Reporting
Your neighbor had kind

Your neighbor had kind intentions, however, potatoes exposed to sunlight turn green. Keeping tubers covered while they are growing prevents greening. The green patches will taste causes a bitter taste because the flesh contains a moderately toxic compound. When preparing potatoes, cut away any green areas and discard. 

Also, when the potatoes are dug up, the weather conditions are important or the potatoes could turn green which changes their flavor. It needs to be warm and dry (after a period of little or no rain). Cloudy days are even better. 

All in all, potatoes must be grown—and stored—and harvested—in darkness.