Good quality Brussels sprouts are firm, compact, and vivid green. They should be free of yellowed or wilted leaves and should not be puffy or soft in texture. Avoid those that have perforations in their leaves as this may indicate that they have aphids residing within. If Brussels sprouts are sold individually, choose those of equal size to ensure that they will cook evenly. Brussels sprouts are available year round, but their peak growing period is from autumn until early spring.