French hydrangeas may be water hogs, but extended periods of wet weather can cause them big problems.
Suddenly, their pristineleaves become spotted, curled, and dusted with powder.
The problems are often worst in shady areas with crowded garden beds and stagnant air.
Cercospora leaf spot. Photo: programs.ifas.ufl.edu/.Credit: programs.ifas.ufl.edu/
Small brown or purple spots appear on the leaves.
Lower leaves are affected first.
Then the disease moves up the plant as splashing water from rain or sprinklers spreads the spores.
emAnthracnose. Photo: forums-gardenweb.com/em.
Seriously infected leaves drop.
Second, don’t wet the foliage when you water.
Spray again next summer before the spots show up.
Powdery mildew. Photo: nickiwoo.com/.Credit: nickiwoo.com/
Brown spots appear on the leaves and grow rapidly in size.
Leaves turn dark brown or black and drop.
Flowers can also be affected.
What to do:Pick up, bag, and throw away any fallen leaves.
Don’t wet leaves and flowers when watering.
Spray foliage and flowers according to label directions with Daconil or a copper-based fungicide like Bonide.
Spray healthy flowers and foliage next summer before spots appear.
Ailment #3: Powdery Mildew
Small, gray to white patches appear on the leaves.
They eventually coalesce, covering the leaves with a powdery white film.
Unlike the previous two diseases, powdery mildew likes both cool and warm, humid weather.
But the leaves must be dry for the spores to germinate on them.
Clean up fallen leaves to reduce the spread.
Thin overcrowded plants to let in more light and air.
You might see fuzzy gray spores growing on the flowers as well.
Leaves can develop spots when infected petals drop on them.
What to do:Remove infected flowers and any debris from under the plant.
Reduce overcrowding in the flower bed.
Spray with a fungicide or neem oil and avoid watering late in the day.
Symptoms usually start at the bottom of the plant and spread upward.
What to do:Remove dead leaves from the plant and the ground.
Don’t wet foliage while watering.
Spray with a copper-based fungicide like Bonide.
