Taiji wrote:... Some are actually getting up to about 15 inches high and real bushy.
Could I possible get a second potato crop in the same year from volunteer plants? That would be something. Maybe at least some small new potatoes! In this zone and at this elevation that would be unusual.
I tried this deliberately one year.
Purple potatoes are a common "miss" for my careful, spud digging. Really, I usually find them all since I dig out the entire bed to about 8" in the harvest. Don't find all the purples, however. They come back as the tiniest of plants and account for nothing by season's end.
Back to re-planting deliberately one year: Potato harvest starts in my garden in July with earliest variety. Yukon Gold is an early variety and I moved some tubers to another location and replanted. I'd talked briefly to an actual potato farmer about this and he said that he didn't think it would work. Advice from a Virginia gardener was that it would work. I don't live in Virginia ...
I didn't even see those plants emerge that year. It was a mild winter, which is becoming somewhat common here. Those potatoes showed up in the spring. They produced tubers but didn't do as well as that year's plants. I don't know why that was.
I'd hoped for 2 harvests in the same year from a quick maturing variety. It didn't work. The tubers must have had their own ideas on the process. Your 15" tall plants sound like you have a good chance in your garden. I think it's worth a try to deliberately try this in some environments and with some varieties. It would be helpful if several ag schools would take it on as a research project.
Make everything as simple as possible but not simpler. ~ Albert Einstein