Utricularia (Bladderwort):
Habitat:
With more than 220 species, the Utricularia is the most species-rich among all carnivorous plant genera. Except for Antarctica, they inhabit all continents whereby they especially grow in extreme habitats ranging from fast-flowing waters to periodically desiccating sand regions. Scientifically, the Utricularia is being demarcated into two groups, namely either terrestrial or aquatic species. The terrestrial species, which amount to approximately 80% of the genus and have rather tiny bladders, often grow alongside other carnivorous plant genera in swampy regions characterised by wet soil and waterlogging. The other 20% are aquatic species with larger bladders, floating freely on the surface of ponds, streams and sometimes waterfalls with higher acidity water.
Cultivation:
The requirements of species within the Utricularia genus can vary more or less depending on whether they belong to the terrestrial or aquatic group. Terrestrial ones can be found much more frequently in garden centers than aquatic representatives, particularly because of their predominant number of species. Most unproblematic are, for example, the Utricularia livida or Utricularia microcalyx, which when planted out into a pot very quickly spread over the moist sphagnum without stealing other plants space for growth. Compared to many carnivorous genera which can quickly decay when subjected to waterlogging, a decently high water level proves very conducive for the plant's health and growth. Another peculiarity is that the Utricularia doesn't like direct sunlight that much, but prefers semi-shade spots to unleash its growth potential. These terrestrial species are ideally cultivated indoors, and thanks to their low demands they are a beginner's best choice. Aquatic species, for example the Utricularia vulgaris or Utricularia australis, are relatively easy in cultivation as well, the main difference being that they should be either cultivated in a low-nutrient indoor aquarium or an outdoor garden pond. Here, curbing growth of algae is important to ensure the Utricularia's healthy development. Too much algae will rapidly entail the plants decay. Cool temperatures not higher than 12°C during winter contribute positively to these species' blossoming in early spring, while they also have a good degree of hardiness allowing them to withstand frosts. Should the frost become too severe during the outdoor cultivation, some protection is recommended.
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Trap mechanism:
All Utricularia species have suction traps, the only distinction that can be made between terrestrial and aquatic species is that the former have smaller bladders not bigger than 2mm at max, while aquatic species have bladders that can become up to 1.2cm in size. The Utricularia is said to have the most sophisticated trap mechanism in the plant kingdom. They are active traps in that they pump water through the thin and transparent bladder walls, creating negative pressure. At the same time, the trap entrance is coated with viscous mucilage, while sugary secretions lure the insect to the trigger bristles, which when activated will perform the catching process within split seconds. The pumped-up water will then soak the prey deeper into the trap, where specific cells actuate the digestive process. After about 15 minutes during which the plant will create negative pressure anew the trap will be ready for use again. Whereas visibly observing the trap mechanism can be very difficult due to the rapidity of the process, cracking sounds are a much more obvious indicator of trap activity.
Much Love and Light,
Alex
Literature inspiration: Kosmos Garten: Fleischfressende Pflanzen