Anyone know what this is? Particularly interested in how large it grows....

Mouse's ear (Saururus cernuus) It has been grown emersed and will grow as big as you let it that way but is quite slow and small when grow submersed. Needs a lot of light to grow submersed. Those leaves wont grow much but it may throw new submersed growth.

Thanks! However this leads on to another (set of) observation(s)/ question(s):

I don't quite get the reference on this web site (the plant survey). It states that it grows from Canada to Liousiana; but the temperature range is only 18-24. It also seems to be listed as invasive on some US websites; which colaborates the range of US states and Canada. The temperature range seems as a result wrong?

Doesn't snow and freeze in the state of NY? Does it stop growing under those conditions? Maybe even dies back to its rhizomes? Is that what the plant survey is telling me?

If it was invasive in the US, would it be in danger of being invasive in NZ?

It grows quite happily outside in NZ.

Yes if it got going in the wild it could become a nuisance, but in the winter it dies right back, then starts the regrowth in the spring.

But I guess you knew that and wanted confirmation.

Alan 104

Yep, thanks...I think I had convinced myself that this was the case by the end of my last post. Thanks for the confirmation

It is usually grown emersed and sold to the shops that way because it grows a lot slower under water. The growth will slow down from about now and there will be less available. It was kept as an ornamental pot plant in England in Victorian times.