Several leaf-spotting pathogens can infect Bigleaf Hydrangea (Hydrangea macrophylla, the type in the photos), and we see many submissions this time of year about this issue. Your plant looks pretty typical, if it's any consolation. Fortunately, these infections are not threatening to the overall health of the plant, even though they can be an eyesore.

Fungicides aren't warranted, nor will they be of much use this late into the disease cycle; they are preventative measures only, not curative. When the hydrangea leaves shed this autumn, you can rake them up and dispose of them (only compost if you have a "hot" compost pile; passive composting may not kill their spores). This is not a foolproof means of minimizing disease risk for the following year, since spores can always blow-in on the wind or flow into the area in storm deluges (and the fungi themselves are pretty ubiquitous), but collecting its fallen leaves wouldn't hurt since it does remove some spores from the immediate vicinity of the plant.

If you irrigate, make sure that the foliage either doesn't get wet (direct water to the roots only) or water early enough in the day so the foliage can dry by nightfall. You can't do much about rain or heavy dew wetting the leaves of course, but otherwise keeping the foliage dry discourages infection, since spores usually need damp leaf surfaces to more effectively infect the tissues. Make sure the plant is only being watered when it needs it -- when the soil around six inches deep begins to feel fairly dry to the touch at that depth.

As to the flowers being less prolific, that is probably due to environmental conditions. Several things can cause a Bigleaf Hydrangea not to bloom, such as impacts from pruning, deer, and weather. Flower buds on Bigleaf Hydrangeas form on the "old wood," which means they develop the season prior to opening on stems that are already a year old. (Growth produced the current year is called "new wood.") Therefore, this year's flowers actually developed last summer/autumn and spent the winter dormant on the stems, even if not noticeable at the time. Because the buds are ready-to-go on the plant all winter, they are vulnerable to damage or removal before they would be opening come summertime. Some hydrangea varieties are capable of reblooming, where they can grow replacement and additional flowers throughout the summer, but not all can do this, especially older varieties that have been on the market for decades. (Reblooming is a relatively new feature of modern varieties, though the number of varieties capable of this increases often these days because of plant breeding work.)

Deer can eat hydrangea buds as they browse, particularly in winter when they explore other food sources as they get hungry. Pruning at the wrong time will also remove buds; the best time to prune (though pruning isn't required to maintain plant health) is just after the first batch of flowers is spent around early to midsummer. Autumn, winter, or early spring pruning will remove flower buds. When our spring weather fluctuates and warm spells encourage plants to break dormancy, this can also make overwintering flower buds vulnerable to the frosts that inevitably return before the weather moderates later in spring. We have seen many occasions when hydrangeas break dormancy early and a freeze kills the buds that have lost their cold tolerance. Some hydrangea varieties are less bud-hardy than others; for instance, those sold in smaller pots as Easter-season indoor décor, forced into bloom a bit early because they're grown in a greenhouse, are the types likely to experience this problem. Varieties sold as hardy outdoor shrubs should be reliable, though. Covering cold-sensitive or dormancy-broken hydrangeas on a spring night with frost forecast using frost blanket material (similar to a vegetable garden's floating row cover, just a bit thicker) might help give it the few degrees of protection needed to avoid bud damage.

Lastly, if the shrub is getting more shade that it used to, such as being near a larger shrub or tree that has matured and is blocking more light, then this reduction in light level could be responsible for reduced bloom. Hydrangeas grow perfectly well in part shade, but fuller/deeper shade can cause sparser flowering. If that's the case, the simplest solution is to move the plant to a more partly-sunny location, if possible.

Miri