Pond advice

My property includes two fairly large ponds (the larger of the two is probably about 1/3 acre in surface area, the smaller is probably 1/4 of that). Neither of them seem particularly healthy, although I don't know how to quantify or describe this. I have been researching plants that I could introduce to the ponds to increase overall health, increase biodiversity, reduce evaporation, and produce harvestable resources. The conundrum I am facing is that it seems almost every aquatic plant out there comes with a warning that it tends to overgrow and can be invasive, and there seems to be no way to experiment and learn, since once introduce there will be no realistic way to eradicate them. This is especially a concern for the larger pond, as the overflow continues down into my neighbor's property. Plants I'm considering most at the moment include: duckweed, waterfern (azolla), hornwort, cattail, and lotus. Thoughts? Opinions? Experiences?

Another issue I'm facing with my ponds is that both of them have rather steep banks. One of them has a vertical cliff face as one of it's banks (it's artificial, of course). This is a great source of erosion. In some places I've planted willow to control the erosion, but especially on this cliff face there are extra challenges: first, the substance is basically just deep clay, the kind of stuff that nothing wants to grow in, and second anything planted on the lower sections of this cliff face would be fully submerged for much of the year. Any advice appreciated.

Thanks.

Hi Mr. Finch, Good to meet you.

I have no real experience with aquatic plant species except duckweed. And just to give you some perspective on it, It can double in numbers very quickly. It even comes back after being frozen solid...somehow. The only way I know these things is an Egret brought some in to my pond last year. It's easy to remove with a pool net or something similar and makes great compost.
Some fish also feed on it.
You mentioned something for food.
I have a little project that turned out quite well. I took 1 of those foam boards 1" thick and drilled holes in it 3"uniform from 1 end to the other 4 rows, perfect for a 4" pot to sit down in reach the water and not fall through. I grew so many greens so fast I couldn't eat them all. It will help with your Ph and Nitrates in the water and provide cover for the fish. Where ever it is it will block out the sun and slow underwater vegetation in that area. How many is up to you, what you plant in them is up to you.

I don't really know about your area and the substrate/structure of the soil around your ponds ,but I would be careful planting trees near the banks to control erosion if you have an evaporation problem that actually might be a leaky pond. If the substrate of the soil goes from clay to sand, especially if the ponds where made in this fashion. Planting trees too close could cause "holes" or punctures in the retention layer of clay and then you will not only have an evaporation problem but a Leaking problem too. Before you continue please try to find out or investigate. I have seen ponds go dry because of this.

I would look into partially/fully aquatic grasses for the erosion.

I'm sure you will get some other great responses in this forum.

Have a good one!

It seems like almost every plant will spread and spread eventually. In other words, nothing stays in nice neat groups where we'd like it to be!

Of the plants you mention, I have experience with two: duckweed and hornwort. Yes, they do keep growing and spreading. We keep them manageable by using them as feed for our poultry. The duckweed is easy to skim out with a strainer and we put it in pans of water in the poultry yard. Chickens, Muscovys, and turkeys all love it. The hornwort, we pull out with a rake. My  husband chops it up some before giving it to them, but I've just dumped whole clumps into our mini duck ponds in the chicken yard.

My water lilies and pickerel patches are spreading, but I chose them because they are edible. The cattails and lotus you mention are edible as well. I think by choosing edible water plants, it's easier to keep them manageable because they can be harvested for food, like other crops. They're just perennial water garden crops.

Duckweed makes good mulch, and I suspect hornwort would too. All of them can add to a compost pile, so there's another good use for anyone wanting to keep them manageable.