You can skip fertilizing the first year because most potting soil already contains round fertilizer pellets added by the nurseries.

In the northern half of the country, you can regularly fertilize it once, in June, using 1 cup of manure, compost, cottonseed meal. You can also use a general purpose chemical fertilizer per label directions. One application per year is fine. In the lower half of the country, you can fertilize in May and June. Throughout the growing season, feel free to use weak fertilizers like coffee grounds, liquid seaweed and-or liquid fish. Stop all fertilizers around July to prevent tender new grwoth from getting zapped by early Fall frosts.

Amendments like a/s should be added anytime that the ground has not frozen. Apply them per label directions. The effect of a/s occurs slowly so you need to apply it per label directions until .... forever as failure to do so will make the soil go back to its original pH Level.

To counteract other problems, you can add blood meal (high in nitrogen) & manure (high in potash) at the same that you fertilize the hydrangea or in Spring (two or three weeks after your average date of last frost).

If the wilting epsidoe looks extreme, water immediately. Otherwise, test the soil moisture: insert a finger into the soil to a depth of 4". If the soil feels almost dry or dry then add 1/2 gallon of water to a newly planted small hydrangea. Otherwise check the next morning. If still wilted, water at the same rate.

Wilting should be reduced in future years but it never fully goes away in the summer months. It is a defense mechanism that reduces the amount of sun striking the leaf surface. This makes the leaf loose moisture more slowly but obviously looks bad. You can maintain 3-4" of mulch at all times to conserve moisture and you can also water early on days when the weather service has issued wind advisories.

Pretty good advice there but I feel a need to dispel some myths about fertilizers :-) First, you are not "feeding" the plant by fertilizing - plants manufacture their own food through the process of photosynthesis. At best, you are supplying nutrients necessary to that process that may be deficient or missing in your own soil. With most permanent landscape plants, there is very little need for any additional fertilization after planting - most soils contain everything the plants needs in relatively adequate levels. And if you mulch regularly, and especially with compost or composted manures, you are replacing what nutrients that might be used up and may never need to use any packaged fertilizers.

Plants that prefer acidic soils - like most hydrangeas - often do need a bit of an assist if the local soil is not sufficiently acidic. A number of nutrients can be bound up or unavailable to the plants unless the soil is adequately acidic. The cottonseed meal that Luis suggests is a natural acidifier but sulfur works equally well (but somewhat less rapidly). Also any blended fertilizer formulated for acid lovers (aka Rhododendron, Azalea and Camellia fertilizer) will contain acidifiers as well as those nutrients that are often lacking/deficient in less acidic soils. Because most soils are buffered to maintain a specific pH, it is difficult to permanently alter soil acidity. Changes will be temporary. You will need to keep monitoring it and reapplying acidifiers as necessary.

Also, fall is an ideal time to fertilizer any woody plant - it is the period of most active root growth and plants are best able to metabolize nutrients at this time. The myth of tender growth being damaged by fertilizing then is just that, a myth. Just avoid a high nitrogen fertilizer - it is excessive nitrogen that results in lush growth that is vulnerable to all sorts of damage.....not just early frosts. Any blended organic fertilizer will be sufficiently low in nitrogen and can be used without fear in fall. Although I have naturally acidic soil, I prefer to use an acid lovers fert sparingly at this time to ensure a sufficiently low pH and good blue flowers rather than risk aluminum sulfate. That is the only fertilizing I do with any hydrangeas (or any other acid lovers) other than mulching with compost and the early fall application ensures enough time to set proper color before bloom season.

And pay no attention to advice that cautions against watering everyday or on any other set schedule. Water when the plants need it. That may be daily the first season, especially in summer, or even more frequently. The plants will indicate when they require water but sometimes waiting for that sign is too late - check daily and test the soil down against the rootball with yor fingers. It should always be at least slightly damp(not wet)to the touch. More mature/well-established plants may not need very frequent watering but check the soil periodically as well.