We have a number of hydrangeas, all happy. Our largest and oldest one started fine this year; there was new growth on the stocks that we did not cut off last year (should we have?). We had a frost which killed the new growth. We later cut them off. (should we have?). Now there is just a couple of spots in the mulch that a few leaves are more or less growing. What did we do wrong? We put more mulch on than usual last winter, could it have been too much? Should we have taken most of it off this spring? Is there anything we can do to help?This plant is about 5 years old and was getting bigger each year. I don't know what kind it is (pink).
why is my hydrangea sick?
If you wound up having to cut off stuff that got frost damage, it sounds like the problem may be that you pulled the mulch off too early--you shouldn't pull the mulch off until there's no chance of frost anymore (and if you get a sneaky super late frost, you should see if you can find some frost cloth or something to cover the plant up with temporarily). If the plant got hit hard by a late frost/freeze, it may take it a while to recover. As long as the little bit of new growth that's there looks healthy there's not much you can do besides sit back and wait, and make sure you give it plenty of protection next winter and don't pull the mulch off too early.
As far as cutting it back, when there's frost damage it's typically a good idea to leave the frost damaged parts on for a little while just in case they weren't really dead, often things will look bad but then if you give it a little time it may leaf out again. You should also never prune off the damaged parts until all chance of another frost is gone--the damaged parts can help protect the more tender growth underneath from subsequent frosts, so if you prune it off too quick then the next layer down on the plant can get damaged in the next frost. Once all danger of frost is past though and you're sure that part's dead and isn't going to leaf out again though there's nothing wrong with pruning it out, otherwise it'll just sit there looking like ugly dead sticks!