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Research · November 2026

What goes wrong with plants: 12,905 problem guides, counted

Pocket Botanist has a short guide for each plant and each symptom it can show. We counted which causes come up across 12,905 of those guides, for 1,566 plants, from 226 houseplants to garden shrubs and trees. Here's what they name most often, and what changes indoors.

November 2026 edition, counted on October 31, 2026 from the plant data of October 26, 2026.

The short answer

  • Too much water leads for yellow leaves. Overwatering is named in 72% of the guides to yellow leaves, and in 88% of those for houseplants.
  • Leggy growth is a light problem. Too little light is named in 99.9% of the guides to leggy growth, and in 96% of those to plants that won't flower.
  • Brown tips point to dry air. Low humidity is named in 64% of the guides to brown leaf tips, and in 91% of those for houseplants.
  • Water comes up again and again. 48% of the 12,905 guides name a water cause: too much, too little, uneven watering or soil that won't drain. For drooping it's 93%, and for root rot 99%.
  • Indoors, the pests change. Aphids are named in 59% of all the pest guides, but for houseplants spider mites come first, in 48% of their pest guides, then mealybugs, in 40%.

Cause by cause

The five causes named most often for each symptom, as a share of that symptom's guides. Every bar uses the same scale, from 0 to 100%.

  • All 1,566 plants
  • The 226 houseplants

Yellow leaves

1,549 guides, 226 of them for houseplants.

Yellow leaves: the causes our guides name most oftenOverwatering, 72% of all guides and 88% for houseplants; Nutrient deficiency, 57% of all guides and 20% for houseplants; Too little light, 13% of all guides and 31% for houseplants; Underwatering, 9% of all guides and 16% for houseplants; Too much sun, 6% of all guides and 11% for houseplantsOverwatering72%88%Nutrient deficiency57%20%Too little light13%31%Underwatering9%16%Too much sun6%11%
Show the numbers
Yellow leaves: guides naming each cause
CauseAll plantsHouseplants
Overwatering72% (1,116 of 1,549)88% (198 of 226)
Nutrient deficiency57% (886 of 1,549)20% (46 of 226)
Too little light13% (206 of 1,549)31% (70 of 226)
Underwatering9% (132 of 1,549)16% (37 of 226)
Too much sun6% (95 of 1,549)11% (25 of 226)

Yellow leaves on plants: causes and fixes

Brown tips

1,402 guides, 220 of them for houseplants.

Brown tips: the causes our guides name most oftenLow humidity, 64% of all guides and 91% for houseplants; Underwatering, 44% of all guides and 26% for houseplants; Salt buildup, 41% of all guides and 40% for houseplants; Uneven watering, 29% of all guides and 23% for houseplants; Heat stress, 7% of all guides and 1% for houseplantsLow humidity64%91%Underwatering44%26%Salt buildup41%40%Uneven watering29%23%Heat stress7%1%
Show the numbers
Brown tips: guides naming each cause
CauseAll plantsHouseplants
Low humidity64% (891 of 1,402)91% (200 of 220)
Underwatering44% (617 of 1,402)26% (57 of 220)
Salt buildup41% (568 of 1,402)40% (87 of 220)
Uneven watering29% (406 of 1,402)23% (51 of 220)
Heat stress7% (96 of 1,402)1% (3 of 220)

Brown leaf tips on plants: causes and fixes

Drooping

1,450 guides, 214 of them for houseplants.

Drooping: the causes our guides name most oftenUnderwatering, 91% of all guides and 90% for houseplants; Heat stress, 38% of all guides and 11% for houseplants; Root rot, 28% of all guides and 56% for houseplants; Root damage, 15% of all guides and 3% for houseplants; Too little light, 5% of all guides and 7% for houseplantsUnderwatering91%90%Heat stress38%11%Root rot28%56%Root damage15%3%Too little light5%7%
Show the numbers
Drooping: guides naming each cause
CauseAll plantsHouseplants
Underwatering91% (1,317 of 1,450)90% (192 of 214)
Heat stress38% (556 of 1,450)11% (23 of 214)
Root rot28% (412 of 1,450)56% (119 of 214)
Root damage15% (216 of 1,450)3% (7 of 214)
Too little light5% (66 of 1,450)7% (14 of 214)

Drooping plants: causes and fixes

Leaf drop

992 guides, 190 of them for houseplants.

