Plants: perennial, heterosporous herbs, free floating, with microspores and megaspores produced on the same plant, green, up to 30 cm long, 5 cm wide, mat-forming, mat to 2.5 cm thick (or much thicker, depending on local conditions such as water current, waves, etc.);roots absent;stems irregularly branched, pubescent.
Leaves: short petiolate, in whorls of three, two upper and one lower;upper leaves floating, photosynthetic, entire, elliptic-ovate to rounded, with a distinct midvein, aerolate, 0.7-3 cm long, to 1.8 cm wide, apices rounded to emarginate, the aerolae either fairly uniform in size throughout, or inner longer than outer;papillae apex split into several hairs that form a birdcage-like structure which traps an air bubble when submerged, creating a non-wettable upper surface;leaves often folded in half under crowded growth conditions;lower leaves subsessile or petiolate, with or without sporocarps attached, 1.5-2.0 cm long, to 0.5 cm wide, the petiole to 3 cm long, submersed, non-photosynthetic, finely divided into linear segments (feathery), segments appearing as and functioning as roots.
Sporocarps (when present): pubescent, sessile to long-stalked, globose to ovoid, rounded to apiculate at apex, either clustered at apex of submersed leaf or arising alternately in two rows down the length of the submersed leaf similar in size, sessile or stalked, in clusters or rows on lower leaves, the sporocarp wall a modified indusium;microsporocarps inconspicuous, globular, with an internal short column, the columns basal, bearing many microsporangia;microspores minute;megasporocarps inconspicuous, globular, with many megasporangia.
Microsporangia: stalked, with one massula (group of microspores);massulae with 64 microspores.
Megasporangia: sessile, with one megaspore;megaspores to 2 mm long.
Within the S. auriculata complex, to which S. molesta belongs, all of the species are very similar in their vegetative morphology. Therefore, reproductive structures should be used for identifying species within the complex whenever possible, though plants bearing sporocarps are rarely reported in the United States (Riefner and Smith, 2009). A comparison of species within the complex is provided in the section Similarities to Other Species/Conditions.
Related invasive species
- Salvinia molesta
Related Farm Practice
- Conditioning
- Rooting
- Groups
S. molesta is a free-floating aquatic plant native to south-eastern Brazil. It has been spread widely throughout the world during the past 50 years and is invasive in a variety of aquatic habitats, including lakes, rivers and rice paddies. Based on the environmental, economic and human health impacts, S. molesta ranks a close second behind water hyacinth on a list of the world's most noxious aquatic weeds. It has also been recently added onto the list of the world’s 100 most invasive species.