Q.If broccoli is a biennial what fall care does it need?
Does the plant die back to the ground? Should I cut it back? Do I cover with mulch? If so, what kind of mulch? After the second growing season can I plant new broccoli plants in the same part of the garden?

Certified GKH Gardening Expert
Broccoli is a biennial similar to how a carrot is a biennial. In order to obtain seeds, you must sacrifice the edible portions of the plant and only harvest the seeds after the second year.
If you wish to eat the broccoli, and not collect its seed, then it must be treated as an annual. This article will help you to grow broccoli: https://www.gardeningknowhow.com/edible/vegetables/broccoli/how-to-grow-broccoli.htm