".........growing in the same hardiness zone you garden in, be very wary
> of introducing it to your garden. Colder zones might be safe........."
>
That's right, but plants can show a surprising
adaptability. Here in Argentina, Iris pseudacorus, atlhough not a
bualb, a cold climate species, has invaded the subtropical wetlands
where it chokes all other forms of vegetation with a mat of rhizomes
and is moving south into cooler regions. Besides fulminant vegetative
reproduction it sets plenty of corky seed that floats around and with
the rains sail away to anchor in new locations to be colonized.
Catastrophic.
Some plants are thugs no matter what. Not only does Iris pseudacorus
disperse by freshwater, it is also at least moderately saltwater
tolerant. In my area, it comes down the Columbia River and out to the
ocean beaches, along the beaches, where we find seed pods and seeds
regularly. So far, no demonstrated spread to other estuaries, but
it's a matter of time. Thankfully, it does not establish on the ocean
beaches; it needs a fresher (brackish) situation to grow.
Kathleen