Pond Boss Forums AQUATIC VEGETATION Balance of plants in the environment Floating Island/Wetland

Yeah John I plan on taking photo's now that you guys have gotten me curious.
I think if there's one plant on that island that could grow without soil it would be the Cattail, they could thrive on a bowling ball.
That's another good reason to put in artificial cover like the garland I have on it, I've seen small GSH around the edges and the island is over 8ft. of water where the trout like to be.

Bob Lusk has a floating island at the end of the pier on the pond at LL2. IIRC it's been in the pond for a number of years. I wonder if he knows what the root system under the island looks like?

I do know that aquatic iris survive well growing in 1/2"-3" sized rocks submerged in water. I know they grow bullrush and iris in baskets with just gravel/rocks in water. The rocks I think are just to hold the plant upright and in place. Cattails and numerous other wetland plants tolerant of anoxic soil conditions would also probably grow just water. The neighbor has a greenhouse where he raises hydroponic lettuce and the root mass gets to be 12"-16" long from mature lettuce roots growing in the dark with just water around it.

Bill do you know if your neighbor's lettuce is growing in water that has been filtered in his hydroponics set up? Also I have read that a growing medium even like coarse rocks will collect the particles and let them break them down so the nutrients can be used by the roots.

Adirondack I have one of those cheap underwater camera that I was going to use to take pictures last year under my raft of the one plant root, and to see if minnows were feeding off the bottom of the raft, and if fat head minnow were spawning on the underside, but the water quality with the tannin I have didn't seem like a good idea. But the one flowering plant I did have set up with the roots dangling so I could pull the cup out periodically and inspect the roots. That plant at first did grow just like the others and it's long dangling roots were white. Then in a few weeks the growth slowed down and started to die and the roots turned black. Later I inspected the plant and the roots completely rotted off.

Coir is a good option and it is organic. Paul Kay of Rogue Water came up with something he calls a "botanical burrito". You can roll some inert media like lava rock or expanded clay in a bit of coir (not too dense of coir for this application) and maybe a wee bit of compost (i agree with posters that the nutrients in the water should be sufficient for growth, but a head start wouldn't hurt the plants...still, you don't want to add nutrients to the water if they are a pollutant that you'd like to remove from the water).
Roll about four of these up like large burritos and poke holes in their tops to insert bare-root native sedges, rushes, or whatever wetland plants you like. Then lay about four "burritos" in a standard nursery flat. (Be sure they get saturated when deployed!) Paul floats these in a PVC frame that provides adequate flotation. (He says that it is important to get the dimensions of the frame very exact to hold the flats securely.) Other frame and floatation options could be considered. As an experiment, I successfully grew some plants in a burlap sack filled with nothing but dried blackberry canes and empty water bottles (almost free material) that I floated in a creek.
You might look atnorth fork natives, wetland sod to get an idea about how little substrate wetland plants need to thrive.
I know I haven't added much about building the floating structure (many experiments swirl in my head!) but hopefully these materials and methods help stimulate some ideas...good luck!

Here's the rice-sack planter I mentioned in my post. It's planted with Carex obnupta and Juncus sp. The tree is an Oregon Ash cutting -- my "tree bobber" experiment. I have a bit of video of some baby fish hanging out by the roots shortly after I set it in the creek; they seem to like it. Also, the plants (Carex glauca) in the other pictures were grown in a water treatment tank, the Eco-Reactor at the Oregon Garden, which is circulated with an "air-lift" system. Try looking up John Todd (toddecological?) to find info on that sort of system.

Really inspiring thread here. Beautiful stuff AP, and others.

I have wanted to float an island to grow some lettuce during the heat of the summer when it just suffers in the garden. Curious to hear more from Bill about the practicality of that idea.

I have a large coir mat that I convinced the wife to sacrifice for a floating lettuce island. I was thinking to build a floating framework from 1 1/2 inch ABS pipe, lay 1/2 inch plastic mesh over that, layer of newspaper, then the 2" thick coir mat, and finally a little potting soil for the plants to germinate in.
Is there something I am overlooking in this plan?

cheers fellas-

During June July Aug the greenhouse owner uses a special strain of bib lettuce that tolerates higher temperatures in the greenhouse. Water to each row of the lettuce (abt 16 heads) is supplied by a constant flow of water from a small diameter tube. Seed sprouts in a foam block and then each block is inserted into a hole of a 3"-4"wide x 10ft long growing "trays". Water from tybe drains through the tray and exits the end and then is recycled.

I still haven't replanted my island yet this spring. Turtles and frogs both share it. The turtles like to lay on the fake foam rocks while the bullfrogs seem to like the moist dirt so I am deciding wether to leave it like it is or to plant something.

Bill is right that plant selection is important to having a successful floating island. Wetland plants are most suitable for creating extensive root systems in water column because they are built to tolerate low oxygen conditions -- they have aerenchyma (hollow) tissues that allow for gas exchange throughout the plant. Lettuce and other likely food plants aren’t tolerant of saturated conditions like wetland plants are and I think root dieback would be predictable without some method of aeration. System and plant choices are going to be determined by your objectives.

I like John’s foam island and think it looks pretty cool. It looks like he was able to get some petunias to do well in it and it turned into a decent turtle hang-out. That design stays moist by wicking and infiltration of water, but the roots are probably well separated from submergence. It’s a really different approach with different possibilities for plant choice, aesthetics, etc. than a typical floating wetland. Adirondack’s planter probably does have a fair amount of roots under water (haven’t seen pictures) because of plant choice and design differences. If you want to grow lettuce in something like adirondack's planter (I like the plastic fencing idea a lot!), or in what you (adam) described, aeration would probably be a big help.

I think the filtration John refers to above may have more to do with the microbiology that breaks down ammonia than with filtering particulates. I looked at the post he linked to about the lettuce growing experiment and I’m not 100% convinced of the conclusions there. (I don’t know much about aquaponics (yet!) besides the fact that they usually use circulation systems, so I had to research the filtration aspect of it. Here's a decent article that seems to stress importance of “surface area” for microbial communities in aquaponics.)

The explanation of the problem in the lettuce experiment says that the roots weren’t getting enough oxygen because the solids (fish poo) were coating them. Solids probably do play a role in limiting oxygen to the roots, but I’d guess the dead roots in that trial just drowned as much as anything. If the water is too static, it’s not going to be as oxygenated as a re-circulating aquaponic system (RAS) would be. I wonder if aeration would be enough to overcome that root “coating” problem? I’d try experimenting by running a few feet of ¼” soaker hose (or and airstone) under one of those floating trays of lettuce, hook it to an (even dinky aquarium) air pump, and see if the roots and growth come out any different before I’d conclude that filtration is the main/only problem there. I could be wrong, but all the aeroponic, auquaponic, and hydroponic systems for horticultural products I’ve seen use some form of aeration and I think not having it was the biggest limiting factor for that experiment.

In any case, whether you are growing lettuce or wetland plants, floating plants and the associated biofilms on their roots are going to be more successful with aeration. Without it, you’re gonna have to adjust your plans and/or your expectations.

Phytomike you have given the best overall explanation of how different kinds of plants grow in water environments that I have seen. Thanks for putting it all together and making sense of it.