Flower:

Raceme of up to 20 bright yellow ½ to ¾-inch snapdragon-like flowers at the top of a stout reddish green stem, emerging up to 8 inches above the waterline. Flowers are generally globular; the broad lower lip angles upward, the smaller upper lip fans above it, erect or angled towards the lower lip. A stout spur is below, at least half as long as the lower lip, extending out horizontally and curving upward. Flowers have finely articulated red venation on the protuberance of the lower lip. Behind the flower are 2 small, egg-shaped, green sepals, the lower with a rounded or notched tip, the upper slightly larger than the lower and with a more pointed tip. Each flower has a short green stalk.

Leaves and stem:

Plant is free floating and has no roots. Leaves are alternate, ¾ to 2 inches long, with 1 or 2 main divisions from the base, each with alternate branches, a branch forked a few to several times into thread-like segments, and the central stalk often zig-zagging between the branches. Small reddish bladders extend from leaf filament axils. Leaves are mostly submerged though this species can grow above the waterline in wet muck.

Underwater stems are green to reddish and may produce turions (overwintering, vegetative buds), which can be over 1 inch in diameter. Stems are up to 8 inches long, few-branched, and often zigzag between the alternate leaves. Flowering stems have a few widely spaced, alternately attached, scale-like leaves. All parts of plant are smooth.

Fruit:

Fruit is a round capsule less than ¼ inch in diameter, with the stub of the style persisting at the tip.

Notes:

Common Bladderwort, sometimes known by synonym Utricularia macrorhiza, is a very widespread species within Minnesota, the US and throughout the Northern Hemisphere, usually overlooked by nature enthusiasts but a common sight in wet ditches and wetlands across the state. Bladderwort is a carnivorous species many have learned about in their junior high/middle school science classes. Small bladders are inflated sacs that are triggered to ensnare tiny aquatic organisms. Those of Common Bladderwort fill with air to keep the plant afloat during the flowering period and fill with water to sink the plant when it goes into dormancy. There are 8 bladderwort species in Minnesota. Distinguishing features are the size and shape of the spur, the general shape of the flowers, including relative sizes of the upper and lower lips, the bladder size and location, and leaf arrangement. Common Bladderwort has the largest flowers of the Minnesota species, a short, stout spur that extends horizontally, relatively large bladders easily visible in the thread-like leaves, leaves that have alternating branches that are forked several times and a zig-zagging central stalk. It is also a free-floating species. Some populations never flower but the vegetative plants can be seen if you're looking. Fragments of vegetative leaves can be indistinguishable from those of Hidden-fruit Bladderwort (U. geminiscapa), but the bog habitat of U. geminiscapa may be sufficient to rule it out. Although the commonly held view is that the bladders of bladderworts are for capturing and digesting microorganisms that provide the plant with nutrients, bladders more often have been observed to contain communities of microorganisms (bacteria, algae, and diatoms) living in the bladders, not as prey, suggesting that the bladders may also, and perhaps more importantly, serve to establish mutually beneficial relationships with some microorganisms.