Do you know what kind? I'm assuming the "hardy hibiscus" (usually H. moscheutos)? Since hibiscus blooms on new growth, you can cut it to the ground (or maybe leave a stub so you know where it is). They are one of the last things to sprout in the garden since they are summer bloomers. Although this year, I noticed my mother's rose of sharon (H. syriacus - slightly different one from the hardy type) has already started sprouting! Guess it was the mild winter.