Hello Milton,

These hydrangea seem to be suffering from environmental stress issues; likely water-related and possibly from too much sun as well. Are they shaded at all during the heat of the day? In our area, this species of hydrangea is not well-adapted to full sun (despite what some plant label tags claim) and some degree of shade is best. The curling leaf margins, browning, and discoloration suggest heat and moisture stress, even if they are not wilting.

Hydrangeas can get leaf-spotting fungal and bacterial infections, especially when the leaves are kept wet from irrigation, but we do not see any here - and not where we'd recommend any spray treatments. They do look nutrient-starved; if their roots are healthy, you can fertilize with a formulation made for acid-loving plants (ideally, though any well-balanced fertilizer should work). Unhealthy roots, such as those dying back from insufficient water or excessive water, will also cause nutrient deficiencies in the foliage. In that case, however, fertilizing will not solve the problem and the plant will simply need time to recover if the damaging cause (too wet, too dry) can be fixed.

When fertilizing works, the results may not be seen on older foliage because some discoloration from malnourishment is permanent and does not reverse itself; however, the new growth should show improvements with an even green color and no diffuse yellowing or red blushing. Red blushing of foliage on a few hydrangea varieties is perfectly normal, but it occurs most often when the plant is under stress and is rarely seen in partly-shaded, healthy growth. Such a color change in autumn would be more typical on those varieties.

Miri

Shaded afternoon exposures are a good choice, so that's good. The irrigation system may be the issue, then - if being run daily, this is probably both too often and too little water, if it only runs for (guessing a common occurrence) 15 minutes or so per zone. The only plants that should receive such frequent, light waterings is newly-planted grass seed or sod. Otherwise, established landscape plants require more thorough soakings spaced further apart. Light waterings only serve to soak the top inch or so of soil (at best, since mulch will absorb some, and a lot evaporates) and do not wet deeper roots; frequent wetness also allows more disease spores to survive and infect plants. If the irrigation system is needed to water in this way (if you have new grass), then make sure the hydrangeas and other garden plants are being checked and soaked independently with a hose or watering can. Otherwise, alter the entire sprinkler program to run differently - about an hour per zone in the morning and only one day a week. You may need to wean things off of the prior schedule by running it twice a week for a couple of rounds first. This hour-once-a-week suggestion is a guideline - you'll have to experiment and see how often the soil is drying out 6" down and how long the sprinklers need to run to deliver the equivalent of 1" of rain. Setting out a shallow can in the sprinkled area will let you know how long this takes.

Fertilizer brand doesn't really matter; several companies manufacture blends made for acid-lovers, which hydrangea are (as are many other common garden plants like azalea, rhododendron, camellia, holly, etc.). Granular/pelleted dry-applied organic formulations will last the longest and release nutrients the slowest (a benefit to avoid runoff waste and shocking roots); watered-in liquid types deliver nutrients more quickly but over a shorter time period. They each have their pros and cons in this way, but either is fine. You may find that sufficient watering alone will be nourishing enough, since drought-stressed roots will have trouble absorbing what they need even if it's already in the soil in sufficient quantities.

Correct, this does not look like any of the symptoms of typical fungal diseases that hydrangeas contract; those symptoms are pretty distinctive. Frequent wetting of the foliage, though, does create conditions for them to prosper - another reason to change the irrigation pattern to a less-frequent schedule.

Miri