French Breakfast Radish grows quickly and has a decent bolt resistance. Seeds can be started in early Spring or Fall. They produce the most flavorful yields in cooler weather. Temperatures 70 degrees or above cause them to be more pungent. Harvest your French Breakfast Radish when small. Check to see if the root is ready for harvest by carefully digging around it to measure the diameter. Your radishes are at their peak flavor when roots are about one inch in diameter or smaller. As French Breakfast Radish enlarge, their flavor can become woody.