Picture comingThick, glossy, heart-shaped floating leaves with a red spongy disc underneath and long white roots; forms dense surface mats.
Check your local laws. Australia (NSW): all Limnobium species are Prohibited Matter (illegal to deal in); not known in Australia. USA: on Washington State's Prohibited Plants/Quarantine List; listed as a state noxious weed in California (CDFA, as cited by USDA APHIS 2013). Native, unregulated in Florida. Not on the USDA Federal Noxious Weed List. Never throw it into ponds, rivers or drains.
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