GrowingHQ
Leaves

Dark or black spots on leaves

Distinct dark spots on the leaf, as against a general browning or a spreading patch. What matters diagnostically is the edge and the company they keep: a sharp edge, a diffuse fringed edge, a yellow halo, a ring of pustules underneath, or angular blocks bounded by the veins each point somewhere different.

What causes it, and how to tell them apart

Work down the list making the observation under each heading. GrowingHQ will not guess which one you have — the observation is the answer.

  1. Rose black spotvery common
    source

    Sourced guidancehigh confidence

    • Royal Horticultural Society: Rose black spot

    Checked 2026-08-13

    How to tell

    Only on roses. The spots have a diffuse fringed margin rather than a sharp one, and yellowing spreads outwards from them before the leaf falls.

    source

    Horticultural consensusmoderate confidence

    No external citation — see the evidence type above.

    Checked 2026-08-13

    If it is this, do first

    Pick off and bin affected leaves, and clear fallen ones from beneath the plant — the fungus overwinters there and reinfects in spring.

    source

    Sourced guidancehigh confidence

    • Royal Horticultural Society: Rose black spot — control

    Checked 2026-08-13

  2. Downy mildewcommon
    source

    Sourced guidancemoderate confidence

    • Royal Horticultural Society: Downy mildew

    Checked 2026-08-13

    How to tell

    The patches are angular, bounded by the leaf veins into blocks, with greyish or purplish fuzz on the UNDERSIDE directly beneath them.

    source

    Horticultural consensusmoderate confidence

    No external citation — see the evidence type above.

    Checked 2026-08-13

    If it is this, do first

    Improve airflow, stop overhead watering, and remove affected leaves.

    source

    Sourced guidancemoderate confidence

    • Royal Horticultural Society: Downy mildew — control

    Checked 2026-08-13

  3. Rustcommon
    source

    Sourced guidancemoderate confidence

    • Royal Horticultural Society: Rust diseases

    Checked 2026-08-13

    How to tell

    Raised pustules on the underside that shed orange or brown powder when rubbed with a finger. The upper surface shows only pale spots above them.

    source

    Horticultural consensusmoderate confidence

    No external citation — see the evidence type above.

    Checked 2026-08-13

    If it is this, do first

    Remove affected leaves and space or thin the planting to dry the foliage faster.

    source

    Sourced guidancemoderate confidence

    • Royal Horticultural Society: Rust diseases — control

    Checked 2026-08-13

Where GrowingHQ holds more for one plant

This page lists the causes across every plant. The plants below are the ones where something about that plant changes the answer — different candidates, or a different observation that separates them.

Herbs

Ornamentals

Commonly reported on