Leaf drop: the causes our guides name most oftenUnderwatering, 39% of all guides and 17% for houseplants; Temperature shock, 27% of all guides and 53% for houseplants; Sudden change in conditions, 17% of all guides and 20% for houseplants; Overwatering, 16% of all guides and 31% for houseplants; Too little light, 13% of all guides and 13% for houseplantsUnderwatering39%17%Temperature shock27%53%Sudden change in conditions17%20%Overwatering16%31%Too little light13%13%

For houseplants, the cause named most often is temperature shock: 53% of their guides.

Show the numbers
Leaf drop: guides naming each cause
CauseAll plantsHouseplants
Underwatering39% (385 of 992)17% (32 of 190)
Temperature shock27% (266 of 992)53% (100 of 190)
Sudden change in conditions17% (173 of 992)20% (38 of 190)
Overwatering16% (163 of 992)31% (58 of 190)
Too little light13% (124 of 992)13% (24 of 190)

Plants dropping leaves: causes and fixes

Spots

1,337 guides, 188 of them for houseplants.

Spots: the causes our guides name most oftenLeaf spot, 63% of all guides and 69% for houseplants; Powdery mildew, 26% of all guides and 7% for houseplants; Rust, 10% of all guides and 1% for houseplants; Water on the leaves, 9% of all guides and 5% for houseplants; Too much sun, 8% of all guides and 11% for houseplantsLeaf spot63%69%Powdery mildew26%7%Rust10%1%Water on the leaves9%5%Too much sun8%11%
Show the numbers
Spots: guides naming each cause
CauseAll plantsHouseplants
Leaf spot63% (838 of 1,337)69% (129 of 188)
Powdery mildew26% (341 of 1,337)7% (13 of 188)
Rust10% (140 of 1,337)1% (1 of 188)
Water on the leaves9% (125 of 1,337)5% (10 of 188)
Too much sun8% (109 of 1,337)11% (21 of 188)

Spots on plant leaves: causes and fixes

Not flowering

983 guides, 103 of them for houseplants.

Not flowering: the causes our guides name most oftenToo little light, 96% of all guides and 92% for houseplants; Too much nitrogen, 22% of all guides and 4% for houseplants; Plant too young, 18% of all guides and 27% for houseplants; Pruning mistakes, 13% of all guides and 0% for houseplants; No cool rest period, 10% of all guides and 19% for houseplantsToo little light96%92%Too much nitrogen22%4%Plant too young18%27%Pruning mistakes13%0%No cool rest period10%19%
Show the numbers
Not flowering: guides naming each cause
CauseAll plantsHouseplants
Too little light96% (940 of 983)92% (95 of 103)
Too much nitrogen22% (219 of 983)4% (4 of 103)
Plant too young18% (178 of 983)27% (28 of 103)
Pruning mistakes13% (127 of 983)0% (0 of 103)
No cool rest period10% (102 of 983)19% (20 of 103)

Plants not flowering: causes and fixes

Pests

1,402 guides, 218 of them for houseplants.

Pests: the causes our guides name most oftenAphids, 59% of all guides and 17% for houseplants; Spider mites, 34% of all guides and 48% for houseplants; Scale insects, 20% of all guides and 33% for houseplants; Mealybugs, 14% of all guides and 40% for houseplants; Slugs and snails, 7% of all guides and 0.4% for houseplantsAphids59%17%Spider mites34%48%Scale insects20%33%Mealybugs14%40%Slugs and snails7%0.4%

For houseplants, the cause named most often is spider mites: 48% of their guides.

