This is a guest post by Mackenzie Kwak.
As we Melburnians sweat through the last of summer’s heat, many of us seek refuge in the cooler and damper places around our city. Although less commonly visited, the Greater Melbourne region boasts an array of magnificent wetlands, and these warm periods are the perfect time to see some of our most magnificent wildflowers of the wetlands: the bladderworts.
Bladderworts are poorly known plants, owing to their small size and often brief flowering periods, which commonly occur during our warmer months when the urge to venture into wild places is often quelled by a brief glance at the thermometer. They are, however, some of the prettiest wildflowers that can be seen over the summer and also exhibit one of the rarest and most remarkable traits amongst plants: carnivory.
Being typically confined to damp places has not limited the spread of bladderworts across the globe. Today, bladderworts are found on every continent except Antarctica. Globally there are more than 200 species recognised, of which 10 can be found in Victoria. These species can be seen all through the state, flowering and growing from early spring through to autumn, depending on the species.
What is truly remarkable about bladderworts is their strange way of life. As they often grow in nutrient-limited habitats such as wetlands, seeps and ditches, they have developed the ability to trap and digest prey. The name bladderwort comes from the Middle English word ‘wort’ meaning plant, and ‘bladder’ which refers to the little traps that adorn their green stems.
The traps of bladderworts are very cleverly adapted to catching prey and consist of a round bladder with a small opening at the end, covered by a tiny trapdoor and a small trigger hair. Any water within the closed bladder is pumped out by the plant which creates a vacuum within the trap. When a small animal moves past and touches the trigger hair, the trapdoor is opened and the vacuum causes anything directly surrounding the trap, including the hapless creature, to be sucked in, where it is digested. Due to their small size, bladderworts feed on smaller quarry than some of Australia’s more commonly known carnivorous plants like sundews. Bladderworts are specialists of pondlife, creatures ranging in size from the near-microscopic paramecium all the way up to mosquito larvae.
Melbourne’s bladderworts can loosely be divided into two groups: the terrestrial species which produce tiny leaves and often live on the damp earth around wetlands or along seeps, and the aquatic species which are free-floating and grow at the warm surface of wetlands and lakes. Both groups are extremely well adapted to our conditions. Some species live as annuals, flowering during warm wet periods and producing copious amounts of seed before their little ponds dry up. Some live as perennials and form little buds which sink to the bottom and are buried in the mud as their wetlands dry up over the hottest part of summer. Still others sometimes occupy permanently flooded wetlands and grow all year round.
Amongst those enthusiastic about growing plants, particularly carnivorous plants, bladderworts are a popular choice. Many species are very easy to grow and will flower prolifically under the right conditions. However, it must be stressed that removing plants from the wild, although seemingly tempting, can contribute to the local extinction of some populations and is illegal in protected areas. Many wild-collected plants also often die upon removal from their habitats. There is a wide array of inexpensive and lovely native as well as imported exotic bladderworts that can be purchased from specialist nurseries or through dedicated societies for those interested in growing these beautiful plants at home.
So whether you are now keen to go out and catch your first glimpse of these remarkable wildflowers or want to give growing them at home a try, bladderworts never cease to fascinate people and will likely captivate you as well.
For more information, visit the website of the Victorian Carnivorous Plant Society.
Mackenzie Kwak is a zoologist with a broad interest in Australia's diverse flora and fauna. His research focuses on the biogeography, systematics and ecology of Australasian ectoparasites, particularly ticks, fleas and lice.
All photos sourced from Wikimedia Commons.