Interesting, as you can tell by looking at the map Kelly posted above, here in California water hyacinth is a highly invasive plant. So much so that in July of 2011 the California Department of Food and Agriculture released a South American bug (Megamelus Scutellaris aka the water hopper) as a biological control agent. Supposedly this bug feeds only on the water hyacinth.

JHAP
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"My mind is a raging torrent, flooded with rivulets of thought cascading into a waterfall of creative alternatives."
...Hedley Lamarr (that's Hedley not Hedy)