Water plant that doesn’t go dormant in winter?

[KoiFan84]

I’m looking for a marginal water plant that has plenty of roots, can handle shade, and does not go dormant in the winter. Does anyone know of any that most importantly won’t go dormant in winter, or at least whose root system continues to help with water quality even when it is dormant? Thanks!

[*Ci*]

Depends on where you are located … can you supply that info?

[fly4koi]

Water Hyacinth (check your local laws), duckweed, water lettuce, moss ball, but depends largely on your USDA zone. If you can get carpet algae to grow or even just use string algae with manual control that'll work as well.

[KoiFan84]

Depends on where you are located … can you supply that info?

Question is for a friend in Augusta, GA I believe zone 8b. Right now he has a big raised canvas pool. He has a roof over it. So just sun for a very short time part of the day. I would prefer the plant doesn’t go dormant, but if it’s roots still suck up nutrients well during dormancy that’s fine too. I prefer marginals over non floating plants. Less chance for koi to tear them up. Thanks!

[*Ci*]

I’m in zone b and my yellow iris did not go completely dormant in winter (when I had it in a previous pond). Many leaves die back, but maybe about 1/3 remain green. It is, however, very invasive and every year I had to cut out great, heavy blocks of it, to keep it under control.
I also had mint growing in that pond, that stayed green all year. It started in a floating basket and then spread all over in a big floating mat (again, needed drastic control measures).

[gray cat]

I am in zone 8a. Sweet Flag Acorus, Horsetail Rush, Parrots Feather, and Floating Heart stay green for me all winter.