Sorry for the delay. My PC got infected and I have been unable to use it since mid-week last week. Looks like I am going to have to reformat the hard drive. Dimwits!
Fertilzing is an area where you do not have to worry about much if your soil is not defficient in minerals. I have forgotten to fertilize in some years with no impact to plant health or bloomage. Hydrangeas are not heavy feeders like roses so two applications of fertilizers will usually do here in the South (once in June in the North); for example, fertilize in April-May and June. Just stop fertilizing before July. A cup or half a cup of cottonseed meal should be good enough; or use manure or compost.
I add some amendments in April to acidify the soil and I add some weak fertilizers like coffee grounds as soon as they leaf out. Not much mind you. It depends on whether Starbucks has any when I stop by and if any are left by the time I get to the hydrangeas. I also re-apply acidifying amendments in the second half of summer some years, especially if I notice that the plants ask for it. Some years they do. Other years they do not. I try remember to do that again somewhere between June-August.
Believe it or not, I find winter a difficult time of the year to water since "the camellia incident". I tend to turn off the sprinkler in the winter when there is word of cold/freezing temperatures so the drip irrigation does not kick in. Well, I forgot to turn it back "on" and some time passed when we had no precipitation. One day I noticed a camellia bush whose leaves were starting to brown out. When I checked the soil, it was dry like a bone. When I checked the sprinkler, it was still "off". Oops!
Hydrangeas, because they are dormant and are not evergreen, cannot tell you if they need water during those dry winter times so I now check the camellias and azaleas for signs of leaving the drip irrigation turned off again. Ha! Oh meeeee....