mulching ericaceous plants

Hi, can anyone tell me please should I be mulching my roddedenrons and hydrangers now with very well rotted leaf mulch, would this be benifical to these types of plants or harmfull, also can anyone recommend a slow release fertilsier for these type of plants many thanks    

Rhodos and hydrangreas are quite shallow rooted and adore anything that will keep their roots moist (besides regular watering  ) Every spring I simply add whatever fertilizer I have on hand all around the bushes as well as a good sprinkling of sulphur powder and evergreen needles if I can get any of the latter. Then I mulch with lots of shredded leaves (which I have abundance of) and some compost. I try to apply the mulch right after a heavy rain so that moisture stays in the soil as long as possible. Slow release fertilizer is good but I wouldn't go heavy on the first number (nitrogen).

Japanese hydrangeas don't seem to be as fussy as I have one in a difficult to reach corner, in heavy clay, and surrounded by shrub roses and monarda (bee balm). I've never yet watered or mulched it despite our bone dry summers here and it thrives. Unlike my English hydrangea which wilts if you even look at it