Utricularia macrorhiza Leconte

Common bladderwort, bladderwort

Bladderwort is a native of the Northern Hemisphere, includ­ing most of North America and parts of temperate eastern Asia. Except for occasional racemes of yellow flowers, bladderwort remains submersed in lakes, ponds, wet marshes, and rivers and streams up to about 6′ (1.8 m) deep. An underwater rootlike structure contains numerous “blad­ders”—small pouches that help keep the plant near the surface during flowering, then sink it during dormancy periods. But the bladders have another purpose. Common bladder­wort is actually carniverous, and the bladders are spring-loaded traps that suck in water and small organ­isms, and digest them with enzymes and bacteria. They snap shut in about ⅟₄₆₀th of a second!

Plants: Plants are not anchored and float freely, close to the surface. Rootlike structures are leaves. Underwater stems sometimes produce turions—overwintering, vegetative buds—up to about 1″ (2.5 cm) around. (In many of the photos, the water surface is covered with numerous green dots. These are duckweed, not bladderwort.)

Leaves: Leaves are alternate, ¾–2″ (1.9–5 cm) long, on a zig-zagged stalk with one or two main divisions from the base, these in turn forked into threadlike sections. They look more like a cloud of algae than a system of leaves. Bladders start out greenish and transparent, becoming dark red or brown to black. They are more than 1/16″ (2 mm) in size.

Flowers: A stalk up to about 10″ (25 cm) in height contains a raceme of 6-20 yellow flowers, each resembling snap­dragons and about ½–¾″ (1.3–1.9 cm) in size. They appear from late May to September.

Fruits: Round capsules less than ¼″ (6.3 mm) around.

Habitats: Mostly in ponds and lakes, but also in slow-moving streams and rivers.

Online References:

Older scientific or horticultural names

Utricularia macrorhiza description by Thomas H. Kent, not updated.

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