I heard that the potato will stop sending nutrients to the tubers if the stalks are bent. One of the most successful potato harvests I have ever seen was a large container grown project where he used several layers (think of a layer cake) of horizontal plastic fencing and t-posts at each corner to hold the horizontal fencing to keep the stalks from bending at all and support them as they grew. They were able to get an absolutely massive yield with that method although he was sick all summer and didn't care for them or water them at all. I am not sure that the container growing was as pivotal in the results as just keeping the stalks from bending over. I have container grown before and will try it again this spring as well as ground growing using his methods to keep the stalks upright. I think another often overlooked issue is either too much or too little phosphorus and potash in 10-10-10 fertilizer. I think 'balanced' fertilizers can present real problems for root crops since they don't need or want balanced inputs. You will always have too much of something and too little of the other. Also there is a time delay on phosphorus while it stays in the upper part of the soil, so you can apply phosphorus to increase tuber formation, but it takes 3 months to disperse into the soil, while nitrogen sinks like a stone through soil an becomes almost immediately bio-unavailable (or runs off into the environment via water). So if you are using 10-10-10 you are going to end up poisoning your plants in order to get one or another nutrients available in the correct quantity. Plus factor in the time delay to bioavailability. I think it is better to thoroughly prepare soil before you put your garden to bed in the winter than prepare it in the spring (actually I have revived some fruit trees that were very old and no longer producing by fall fertilizing; I got almost $700 worth of organic pears and even more than this in apples last year through fall fertilizing). I also heard (and studied it last year in my own garden) that potatoes grow between the seed potato and the surface. If you bury them deep you will increase yields as there is more space for them to grow above the seed potato. But if you plant them shallow, they have a very narrow area to make potatoes in, significantly reducing production. This means in container gardening you need to put them at the very bottom of a 1'-6" (0.45 meters) tall container to get a full yield. I tried this method last year and doubled my production. I was putting them very close to the surface before last year. Also, potatoes need cool roots and won't produce anything at all if their roots are too hot in the container during the summer. Afternoon/evening shade is a must in Southern US zones or other hot environments. Or you could insulate or shade the container.

- Christian