Brown spots on my plant's leaves — what kind am I looking at?

Take the plant to a window. Look at a spot closely and then look at the pattern across the whole plant — the pattern matters as much as the spot.

• Fungal or bacterial spot. Round or irregular, brown or black, often with a yellow ring around it, sometimes with a darker margin. It gets bigger over days and appears on new leaves it was not on last week. Spreading is the diagnostic — nothing else here spreads. It follows damp leaves, still air and crowding.
• Sun scorch. A dry, pale-brown or bleached patch, papery, usually on the side of the plant facing the window and on the leaves that get the most light. It does not spread and it does not have a halo. It arrives after a move, a change of season, or a sunny spell through glass, which magnifies the heat.
• Overwatering damage. Soft, dark, sometimes almost translucent patches, often starting at the base of the leaf or on the oldest leaves first, frequently with general yellowing. Check the compost: if it is wet, this is the answer and the guide you want next is overwatering.
• Pests. Many small spots rather than a few large ones, with a dusty or stippled look between them, and something on the undersides. Turn a leaf over with a torch before deciding anything.

A brown spot is dead tissue. The plant cannot repair it, so a spot that has stopped growing is history rather than an active problem — the question is only whether the cause has gone.

Fungal and bacterial spots are living organisms in the leaf, which is why they spread and why moving air and dry leaves matter more than any spray. Scorch is a burn: the cells in that patch were cooked, and the rest of the leaf is unaffected, which is why the edge of a scorch mark is so sharp. Waterlogging damage is the leaf being starved by roots that cannot function — the spots are a symptom of something happening below the compost, not on the leaf at all.

This is where too much light finally gets named. Owners are told constantly that houseplants need bright light, and much less often that direct sun through glass in a south-facing window will burn a shade plant in an afternoon. A calathea or a peace lily moved to a bright sill in June is the classic case: pale dry patches on the leaves facing out, within days.

Isolate it if the spots are spreading.

Move it away from other plants until you know. Nothing here is contagious except the fungal and bacterial kind, and that kind is genuinely contagious.

Remove the worst leaves

— a few, not half the plant. A leaf that is more brown than green is doing the plant no good; a leaf with one spot is still working and should stay.

Stop wetting the leaves.

Water the compost, not the plant. Do not mist anything with spreading spots.

Get air moving.

Space the plants out, open the door, let the leaves dry after watering. Still, humid, crowded air is what fungal spots need.

Move it out of direct sun

if the patches are dry and on the window side. A metre back from the glass, or a sheer curtain, is usually enough.

Check the compost.

If it is wet and the spots are soft, the pot is the problem and none of the above matters until that is fixed.

Only then consider a treatment.

Categories, not brands: a fungicide approved for houseplant use, applied at the interval on the label. If the cause was scorch or water, a treatment does nothing at all.

• Do not cut off every marked leaf. Stripping a plant that is already struggling removes the capacity it needs to recover.
• Do not mist a plant with spreading spots. It is the single most reliable way to make a fungal problem worse.
• Do not move a scorched plant into a dark corner. Overcorrecting trades one problem for another; a metre back from the same window is usually right.
• Do not feed it. A damaged plant cannot use it, and in the resting season feeding is paused anyway — which is what the app will tell you.
• Do not assume it is a disease because it is brown. Three of the four causes here are not infections, and the treatment for an infection does nothing for the other three.

Big thin leaves show spots most — monstera and fiddle-leaf fig, where brown patches are the classic panic and are usually about water or a cold draught rather than disease — while dracaena and the shade-loving calathea scorch readily if they are moved somewhere brighter than they are used to.

• African VioletSaintpaulia ionantha
• Cast Iron PlantAspidistra elatior
• CliviaClivia miniata
• Easter LilyLilium longiflorum
• Fiddle Leaf FigFicus lyrata
• Maidenhair FernAdiantum raddianum
• Prickly PearOpuntia species
• BoxwoodBuxus
• Butterfly IrisIris spuria
• CarnationDianthus caryophyllus
• CatnipNepeta cataria
• China AsterCallistephus chinensis
• Christmas RoseHelleborus niger
• Coral BellsHeuchera sanguinea
• Holly FernCyrtomium falcatum
• HostaHosta plantaginea
• IrisIris germanica
• Iron Cross BegoniaBegonia masoniana
• Japanese MapleAcer palmatum
• Lace Flower VineEpiscia dianthiflora
• Lemon BalmMelissa officinalis
• MintMentha spicata
• Monterey CypressCupressus macrocarpa
• Mother FernAsplenium bulbiferum
• ParsleyPetroselinum crispum
• PierisPieris japonica
• Purple Passion VineGynura aurantiaca
• RoseRosa
• SnapdragonAntirrhinum majus
• SpikemossSelaginella kraussiana
• Tiger LilyLilium lancifolium
• Trailing Watermelon BegoniaPellionia daveauana
• White StonecropSedum album

All 265 plants in the library →

What causes brown spots on houseplant leaves?

Four things, and they look different. Spreading spots with a yellow halo are fungal or bacterial; dry pale patches on the side facing the window are sun scorch; soft dark patches on the oldest leaves with wet compost are overwatering; many tiny spots with a stippled look are pests. Whether the spots spread is the quickest way to separate the first from the rest.

What is the difference between brown spots and brown tips?

Brown tips and edges are usually about water — how much, how often, or what is in it — and are covered on brown leaf tips. Brown spots sit inside the leaf and have a different set of causes entirely. Treating a spot as though it were a tip is why so much advice does not work.

Are brown spots on leaves contagious to my other plants?

Only the fungal and bacterial kind, and that kind is genuinely contagious — it spreads on splashed water and through still, crowded air. Scorch, overwatering damage and most pest marks will not move to a neighbouring plant on their own. If the spots are getting bigger and appearing on new leaves, isolate the plant.

Can too much sun cause brown spots?

Yes, and it is more common than people expect. Direct sun through glass magnifies the heat and will burn a shade plant within days of a move to a brighter spot. Scorch is dry, pale and papery, sits on the leaves facing the window, has a sharp edge, and does not spread.

Should I cut off leaves with brown spots?

Remove the badly affected ones — leaves that are more brown than green — and leave the rest. A leaf with one spot still feeds the plant. If the spots are spreading, take the worst leaves off, stop wetting the foliage, and move the plant away from its neighbours while you deal with it.

The RHS covers leaf spot diseases in detail for garden plants; this page is the indoor case, where three of the four common causes are not diseases at all. Sabz's Check-up asks where the damage sits and what the room has been like, and reads it against what you have logged — because a plant that moved to a new window last month and one that has been watered twice a week all summer are telling two different stories with the same brown patch.