Roses black spots on leaves
There are 2 common causes, and they need completely different responses — so working out which one you have matters more than treating quickly.
None of them will normally kill the plant.
Check these two things first
- Push a finger into the soil, two knuckles deep. Wet soil plus a wilting plant means too much water, not too little — and it is the commonest reason a plant is dying. Dry soil plus crisp leaves means the opposite. The leaves look nearly identical either way, so the soil is what tells you.
- Turn a damaged leaf over. Half of all diagnoses live on the underside: fuzz means downy mildew, fine webbing means spider mites, clusters of insects mean aphids. Nothing on the top of a leaf is as informative.
Most garden problems are cosmetic and resolve without treatment. Reach for a spray last, not first.
The 2 causes, and how to tell them apart
1.Black Spot
TreatableFungal disease
Round black spots up to half an inch across with feathery, fringed edges rather than clean ones. The leaf around each spot turns bright yellow, and leaves drop from the bottom of the bush upward.
How to know it is this one
Fringed, feathery edges to each black spot — not a clean circle.
2.Sooty Mould
Mostly cosmeticFungal disease
A black, dry, soot-like film coating the upper surfaces of leaves and stems. It wipes off with a damp cloth, leaving green leaf underneath, and it is always accompanied by stickiness.
How to know it is this one
Wipes off with a damp cloth, unlike any true leaf disease.
Still not sure?
The diagnostic key adds two more questions — which part is affected and where the trouble started — and those usually settle it.
Run the diagnostic key