Hi, 

This does appear to be a severe case of winterburn. We are seeing this regularly this year, especially with board leaf sensitive evergreens like gardenia. The weather patterns this year, mild weather with cold snaps, can be a common cause of the browning leaves. 

Although outright cold may not have gone beyond the plant's tolerances, a relatively rapid drop in temperature may have, thus causing the winterburn.

It is too early to tell if significant branch dieback occurred,  so we recommend not trimming it yet. You should wait until late spring to see if the shrub produces new foliage and sheds the damaged leaves, then any leafless or dead branches can be trimmed off. 

Hopefully the weather starts to even out and warmer days are ahead! 

-Emily