Salvinia

Scientific name

Salvinia Ség.

Common names

water fern, water spangles

Family

Salviniaceae

Could be confused with

Phyllanthus

Native distribution

tropical Asia and South America

Species commonly cultivated

Salvinia auriculata Aubl. (tropical Central and South America)

S. cucullata Bory (Asia)

S. molesta D.S. Mitch. (Brazil)

S. natans (L.) All. (tropical Asia)

S. oblongifolia Mart.

S. rotundifolia Willd. (S. minima Baker) (tropical America)

U.S. Federal Noxious Weed: Salvinia auriculata complex

Identification: Salvinia auriculata complex is a group of closely related neotropical species that is distinguished by the shared feature of eggbeater type hairs. The members include S. auriculata Aubl., S. biloba Raddi, S. herzogii de la Sota, and S. molesta. Although subtle vegetative differences have been found among members of this complex, sporocarps are generally needed to tell the species apart.

Adventive distribution

almost cosmopolitan through introductions of various species

Weed status

Very serious environmental weeds. Salvinia molesta is considered one of the world's most troublesome aquatic weeds. Members of the S. auriculata complex are aquatic weeds on the U.S. federal noxious weed list.

Habit

free-floating, often forming thick mats

Brief description

Perennial water fern. Stem horizontal, floating, irregularly forked, lacking true roots. Leaves in whorls of 3, appearing paired; 2 leaves floating and photosynthetic, orbicular to oblong, covered with complex, unwettable hairs (open or closed at tips) on adaxial surface; third leaf hanging down below water surface, filamentous, resembling roots, not photosynthetic. Sporocarps borne on modified segments of submerged leaves, as chains, hanging clusters or rows. Prothalli develop inside floating spores. Dispersal commonly by stem fragments.

Natural habitat

common in still waters in tropical regions

Additional comments

Salvinia is a genus of ca. 12 species. Fronds appear to be paired, but are actually whorled. Two floating leaves are ovoid and photosynthetic while a third leaf is root-like and hangs below in the water column. Sporocarps are produced as a hanging cluster or in rows in the water column. Identification of members of the S. auriculata complex is based on the presence of 'bird-cage' or 'baby-rattle' shaped hairs on the upper surface of floating leaves. Other Salvinia species have the terminal hairs (or papillae) separated at the apex. Growth rates and biomass production are influenced greatly by nutrient levels in the water column.