WATERWHEEL Aldrovanda vesiculosa
Aldrovanda vesiculosa, commonly known as the waterwheel plant, captures small aquatic invertebrates using traps similar to those of the Venus flytrap. The traps are arranged in whorls around a central, free-floating stem, giving rise to the common name. This is one of the few plant species capable of rapid movement.
A. vesiculosa has declined over the last century to only 50 confirmed extant populations worldwide. These are spread across Europe, Africa, Asia and Australia.
Aldrovanda vesiculosa is a rootless aquatic plant. The plant consists of floating stems reaching a length of 6–40 cm (2–16 in). The trap leaves grow in whorls of between 5 and 9 in close succession along the plant's central stem. The actual traps are held by petioles which hold air sacks that aid in flotation. One end of the stem continually grows while the other end dies off. Growth is quite rapid (4–9 mm (0.16–0.35 in) per day, so that in optimal conditions a new whorl is produced once or more each day.
The actual traps consist of two lobes which fold together to form a snap-trap similar to that of the Venus fly trap, except that it is smaller and located underwater. These traps, which are twisted so that the trap openings point outward, are lined on the inside by a fine coating of trigger hairs, snapping shut in response to contact with aquatic invertebrates and trapping them. The closing of this trap takes 10–20 milliseconds, making it one of the fastest examples of plant movement in the kingdom. This trapping is only possible in warm conditions of at least 20 °C (68 °F). Each trap is surrounded by between four and six 6–8 mm long bristles that prevent triggering of traps by debris in the water.
The small, solitary white flowers of A. vesiculosa are supported above the water level by short peduncles which arise from whorl axes. The flower only opens for a few hours, after which the structure is brought back beneath the water level for seed production.
Aldrovanda vesiculosa is the most widely distributed carnivorous plant species, native to Europe, Asia, Africa, and Australia. Aldrovanda is spread mainly through the movement of waterfowl: plants sticking to the feet of a bird are transported to the next aquatic destination on the bird's route. As a result, most Aldrovanda populations are located along avian migratory routes. Throughout the last century the species has become increasingly rare, listed as extinct in an increasingly large number of countries.
A. vesiculosa prefers clean, shallow, warm standing water with bright light, low nutrient levels and a slightly acidic pH (around 6).
Seeds per pack: 2 rare seeds
Germination: Waterwheel seeds can be challenging to germinate. Rainwater is best for planting. Place the seeds on moist paper-towel, and put the towel in a zipper-seal bag, place in the fridge for 4-6 weeks. Do not let freeze. Then, once the cold period is over, place the seeds in water that is room temperature, or slightly warmer. The water can be kept fresh by occasional changing, or with the use of a blubber or water fountain to circulate the water (the water should not be turbulent). Patience is needed for germination, though they are well worth the wait!