to grow, flowering profusely throughout the year. The white flowers are about a centimeter long with two upright 'spurs' which which look like a pair of ears.

Utricularia lateriflora Flower

Utricularia dichotoma.

This Australasian plant flowers mainly in the spring and summer months, and produces tall scapes to about 12 inches, topped by a pair of vivid purple blooms positioned back to back. The flower gives the impression of a small skirt which accounts for the plants common name of 'Fairy Aprons', and is touched with a small patch of yellow on the palate.

Utricularia lateriflora.

Another Australian species which produces small delicate pale purple flowers throughout the spring and summer months.

Utricularia fulva Flower.

Image Phil Wilson.

Utricularia pubescens.

Found on three continents, this Bladderwort has a huge range covering Asia, Africa, and South America. It is unusual in that it's 'leaves' are held flat to the ground and are attatched from underneath, and therefore look like many green discs on the soil surface. The upper surface of them is covered in a thick mucilage-the purpose of which is unknown. The flowers are produced in spring and summer, and in the typical form in cultivation are a pale lilac flower. They are vaguely similar to U. dichotoma in shape but are slightly larger.

U. fulva.

A tropical Australian species requiring high light and temperature levels to thrive. It is surely one of the most beautiful terrestrial species with apricot coloured flowers, splashed with burgundy on the palate. Stunning!

Epiphytic Species.

The epiphytic species are native to Central and South America. They include some of the most spectacular members of the genus, many with flowers which resemble orchids. In cultivation they generally enjoy a bright position, shaded from direct sunlight in the greenhouse or on a windowsill.

They like a high humidity which will be achieved by keeping the compost wet. They do not like to be as wet as the terrestrial species, and indeed should be kept in about 1 inch of rain or distilled water during the growing season, and just damp over winter when many species partially or completely lose their leaves.

A good substrate for these plants is straight sphagnum moss, and by growing the plant in a pond basket or similar, a good degree of air movement will exist around the roots. The leaves will also grow through the sides of the container-a situation which seems to suit these plants well.

Utricularia reniformis Leaves

Utricularia reniformis.

One of the largest species of Bladderwort, this Brazilian beauty is actually placed incorrectly with the epiphytes, as it is usually to be found growing as a terrestrial.

The leaves are large-to about 4 inches in diameter, and as the name implies are kidney shaped. They are held horizontally above the compost on dark red wiry stems which can be 8-10 inches high.

The spectacular flowers are produced with the first leaves in early spring. They are a beautiful lilac colour with two vertical yellow stripes on the palate which are edged in a darker purple. These can be 2-3 inches wide, and are produced two or three at a time on a scape which can be two feet high.

Utricularia nelumbifolia Leaf

Utricularia nelumbifolia.

Similar in shape to U. reniformis, but with a circular peltate leaf. It requires the same conditions, and spreads by means of long stolons which it throws out and in to surrounding pots.