Storing potatoes

I staggered the planting of 16 containers of potatoes this year, one of the varieties I tried was "Swift". I have been lifting them during the summer, but up here near the Pennines, we can get very wet and cold autumns so I harvested whatever was left on the 15th September (they were planted at the end of April). To keep out the light, I stored them in cardboard boxes, packed with dry compost and kept in the garage.
They’ve been in for 10 weeks now and I’ve just opened one of the boxes, a number of them had sprouted, some up to 3 inches long.
Any ideas why this happened, and how do I prevent it in future?

 

Good evening John and welcome to the site. I would suggest the compost wasn`t as dry as you thought. As long as the spuds aren`t soft use them up.

 

Thanks Dai. I think that may be possible. We're certainly going to use them all, I just rubbed the sprouts off and you'd be none the wiser.

 

Now that'd be bonus if I could get sprouts growing on the potatoes. Two crops in one eh! I'd make a fortune.

 

Its the warm weather too

 

Thanks guys. Grateful for the advice

 

Swift are a first early and are ready to harvest from 8 weeks, planted in April..ready to lift in June. Mine where planted in March, lifted in May...none left in June..

Steve...