This spring I planted German Butterball potatoes in six plastic buckets. There have been reports of incredible yields from mounding potatoes exceptionally well. Claims of one hundred pounds harvested per pound of seed potato have been rumored. That kind of yield seemed fantastical to me, and other apparently rigorous scientific reports contradict such claims. Still, I wanted to try the experiment of potato mounding for improved yields for myself. I decided to trial late season potatoes, and each of the six buckets got just one seed potato each. I weighed the six seed potatoes together before planting, but not until I'd planted the fourth seed potato did I think to weigh the individual pieces. So I marked the weight of the last two seed potatoes on the buckets they went into.
First, a little background on what I might have expected from "normal" potato planting in terms of harvest yields. I'm told that a good commercial potato grower expects to see a 5x-8x return on each pound of seed potato he or she plants. In other words, plant a pound of potatoes, and you're doing well if you get anywhere from 5 to 8 pounds at harvest.
I planted my six buckets with just under a pound of seed potatoes. To be precise, it was 15.6 ounces of seed which had lost some moisture and begun to sprout (as is recommended for planting potatoes). As the plants grew up inside the bucket, I added more dirt to leave about 5"-6"of growth above the soil line until the buckets were entirely full. As bad luck would have it, spring this year was exceptionally wet. We got hit with late blight on our potato plants in early August, and soon after on our tomato plants as well. All was not lost however with the potatoes. As was recommended to me by our Agricultural Extension agent, I cut the potato plants down to the ground and destroyed them, but left the tubers undisturbed in the soil. If we waited at least a few weeks to harvest, he gave us even chances on harvesting a blight-free crop of the tubers. We followed his excellent advice and so far have seen no evidence of the blight on the spuds themselves.
I'm getting to the yields on our six bucket-grown potato plants in just a moment, but I want to emphasize that the need to cut down the potato plants earlier than normal in the season almost certainly means that our yields were smaller than they otherwise would have been. From the 15.6 ounces of seed planted in the six buckets, I harvested 8 pounds, 8.9 ounces of potatoes on Sunday. That's an 8.8x return, placing the potato bucket harvest slightly above the high end of average commercial yields. In other words, the potato bucket plantings did great, in spite of the blight.
One of the two buckets for which I had the individual seed potato weight produced the lowest yield, probably because it was the one bucket in which I found a few rotten potatoes. That bucket received a 2.3 ounce seed potato, and yielded 1 pound, 4.1 ounces (or 8.7x). The other bucket for which I recorded the seed potato weight (2.1 ounces) yielded 1 pound, 13.5 ounces, or an incredible 14x return. The four buckets for which I did not record individual seed potato weights used 11.2 ounces of seed potato between them, and yielded 6 pounds, 8.2 ounces, or a return of 9.3x collectively. Given that we got hit with late blight, I feel that we could expect a slightly better return in a more average year.
Most of these containers were food-grade plastic, 5-gallon buckets. One was a little smaller than the rest, however this did not seem to make much difference to the quantity of potatoes from that bucket. Although I was not exceptionally rigorous about examining this, it seemed to me that all of the tubers were produced along one part of the plant at the lowest level of the bucket, right around where the original seed potato was placed. The mounding may still have helped these plants produce more by providing additional nutrients. But it did not appear to me that additional sets of tubers were produced higher along the stem as the plant grew upwards.
Although the yields I saw with the potato buckets were nowhere near the fabulous yields ascribed to potato towers, I think the concept has other merits worth considering. For one thing I should note that the potatoes we had in buckets were situated right next to the first group of in-ground potatoes to show late blight, and yet they were the last of all our plants to show any evidence of blight. I believe that the better-than-in-ground drainage in the buckets helped the plants, as did the higher elevation of their stems and leaves, which allowed for better air circulation. Blight strikes where there is enough moisture to support the fungal infestation, and these bucket-grown plants were drier than those in the ground. In fact, I had to water these plants quite a bit, whereas rainfall alone took care of the potatoes in the ground once they were established.
Another benefit of growing the potatoes in buckets was the ease of harvest. All that was necessary was to dump each bucket into a wheelbarrow. Inevitably when digging for potatoes in the ground, I spear a few spuds with my pitchfork. That never happened with the potato buckets. Also, there's very little chance that I missed any potatoes from the buckets. Clearly I missed a few potatoes during last year's harvest, because I had a few volunteer potato plants where they weren't especially wanted in the garden this spring. Though the buckets were heavy, the harvest from potato buckets was much easier than the digging we'll need to do to harvest the rest of our potatoes. In terms of yield per square foot of garden space, I honestly cannot say whether the buckets are superior to growing potatoes in the ground. But the harvest was very easy indeed.
I know I've seen a picture, somewhere, of planters stacked in a pyramid shape, with plants growing out of each one. (I've you've seen this picture whilst poking around the intertubes, please point us there in the comments.) Each container on the second course straddles at least two containers on the first level, leaving enough room for the plants in the first course to grow. While I wouldn't want to build a very high pyramid with 5-gallon buckets, I think it might be worth trying. Anything above 3 courses high would be too difficult to fill in gradually, water, or remove for harvesting. But the pyramid idea would help to maximize the yield from a given area of garden space. And it could be grown on a driveway or some other space not otherwise useful for food production.
Rob over at One Straw has been experimenting this year with 2'x2' potato towers. He should be harvesting them fairly soon. I look forward to seeing what we can learn from his results this year.