Baby arugula leaves can be harvested 24 days after planting, mature leaves in 35 days. Continually harvest the outer leaves to keep the plant small and prolong the growing period. Or, succession plant arugula every 2-3 weeks to enjoy baby greens throughout the season. Either way, arugula is best picked when the leavves are small and tender, as leaves tend to become bitter and woody as they become large. Left to grow in warm weather, arugula is quick to bolt. The white flowers and seeds pods that result are both edible. Save arugula seeds by allowing them to dry on the plant, but be sure to harvest the pods before they shatter and disperse, as arugula will readily reseed itself all over the place if allowed to do so.