Without giving it much thought, this spring I decided to try growing potatoes in a box after reading a story in the Seattle Times.
It didn't work. From an initial planting of three pounds of seed potatoes I harvested one and a half pounds of potatoes. That's right, I went backwards. A far cry from the 100 lbs(!) or more mentioned in the article.
After swallowing my pride and setting aside the feeling that I was a fool for wanting to Believe, I came up with a few thoughts on why it didn't work.
The first might be that I planted the wrong variety, i.e. not late season, of potato. Inca Gold are a mid season potato; I've read that you should avoid early season varieties because they only set up one bunch of potatoes. While excavating the potato box, that seems to be what happened in my case. All the vines grew 12-16 inches, set up one cluster of potatoes, then no more. That's still only a partial explanation. I should have a lot more than 1.5 lbs from one "set" of potatoes.
One clue that things weren't going well was a dearth of flowers on the tops of the finished vines. Flowers are a sign that the tubers are setting up, I only remember seeing a couple in mid-August.
It was very cold this summer in Chicago this year, though I don't think that's the answer. I found a couple of slugs inside the potato box, but the potatoes, and vines, didn't look gnawed on. The plants looked healthy, suggesting they had enough water and fertilizer. I've grown tomatoes successfully on the same spot--in the ground, not in a vertical tower--in the past, so I think it gets enough sun. With so many variables, it's hard to know what went wrong.
Honestly, I'm at a loss. I was hoping to at least be able to figure out what happened. Maybe some of our readers will have a clue.
I plan on reusing the soil, a mixture of coir, peat, and vermiculite, in my several of my rooftop SIPs next year.
I'm not sure if I'll try growing potatoes in a box again. I'd like to try something more conventional, like growing them in containers.