Greater bladderwort (Utricularia macrorhiza) is a free-floating aquatic plant. The stems, which can grow to three feet or more in length, do not have roots and float or are partially submerged in ponds, lakes and sluggish streams from low to mid elevations. This native perennial can be found in all of North America, except Louisiana, and also in parts of temperate Eastern Asia.
The leaves of greater bladderwort are alternate and divided into numerous thread-like segments. Amid the leaves are small, buoyant, valve-lidded bladders that trap small animals. Greater bladderwort is a carnivorous plant.
Each greater bladderwort bladder is closed at the narrow end by a water-tight, valve-like “door” with four stiff trigger bristles on the outer surface. When set the bladder has a partial vacuum. When a tiny crustacean or other small animal touches the trigger hairs the door opens slightly and the bladder walls expand resulting in a sudden rush of water into the bladder. The rushing water engulfs the prey and moves it into the bladder. The door closes trapping the prey. Enzymes or bacteria, there is some debate about this, dissolve the animal and its nutrients are then absorbed by the plant. Fascinating!
The greater bladderwort inflorescence is made up of 5 to 20 deep yellow, snapdragon-shaped flowers atop a stout, above-water stalk. The lower lip has a short, sac-like spur and red venation. Two green sepals surround the corolla.
The fruits of greater bladderwort are capsules on downcurved stalks. The underwater stems may produce turions – overwintering vegetative buds.
A synonym for U macrorhiza is Utricularia vulgaris. The genus name comes from the Latin “utriculus” meaning a small bag or bladder. “With large roots or root stocks” is the meaning of “macrorhiza”. Since the plant apparently does not have roots this designation is, at least to me, confusing.
These greater bladderwort specimens were photographed in the canal near the weir across from Hall Pond at Ash Creek Wildlife Area (Lassen County CA).