Cabomba caroliniana A. Gray

Carolina Water Shield, Fanwort

Cabomba caroliniana plant

Family - Cabombaceae

Cabomba_caroliniana_plant2Plant.

Stem - Mostly submerged, inconspicuously hairy when young.

Cabomba_caroliniana_stemStem.

Leaves - Strongly dimorphic, with emergent leaves only present at flowering. Submerged leaves opposite, petiolate, to 4 cm long and broad, fan-shaped, palmately divided into 5-7 parts, each of these further divided into narrow, threadlike segments. Emergent leaves alternate, long-petiolate, peltate, with blades to 2 cm long, entire, roughly oblong but often shallowly notched.

Cabomba_caroliniana_leaves2Submerged leaves.

Cabomba_caroliniana_leaves

Cabomba_caroliniana_leaves3Emergent leaves.

Flowers - Stalked, held just above the water, the stalk bending to become submerged as the fruits develop. Sepals 3, 5-10 mm long, petaloid, elliptic to obovate, white. Petals 3, 5-10 mm long, elliptic to obovate, sagittate toward the base and thus appearing short-stalked, white with the basal auricles each with a yellow nectary. Stamens 6. Pistils 2-4, the stigma capitate.

Cabomba_caroliniana_flower2Flower.

Cabomba_caroliniana_flower

Cabomba_caroliniana_flower3

Flowering - May - September.

Habitat - Submerged aquatic in ponds, sloughs, swamps, ditches.

Origin - Native to the U.S.

Other info. - This attractive aquatic species can produce large numbers of small white flowers at the surface of still waters, while most of the plant remains submerged. The plant is easily identified by its flowers and the dimorphic leaves. The sepals and petals are similar, collectively forming a six parted perianth. C. caroliniana provides good cover for fish and other aquatic invertebrates, and is commonly grown as an ornamental for aquarium use. This use has led to its accidental escape and introduction at some sites beyond its natural range.

C. caroliniana could be confused with species of Ceratophyllum or Ranunculus aquatilis, which also have dissected, fan-shaped leaves. However, the leaf arrangement on these latter species is alternate.

Missouri populations of this species are assignable to var. caroliniana.

Photographs taken at Duck Creek Conservation Area, 8-26-2015 (SRTurner).



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