Roses problems
Black spot and powdery mildew account for the great majority of rose complaints, and both are largely preventable by watering at the base and giving the plant air.
Start from what you can see
Each of these has more than one possible cause, and each page separates them.
Everything that commonly affects roses
Most serious first. Most of the list is treatable or can be ignored.
Growing conditions
Only new growth is affected; older leaves are untouched.
Pest
Fine even stippling rather than discrete spots or holes.
Fungal disease
V-shaped yellow wedges at the leaf margins.
Pest
Dense clusters on new shoots and flower buds rather than scattered individuals.
Fungal disease
Fringed, feathery edges to each black spot — not a clean circle.
Fungal disease
Grey fuzzy growth that releases a visible puff of spores when touched.
Nutrient problem
Green veins on a yellow leaf — the net pattern is diagnostic.
Pest
Leaves reduced to a lace of veins rather than holed or notched.
Nutrient problem
Whole leaf yellows evenly, veins included.
Fungal disease
Orange powder that rubs off onto a finger or a white tissue.
Pest
Silvery or bronze streaks, not spots or holes.
Growing conditions
Leaves dry and crisp rather than soft and limp.
Fungal disease
White powder on the top of the leaf that rubs off with a finger.
Fungal disease
Wipes off with a damp cloth, unlike any true leaf disease.
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.
Diagnose your roses
Already filtered to roses. Add the symptoms and where the trouble started.
1.What plant is it?
Many problems are specific to one family, so this removes a large share of the list straight away.
2.What does it look like?
optionalPick everything you can see. Any one match keeps a cause on the list, because you rarely see the whole picture at once.
3.Which part is affected?
optionalIf the roots are involved you will have to unpot or dig to find out — and with a declining plant that is usually the most informative thing you can do.
4.Where did it start?
optionalThe most underused question in plant diagnosis. Trouble that begins at the bottom means something very different from trouble that begins at the top.
- Herbicide DamageAct nowGrowing conditions
- Spider MitesAct nowPest
- Verticillium WiltAct nowFungal disease
- AphidsTreatablePest
- Black SpotTreatableFungal disease
- Grey Mould (Botrytis)TreatableFungal disease
- Iron ChlorosisTreatableNutrient problem
- Japanese BeetlesTreatablePest
- Nitrogen DeficiencyTreatableNutrient problem
- RustTreatableFungal disease
- ThripsTreatablePest
- UnderwateringTreatableGrowing conditions
- Powdery MildewMostly cosmeticFungal disease
- Sooty MouldMostly cosmeticFungal disease