Brown Leaves on My Hydrangea

Root Nematodes

• Root nematodes cause problems in hydrangeas, according to the University of California Extension. The eel-like, microscopic insects infest and feed on plant roots. Brown foliage is a common above-ground symptom of root nematode infestation.

Rust

• Rust is a possible hydrangea disease, states the University of California Extension. The fungal disease leads to the development of spore masses on foliage undersides. The upper leaf area of infected foliage starts to turn yellow or brown.

Armillaria Root Rot

• Hydrangeas are also susceptible to armillaria root rot, states the University of California Extension. The fungal disease affects the roots and is caused by Armillaria mellea. Stunted and discolored foliage accompanied by leaf drop are early symptoms of the disease.