Asked July 29, 2020, 9:19 AM EDT

my years old (mop head?) hydrangeas have stopped blooming, even though, winter 2020 was mild.
some are in sun, others in shade.
in sun, the leaves have brown shrivel patches.
one, in shade, gets only a couple of blossoms
I don't remember pruning ugly old stems too early, but maybe I needed to wait :(
Thanks for your help in bringing back blossoms.

Montgomery County Maryland

1 Response

Some reasons for no bloom include improper pruning, possible deer browsing, excessive nitrogen fertilizer, poor environmental conditions, and low winter/spring temperatures. This can be an issue as we had a late cold snap this spring and this affected flower buds so no bloom.
However, there are some newer cultivars of bigleaf hydrangeas that bloom on old and new wood such as "Endless Summer" and you would get bloom later in the season.

We notice that the hydrangea in the left photo has some leaf scorch and leaf spots. The scorch and wilting is due to hot afternoon sun and not enough moisture for the roots. Hydrangeas are prone to multiple leaf spots, fungal and bacterial(middle photo). Some fungal diseases are becoming more common on hydrangeas and different cultivars vary in their susceptibility. The damage is cosmetic and will have to run its course.
Fungicides are not recommended as you would have to spray all season.
Avoid overhead watering. Remove any fallen leaves from around the base of the shrub at the end of the growing season. These sanitation practices will help to manage the disease from year to year.
See more on fungal leaf spots https://extension.umd.edu/hgic/topics/fungal-leaf-spots-shrubs

Right photo - looks like some pruning may have been done. Here is our page on pruning https://extension.umd.edu/hgic/topics/guide-pruning-hydrangeas

Hydrangeas grow best in morning sun and afternoon shade or dappled shade in a moist well drained soil. Hydrangeas will be stressed in full or afternoon sun and will require more moisture during dry periods. You will have to water deeply so the soil is moist like a wrung out sponge. Make sure mulch is no thicker than several inches and away from the base of the stems.

If possible, you may want to transplant the hydrangea located in the sun to a location that receives dappled shade or morning sun and afternoon shade in the fall or spring.