Utricularia macrorhiza

Common Bladderwort

Common Bladderwort
Photo courtesy Wisconsin State Herbarium
and Douglas J. Buege

Flora, fauna, earth, and sky...
The natural history of the northwoods

Name:

• Utricularia, from the Latin, utricularius, "the master of a raft floated on bladders"
• macrorhiza, from the Greek, macros (macros), "long; tall, high, deep, far", and `riza (rhiza), "root; stem"; hence, in describing the root-less bladderwort, "large stem"
• Common name from its status as the most common Bladderwort of Europe and North America.
• Other common names include: Common Bladderpod, Greater Bladderwort (UK), Hooded Water Milfoil, Popweed, Vattenbläddra, Bläddreört, Blåsört, Mörkgul Vattenbläddra, Vattenblåsört (Swe), Storblærerod (Nor), Almindelig Blærerod (Dan), Isovesiherne (Fin), Gewöhnlicher Wasserschlauch (Ger), Közönséges rence (Hun), Lus nam Balgan Mòr (Gaelic), Harilik Vesihernes, Lihtne Vesihernes, Kalahernes, Vesipõis (Est), Bublinatka Obyèajná (Slovak)

Taxonomy:

• Kingdom Plantae, the Plants
  • Division Magnoliophyta, the Angiosperms (flowering plants)
    • Class Magnoliopsida, the Dicotyledons
    • Subclass Asteridae
      • Order Scrophulariales, the
        • Family Lentibulariaceae, the Bladderworts
          • Genus Utricularia, the Bladderworts
• Taxonomic Serial Number: 34456
• Also known as Utricularia vulgaris

Description:

• A submerged, free-floating aquatic perennial.
• Leaves alternate, lacy, complex, ¼"-2" long; repeatedly subdivided into segments of unequal length, decreasing in size to the final, thread-like segments. Carnivorous bladders are attached at regular intervals along the linear leaf segments, trapping and digesting tiny aquatic invertebrates.
• Stems sparsely branched; floating horizontally just below the water's surface, often forming large mats
• Bladders small, deflated, pear-shaped pouches. Not air-filled or used for floatation, they open abruptly when trigger hairs are disturbed, sucking in water and any hapless aquatic creature responsible for setting off the trap. Digestive enzymes and bacteria in the bladder then digest the prey for the nutritional use of the plant, a process typically taking 15 minutes to 2 hours, depending upon the size of the catch. When digestion is complete, special cells extract the nutrient-rich water from the bladder into the stem, thereby restoring the vaccuum and resetting the trap for its next victim. (If you lift a plant out of the water and up to your ear, you can sometimes hear the bladders' rapid intake of air, which gave rise to the name "popweed", sometimes applied to this plant).
• Roots absent
• Flowers bright yellow, perfect, irregular in form, rather resembling a snapdragon; usually 6-20 atop a stout, 2"-10" stalk. Lower lip ¼"-¾" long; upper lip of about equal size; spur about two thirds length of lower lip. Individual flower stalks curve downward when in fruit.
• Sepals 2-5
• Petals 5, united to form upper and lower lips
• Stamens 2
• Ovary superior (within blossom)
• Fruit a single chamber capsule, with central column bearing many seeds

Identification:

• Identifiable as a Bladderwort by its aquatic habitat and distinctive bladders
• Distinguished from other North Country bladderworts by:
  • Larger size
  • Densely subdivided leaves

Distribution:

• Circumboreal, south in North America to Florida, Texas, Arizona, and California.
• The most common Bladderwort of the Northern Hemisphere.

Habitat:

• Shallow water of lakes, ponds, peatlands, marshes, and rivers
• A voracious feeder on zooplankton, the presence of Bladderwort generally indicates an abundance of microscopic life, and a healthy aquatic environment.

Associates:

• Aquatic: Coontail (Ceratophyllum demersum), Duckweeds (Lemna minor, Lemna trisulca, Spirodela polyrhiza)
• Mammals: Occasionally eaten by muskrats, but not a preferred food.
• Birds: Occasionally eaten by ducks and other waterfowl, but not a preferred food.
• Invertebrates (as prey): Fairy Shrimp (Branchiopoda), Water Fleas (Cladocera), Copepods (Copepoda), Scuds (Amphipoda). Also preys on paramecia, rotifers, nematodes, and microscopic insect larvae.

History:

• In 1875 it was Charles Darwin himself who, along with two other biologists, finally established that the bladders of the Bladderworts were not for flotation, as had long been assumed, but were instead sophisticated traps for tiny animals.

Uses:

• With the other Bladderworts, a distinctive, if difficult, native for the water garden.

Reproduction:

• Sexually by seed
  • Flowers June-August
  • Insect pollinated
• Asexually by turions (winter buds), the most common method
  • Dense, starch-rich leaf masses form at tips of branches in late fall, dropping to the bottom and remaining dormant through the long winter.
  • Turions begin growing as spring water temperatures rise, absorbing air in their leaves to become buoyant.

Propagation:

• By seed

Cultivation:

• Hardy to USDA Zone 3 (average minimum annual temperature -40ºF)
• Not generally available commercially.

Links:

• Den Virtuella Floren, Naturhistoriska riksmuseet, Stockholm

Comments:

• The bladderworts are the only predatory aquatic plants in the US.