In my Zone 6b garden (frost dates May 10 and October 10), I grow bulb fennel twice a year. For the spring crop, I start seedlings indoors between March 25 and April 10. These are set out in early to mid-May, under cloches if needed for wind protection. The first planting is ready to harvest in early July. For the second planting, I start seeds indoors between June 25 and July 10, and try to get the seedlings in the ground by August 1. My fall bulb fennel matures in early October.