I live in Northern Idaho and have trouble with very cold springs, in fact last year we were getting down in the low to mid 20's the 6th of July. This makes it tough to get a good start on plants before the heavy heat hits late July and early August which then causes most everything to bolt straight flowering.

Some things I have found easy ways to get by, instead of growing radishes I allow them to go to seed and I harvest baskets of radish seed pods which are every bit as good as radishes and far more abundant. But with lettuce, spinach and so many other plants I don't really get anything usable many seasons and while I am a gardening nut it has become quite frustrating over the last 2 decades living in this area.

I have been reading about hydroponics for years now and have always wanted to give it a try. I happen to have five large ponds here on my farm and I thought maybe I might be able to utilize them for growing plants. I had several thoughts occur to me on that.

1.) The water temperature in my ponds is far more stable than the air temperature, growing on the water might help to avoid late frost damage to my plants without a great deal of effort with plastics etc.

2.) If plants were to be grown on the water not only would the water protect from cold overnight lows (commonly in the 40's or even upper 30's in mid to late August), but that the water temp would help to keep the plants cooler and protect them from the high daytime temps in July and August keeping them from bolting.

3.) If I could grow plants on the water they could water themselves directly from the pond and avoid having to run sprinklers and timers etc.

4.) Growing on the ponds would also provide some protection from deer/elk and various other forms of wildlife that enjoy destroying what little I do manage to grow. Hopefully the moose would continue on through as they usually do and "not" be attracted to my ponds with the floating plants.

Some immediate problems... My ponds are full of large mouth bass and bullhead catfish, some of the bass are in the 24 to 26 inch length range and many of the catfish are in the 14 to 18 inch range and they would likely be eating any hanging roots.

I have pretty good sized ponds the one I want to experiment behind my house is about 90 feet diameter and about 14 feet deep somewhere around maybe 450K gallons or so. The water in my ponds even in mid summer tops out at maybe 62 to 65 degrees surface temp so it isn't exactly the warmest water and I have no idea what May or June temps might be, no one has ever been tempted to try and swim at that time of year... lol... My early water temps may be too cold to get any good growth hard to say without some experimentation and seeing what the conditions are.

My initial idea is..

I was going to cut up some 5 inch by 3/4 inch boards on the mill and then notch the ends so that I can slip two milk jug handles over each end of the wood boards. By attaching 4 boards together I will have 8 gallon jugs more if I notch deeper so the number is able to be changed easily. Eight gallon jugs will give about 70 pounds of buoyancy. I am expecting to float about 1,500 cubic inches of my soil mix which even fairly heavily laden with water would weigh in around 60 pounds allowing me to grow say several heads of lettuce.

I am hoping to get the right balance so that the raft will float with about 1/4 to 1/2 inch of the soil below water level the rest above so that the water has to wick up through the soil to water the plants. This will hopefully help to insulate the roots of the plants somewhat from the early cold water temps and allow them to warm with soil in daytime sunlight. I can adjust soil depth to control water saturation in the upper layers.

Plants that immediately came to mind that I would like to grow enjoy eating and that are cold tolerant were..

Spinach, lettuce, cabbage, chard, water cress, radish, arugula, beet, cilantro, kohlrabi, leek, and turnip. Any ideas on cool weather plants that might work for something like this?

I have it down to where it won't really cost me anything to experiment with this so I am out nothing but some time and thought if it doesn't work, but any ideas that might help my chances of success would be greatly appreciated.