Try greening them before planting.

Concur. In my childhood, lots of folks planted fall potatoes after summer harvest (July). They simply left small potatoes in the row exposed to the sun untill the skins turned green and then planted them for the fall crop.

I just planted a bunch of old seed that I happened to have around. Testing out a story that I heard where traditionally in the Wisconsin region people planted their main storage crop on Independence Day. Seems incredible for a region with such a short growing season, so I've always wanted to test it.

Thanks! I'll give that greening method a try.

Yesterday I planted a handful of potatoes I'd had greening up since May, waiting for midsummer space to open up. I use the little reds for this because they are such willing producers under all kinds of conditions. In rainy years late blight will melt down the fall potatoes, which is a substantial risk in my area so I keep the planting small.

Thanks for the ideas on late plantings.
I just dug up a row of early red potatoes, only to find that the voles had eaten lots of them. They had also produced leafing green seed potatoes on their stems (maybe in response to the vole damage?) They are 60 day potatoes, so I'm excited about planting a bed of them again now. Good way to (hopefully) get my money's worth from the expensive early seed potatoes!