Flower:

Raceme of 1 to 4 bright yellow 1/3-inch snapdragon-like blooms at the top of a mostly naked reddish green stem emerging from the water. The flower has a large lower lip fanning out, an inflated pouch mid-lip, a broadly triangular upper lip half as long as the lower lip, and a stout curved spur underneath slightly shorter than the lower lip. The center pouch and upper lip typically have red venation. Each flower has a slender green stalk.

Leaves and stem:

Leaves are alternate, elliptic to nearly round in outline, up to ¾ inch in diameter, palmately divided near the base into 2 or 3 main divisions, the segments flattened though may appear thread-like, and the primary divisions each forked 2 to 5 times. Small bladders for capturing micro-organisms are present on specialized, leafless stems, but nearly impossible to observe without careful extraction from the boggy mud in which they are emersed.

Underwater stems may produce turions (overwintering, vegetative buds). Stems are up to 6 inches long, sparsely branched, leafy and with fine, fibrous roots. The flowering stem has a few minute scale-like leaves alternately attached.

Fruit:

Fruit is a round capsule about 1/8 inch diameter

Notes:

Flat-leaved Bladderwort is another one of Minnesota's carnivorous plant species. While it is not as widespread as the Common Bladderwort (Utricularia vulgaris), it can be frequently happened upon searching shallow marshy areas of many lakes and open wetlands. There are 8 bladderwort species in Minnesota, most with yellow flowers and similar leaves. 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. Flat-leaved Bladderwort bladders are mostly unseen on leafless stems, the lower lip on the flower is twice as large as the upper lip, the pouch and upper lip typically have red venation, flowers are up to about 1/3 inch long, and leaves are palmately divided then forked. Its leaves are most similar to Lesser Bladderwort (Utricularia minor), which also has palmately divided leaves, but are less than 2/3 inch diameter and will have bladders. 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.