55 days. Flash is a dark green-leaved collard that has earned a reputation for its vigor, high uniformity, and impressive yields. The 16-23 inch, smooth, broad-leaved plants are very slow to bolt, offering longer, more dependable harvests. An excellent cutting green with a mild, sweet flavor, especially if exposed to a little frost. High in iron, calcium, potassium, phosphorus, and vitamins A, B, C, and E. Rapid regrowth after harvest.