I started this as a reply to FarmetteReport but realized it’s probably useful for others too – so here goes:

I can tell you about how our sweet potatoes did last year, which was our first time trying them. They did great! We got some advice from the Cornell Coop Extension – you can contact them (google their Growline) and they’ll send you some pamphlets about growing sweet potatoes in cooler climates.

In Ithaca (zone 5a) I recall they were able to get 300 pounds of potatoes per 100 feet of row (3 pounds per plant). We got about 200, not too shabby. There seem to be two key steps:

1. Make mounded rows, about 18" tall

2. Cover the rows in black plastic, preferably a few weeks before you plant. This warms up the soil.

The plastic and the mounds keep the plants warm all season long. For the plastic we used black garbage bags, cut open. We ordered slips from Gurney’s, varieties “Beauregard” (100 days) and “Georgia Jet” (90 days). Only the shorter-season varieties will grow in our climate, and these two worked great for us. There are longer-season ones that southern gardeners like. You have to look at the days-to-maturity. I can definitely recommend these two. For this year we just ordered Beauregard since we liked the flavor so much. They were both good.

So you plant slips (not tubers) around the same time you put out tomatoes – cut a hole in the black plastic, put the slip in and of course make sure the plastic is weighted down with rocks. The plastic also keeps the weeds away during the summer, so they are low maintenance. I don’t remember any pests, but we fenced to keep deer away.

You want to harvest right before the first frost. Actually we harvested the morning after the first frost – the plants had frost damage AND the deer had broken down the fence the same night and they ate all the leaves! If the plants frost and you don’t harvest, the tubers can be damaged. So you can wait until the frost hits but you have to harvest right away.

To harvest, we clipped off any remaining stems/leaves to make it easy to pull off the black plastic. Then I think we used a potato fork (it looks like a pitchfork) to gently break up the mounds. Each plant has a cluster of potatoes hanging from its roots. Some tubers are big but most were skinny. Put them into bags or boxes with the dirt still on.

You have to let the tubers “cure” for about a month. We had them in cardboard boxes in our house. (You want the temperature and humidity to be as warm as you can manage – there is info on this if you google it, I don’t remember the details). But don’t eat them right away, they aren’t ready yet!

After that month of storage, they’re ready to eat. We found them similar in taste and texture to store-bought sweet potatoes (though of course we liked ours better!) Considering you can buy them for about 99 cents a pound, ours were cheaper, too – I think we spent $100 (including fencing, etc) for a crop of 200 pounds. *