If you want to avoid building a structure, I have also heard you can do the same thing with a 5 gallon bucket for fingerling potatoes. I haven't tried it yet, but the technique is on my list for this year

Five gallons really seems too small. I grew some Red Pontiacs in those 18-gallon blue rope-handled tubs from HD last fall and that worked great. But the cages are easy, too. Just take a 10-ft. section of 30" fence, hook the ends together for a 3-ft. circle, and put in 10" or so of shredded leaves or compost, and plant. As the stems grow up, just add more leaves, and potatoes will form on the new stolons. To harvest, just unhook the fence and paw through the medium for a payday crop. Then re-hook the cage and plant some late tomatoes or melons. The yield from six square feet is amazing. Misterbaby.

I can't thank you enough for the potato cage idea. I'd never heard of it, and it's just what I've been looking for.

I only have a 4' x 8' bed for potatoes, and am willing to do whatever it takes to maximize yield. Would I want to put a number of (20" by 20") boxes on the bed with one seed in each one, or can the cage idea be extended to a 4' x 8' bed. I believe I could sink pilings along the edge of the bed, and screw 2x6's to them along the sides of the whole bed as the bed builds up.

FWIW, the bed was dug down 2' last fall, sandy subsoil removed, and replaced with topsoil, 1.5 yd^3 of compost, 10 cu ft of peat, 1/2 yd^3 of leafmold and probably 1 yd^3 of eelgrass, all worked in to a depth of 2'. Bed's under a 6" layer of eelgrass mulch right now.
Our drainage is great (think beach) but I'm limited to ~6 hrs of sunlight from a tree which I don't dare take down, but would consider taking off some offending branches; that might bring me up to ~ 8 hrs of direct sunlight.
I have an inexhaustible supply of eelgrass, and could use that, compost or decent topsoil to fill up the bed.

Any comments or ideas would be very welcome. Thanks in advance.

There have been some long threads on the subject of potato-towers before. The single important conclusion was that one must be sure and use "late-season" varieties, vs early or mid-season. This is because only the late types will continuously set new tubers after the stems green. It isn't feasible to practice the cage, tower, stacking (call it whatever) method without greening the stems. The other varieties will not have increased yields and the extra effort will be wasted.

I see two different angles for high-yields from small spaces; both are well-known and discussed. First, direct high yields from a given plant requires all the factors be ample: sun, moisture, fertility. Any deficiency in those will be very noted because of the few plants or sq ft. Second, timing and stacking. No crop grows by itself, no area is used for one brief season. Even fruit trees can carry a few runner-beans, for example, or have potatoes under the south side as a ground cover.

I have an order of Russian fingerling coming from Johnny's and understand it's a late variety amenable to this technique. I'd appreciate any comments on whether it is indeed suitable for the cage method.

Hey, Josko! Glad you find the thread interesting. PN is spot on with the "two angles" advice. Sounds like you've got the tilth and drainage issues well in hand, but you'll do well to prune the shade-maker as heavily as possible. I can't speak to the Russian fingerling, but the technique should work fine for you as proposed provided that you can reach far enough to tend your plants. (You have to be able to add and pull up compost continuously around each subject without damaging adjacent plants, and they get quite bushy once underway.)

In the Memphis area, I get three flips per season from every square inch of garden; e.g., onions, then green beans, then mustard. Your 4x8 will produce more if you think companion and succession planting, though your clime may allow only two crops w/o protection.

Along this line, have you got your flower beds loaded? I fill mine with sweet potatoes and peppers, among others. Plants like these look great. Misterbaby.

i think the tower idea might work for sweet potatoes too. Can anyone confirm?