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Invasive Species Sheet - Brazilian Water-weed

Invasive Species Identification Sheet

Brazilian Water-weed (Egeria densa Planchon)

Alternate Latin Names: Elodea densa (Planch.) Caspary; Anacharis densa (Planch.)

Victorin; Philotria densa (Planch.) Small & St. John

Alternate Common Names: Dense Waterweed; Anacharis; Leafy Elodea; Egeria
- underwater plant with leaves in whorls of 4-5 most commonly (some 3-6[-8])
- stems usually 1-2 feet long
- middle and upper leaves 1/2"-1 1/2" long and up to 1/4" wide
- very fine teeth on leaf edges require a hand lens to see
- vegetative reproduction is by stolons (creeping stems) and stem fragments
- flowers have 3 white petals and 3 green sepals half the length of the petals
- some petals (on male flowers) may be up to 1/2" long

The larger, leafier Brazilian Water-weed may be confused with the native waterweeds (Elodea Michx.) or the nonnative Hydrilla (Hydrilla verticillata (L.f.) Royle). Brazilian Water-weed lacks turions while the native Waterweeds have stem turions (dense, dark green leafy growing tips with the nodes very close together). Hydrilla has both stem turions and tuberlike turions that grow underground in the rooting zone. Leaves typically longer than 3/4" distinguish Brazilian Water-weed from the native Water-weeds and Hydrilla. In addition, the need of a hand lens to see teeth on leaf margins distinguishes Brazilian Water-weed (and the native Water-weeds as well) from Hydrilla which has teeth that may be seen without a hand lens (if one looks closely).

Brazilian Water-weed is a popular aquarium plant that can create dense mats in the wild. Freezing water causes it to die back, but it has survived in the wild in New England.