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Rosemary spots on leaves: causes and what to do

8 results in the diagnosis tree begin with spots on the leaves, 5 of them marked likely when the answers fit. They are ordered here for Rosemary (Salvia rosmarinus), using what its sources say about light, soil moisture, humidity and pests and diseases and one problem recorded for it.

Sources last read 14 September 2026.

Start the diagnosis for this Rosemary

Rosemary (Salvia rosmarinus), the whole plant.
Syrio, CC BY-SA 4.0 · Wikimedia Commons

Salvia rosmarinus, synonym Rosmarinus officinalis, commonly known as rosemary, is a shrub with fragrant, evergreen, needle-like leaves and purple or sometimes white, pink, or blue flowers. It is a member of the mint family, Lamiaceae. Wikipedia, CC BY-SA 4.0

Native range: Medit. (temperate). Also sold as Anthos, old man, rose of the sea and southernwood.

What Rosemary’s sources say that bears on this

Light
Full sun
RHS · read 13 September 2026
Soil moisture
Well-drained
RHS · read 13 September 2026
Humidity
ASHRAE recommends indoor relative humidity between 30% and 60%
Penn State Extension · read 13 September 2026
Pests and diseases
Can be troubled by aphids. Diseases: southern blight.
NC State Extension · read 13 September 2026
Can be troubled by scale insects, tortrix moth, sage leafhopper, cuckoo spit and rosemary beetle. Diseases: foot and root rots, Verticillium wilt, powdery mildews and, rarely, honey fungus.
RHS · read 13 September 2026

How this shows up on a Rosemary

Dry scorched spots after a move into a sunnier spot

On a rosemary the scorch appears within a few days of a sunny spell or a move, and it does not spread afterward.

Nothing here disputes the full sun its source names. The damage comes from the change: foliage formed in lower light is thin, and a sudden move into direct sun bleaches it faster than tougher growth can replace it.

Telling it apart: Whether the patches grow. Scorch is done once it happens; a leaf spot keeps spreading.

RHS · read 13 September 2026

Possible causes, likeliest first for a Rosemary

  1. Most likely spider mites

    • Can cause skin allergy. Use gloves and protective gear when handling it. RHS · read 13 September 2026

    Why: Spider mites feed on individual leaf cells, and each emptied cell shows as a pale speck.

    What to try:

    • Move the rosemary away from other plants.
    • Wash the leaves, top and underside, with a strong spray of water in a shower or sink.

    What would settle it: Hold a sheet of white paper under a leaf and tap the leaf. Tiny specks that move across the paper are mites.

    Check this with the questions

  2. Most likely powdery mildew

    • Can cause skin allergy. Use gloves and protective gear when handling it. RHS · read 13 September 2026

    Why: A white coating that wipes off is the surface growth of a fungus.

    What to try:

    • Remove the worst-affected leaves.
    • Improve air movement around the rosemary and space it away from others.

    What would settle it: Wipe a patch. Powdery mildew comes away and leaves a yellowed patch beneath. White that does not wipe off is part of the leaf, or a mineral deposit from hard water.

    Check this with the questions

  3. Most likely thrips

    • Can cause skin allergy. Use gloves and protective gear when handling it. RHS · read 13 September 2026

    Why: Thrips rasp the leaf surface and drink what leaks out, which leaves silvery, papery streaks.

    What to try:

    • Move the rosemary away from other plants.
    • Wash the leaves thoroughly and remove badly damaged ones.

    What would settle it: Tap a leaf over white paper. Thrips are slender, fast-moving and about the size of a comma; they are easy to see once they are on paper.

    Check this with the questions

Less likely for a Rosemary, still possible

Questions

What usually causes spots on the leaves on a Rosemary?
For Rosemary: most likely spider mites, most likely powdery mildew and most likely thrips.
How can I tell which one it is on my Rosemary?
What do the marks look like? Pale, dry, bleached patches on the side facing the window; Brown or black spots, many with a yellow ring around them; Tiny pale speckles all over, sometimes with fine webbing underneath; A white powdery coating that wipes off; Silvery streaks with tiny black dots; Dark, soft, water-soaked patches.
What do Rosemary's sources say about its light?
RHS: Full sun.
What does this look like on a Rosemary?
On a rosemary the scorch appears within a few days of a sunny spell or a move, and it does not spread afterward. Telling it apart: Whether the patches grow. Scorch is done once it happens; a leaf spot keeps spreading.
Is Rosemary safe to handle while I check it?
Its sources list it as toxic to people. Wash your hands after handling the roots or sap, and keep trimmings away from pets.

Something else wrong with the Rosemary?

Everything the sources say about Rosemary

What this does not cover

This page orders a decision tree's results using a plant's sourced care. It has not seen your plant, its pot or its window, and two problems at once are common: that is the usual reason a confident answer turns out wrong. The questions in the diagnosis tool narrow it further than a list can.