They are cool-weather grass, so they are best harvested in the spring or fall. If you live in a warm climate, you can also harvest them in the winter, by simply snipping off the leaves with a sharp knife or scissors and it is best to leave about an inch on top. They will regrow quickly, so you can harvest them multiple times per season. When storing chives, be sure to keep them in a cool, dark place. They can be stored in the refrigerator for around a week's time.