the person at the greenhouse doesn't have a clue about anything. But the hyacinth and water lettuce wil both die anyway. They are tropical.
Leave your plants in the pond. Not in containers.

I am new to ponding (and Michigan) and since I had such a difficult time locating water hyacinth before mid-June...I am going to attempt to overwinter a few of my water hyacinth and my papyrus.
Now that I finally have sparkling clear water I don't to want to chance a repeat of the pea soup algea that took hold of my pond early this spring.
I have found a very informative site:
http://gardenline.usask.ca/yards/overwint.html
It's written by Garry Miller, a landscaper who specializes in aquatic gardeing and was provided as an extension service by the Extension Division and the Department of Horticulture Science, University of Saskatchewan.
The way I see it is I have nothing to lose :-)

deb- i overwinter my water hyacinth and lettuce in an aquarium over winter. the water is kept at 80 degrees with a heater and a flouresnt bulb for lighting. i add some aquarium plant fertilizer per instructions. they do just great!! i end up throwing them away all winter long just to keep the from overgrowing! i do use an airstone w/ airpump (cheap to buy ) to circulate the water

Paul

I live in ferndale Michigan

Trying to overwinter water hyacinths and lettuce is a long shot for most people. They need warm temps and lots of light.
I've managed to overwinter hyacinths in a plastic tub in front of a south window only to have mites attack them and kill them pretty quickly. A few ponders manage to overwinter them but its pretty tricky. Any of your other plants that are hardy varieties will be fine in the bottom of the pond where they won't freeze.
Several years back there was a person that potted water hyacinths in thin mud and placed them in her south facing sunroom and they did great. It just takes the right spot and it can be done.

Paul-
thanks for the info, looks like I'll be buying an aquarium before the first frost.
Not sure where Ferndale is...I'm still trying not to get lost here in the Portage/Kalamazoo/BattleCreek area, lol.

We're going to remove the last of the over grown shrubs from around the pond this weekend. I'm really looking forward to being able to see the pond without having to practically stand in it!
We must be doing something right...the 6 "little" survivor fish we inherited when we bought the house in March are now huge. We've also noticed several tiny, little black babies swimming around the past couple of weeks and two green frogs have moved in:-)
Not sure I'm keen on the frogs though...I pulled three dead ones out of the pond in May, ugh. Any ideas on how to discourage them from trying to hibernate in our hard plastic preformed pond?
One last question...where did you find the lettuce? I tried parrot feather but it didn't last long, our fish devoured it.

Thanks again for all of the advice...I just love this site.
Deborah

I had the most awful experience in my little water garden one year when I didn't put my warmer in over the winter. My fish had been eaten right before the winter so I did not put the warmer in thinking I would save some electric money and in the spring the frogs suffered the consequences. I use a trough warmer from one of the local feed stores and it works great to keep a hole open so the critters don't die from the ice cover...good luck.

Katherine

It is possible to overwinter and I did but had to discard many due to their invasive growth. I now add them to my compost as they are rich in nitrogen.