Water hyacinth vs. water lettuce vs. salvinia: floating invasive identification
Three free-floating invasives that show up in similar lakes and ponds across the southern United States. They look nothing alike close up but homeowners often lump them together.
| Attribute | Eichhornia crassipes | Pistia stratiotes | Salvinia molesta |
|---|---|---|---|
| Plant form | Free-floating rosette with bulbous petioles | Free-floating rosette resembling romaine lettuce | Free-floating fern, paired oval leaves |
| Leaves | Glossy, oval, thick | Thick, ribbed, fuzzy, light green | Green to brown, hairy, paired |
| Flowers | Showy lavender-purple with yellow blotch | Inconspicuous, hidden in the leaf base | None — reproduces by spores and fragmentation |
| Roots | Long feathery dark roots dangling below | Feathery dangling roots up to 12 inches | No true roots; submerged third leaf acts like a root |
| Diagnostic feature | Inflated bulbous petioles act as flotation | Fuzzy texture on the leaves | Egg-beater hairs on mature leaves (whisk-shaped tips) |
| Growth rate | Doubles every 8–12 days in warm water | Doubles weekly in summer | Doubles in 4–10 days |
| Range | Southeast US year-round; summer-only mid-Atlantic | Florida, Gulf Coast, lower Texas, lower Mississippi | Texas, Louisiana, parts of Florida, Hawaii |
| Treatment | Mechanical harvest, 2,4-D, glyphosate, weevil biocontrol | Mechanical harvest, 2,4-D, diquat | Salvinia weevil biocontrol, fluridone, mechanical harvest |
Frequently asked questions
Are these invasives illegal to own?
All three are federally listed noxious weeds. Possession, transport, or sale across state lines without a permit is illegal. Florida lists hyacinth, lettuce, and salvinia as Class I prohibited under FAC 5B-64.
Which is the worst?
Hyacinth is the most widespread and visible. Salvinia is the most aggressive doubling time. Lettuce is generally easier to control mechanically because its rosettes break apart on contact.
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