It's mid-May, but my rose-of-sharon hasn't leafed out yet. Is it dead?

FAQ
Question: 

It's mid-May, but my rose-of-sharon hasn't leafed out yet. Is it dead?

Answer: 

The rose-of-sharon (Hibiscus syriacus) can be successfully grown in the southern half of Iowa. (It’s hardy in USDA Hardiness Zones 5 to 9.)  The rose-of-sharon leafs out late in spring.  In Iowa, plants may not leaf out until late May or early June.  Give the shrub a few more weeks.  If it hasn’t leafed out by mid-June, it’s probably dead.  Winter temperatures of -20 degrees Fahrenheit or lower can injure or destroy the shrub.