Your question is pretty vague & you haven't provided much info other than it's sunny & in back of your shed.

A pretty much foolproof perennial (that means it will come back in spring) & strikes me as appropriate for in back of a shed would be Rudbeckia 'Goldstrum'...or, commonly known as Black-eyed Susan. They are readily available, inexpensive, flower profusely over an extended time, birds love the seeds, and require little to no suplemental water in case you don't have water readily available behind the shed. If you leave the dead flower stems standing over the winter...the birds will love you. You will have seedlings come spring though which is either a negative or a positive depending on your desires.

Have fun & Welcome to Garden Web!
Tricia