Show the numbers
Pests: guides naming each cause
CauseAll plantsHouseplants
Aphids59% (829 of 1,402)17% (38 of 218)
Spider mites34% (480 of 1,402)48% (104 of 218)
Scale insects20% (283 of 1,402)33% (72 of 218)
Mealybugs14% (193 of 1,402)40% (87 of 218)
Slugs and snails7% (100 of 1,402)0.4% (1 of 218)

Pests on plants: how to spot them and what to do

Root rot

1,422 guides, 224 of them for houseplants.

Root rot: the causes our guides name most oftenPoor drainage, 95% of all guides and 95% for houseplants; Overwatering, 92% of all guides and 92% for houseplants; Waterlogged soil, 5% of all guides and 5% for houseplants; Root rot, 1% of all guides and 0% for houseplants; Heavy clay soil, 0.4% of all guides and 0% for houseplantsPoor drainage95%95%Overwatering92%92%Waterlogged soil5%5%Root rot1%0%Heavy clay soil0.4%0%
Show the numbers
Root rot: guides naming each cause
CauseAll plantsHouseplants
Poor drainage95% (1,346 of 1,422)95% (213 of 224)
Overwatering92% (1,305 of 1,422)92% (205 of 224)
Waterlogged soil5% (73 of 1,422)5% (12 of 224)
Root rot1% (18 of 1,422)0% (0 of 224)
Heavy clay soil0.4% (6 of 1,422)0% (0 of 224)

Root rot in plants: causes and fixes

Leggy growth

1,418 guides, 222 of them for houseplants.

Leggy growth: the causes our guides name most oftenToo little light, 99.9% of all guides and 100% for houseplants; Lack of pruning, 35% of all guides and 51% for houseplants; Overcrowding, 17% of all guides and 1% for houseplants; Too much nitrogen, 16% of all guides and 2% for houseplants; Heat stress, 9% of all guides and 4% for houseplantsToo little light99.9%100%Lack of pruning35%51%Overcrowding17%1%Too much nitrogen16%2%Heat stress9%4%
Show the numbers
Leggy growth: guides naming each cause
CauseAll plantsHouseplants
Too little light99.9% (1,417 of 1,418)100% (222 of 222)
Lack of pruning35% (501 of 1,418)51% (114 of 222)
Overcrowding17% (243 of 1,418)1% (2 of 222)
Too much nitrogen16% (223 of 1,418)2% (5 of 222)
Heat stress9% (125 of 1,418)4% (8 of 222)

Leggy plants: causes and fixes

Curling leaves

950 guides, 157 of them for houseplants.

Curling leaves: the causes our guides name most oftenHeat stress, 62% of all guides and 24% for houseplants; Aphids, 46% of all guides and 8% for houseplants; Underwatering, 30% of all guides and 48% for houseplants; Low humidity, 15% of all guides and 60% for houseplants; Temperature shock, 5% of all guides and 17% for houseplantsHeat stress62%24%Aphids46%8%Underwatering30%48%Low humidity15%60%Temperature shock5%17%

For houseplants, the cause named most often is low humidity: 60% of their guides.

Show the numbers
Curling leaves: guides naming each cause
CauseAll plantsHouseplants
Heat stress62% (593 of 950)24% (37 of 157)
Aphids46% (441 of 950)8% (13 of 157)
Underwatering30% (287 of 950)48% (76 of 157)
Low humidity15% (147 of 950)60% (94 of 157)
Temperature shock5% (49 of 950)17% (26 of 157)

Curling leaves on plants: causes and fixes

The water problem

Five of the causes are about water: overwatering, underwatering, uneven watering, poor drainage and waterlogged soil. Count a guide once if it names any of them, and water comes up in 48% of all 12,905 guides, and in 50% of the guides for houseplants.

It's 85% for yellow leaves, 93% for drooping and 99% for root rot. Too much water and too little both show up, sometimes for the same symptom, so the soil is the thing to check, not the calendar.

The RHS advice is to check how moist the potting mix is before you water, rather than watering on a fixed schedule. Read the RHS advice.

Guides that name a water cause, by symptom

  • All 1,566 plants
  • The 226 houseplants
Guides that name a water cause, by symptomRoot rot, 99% of all guides and 99% for houseplants; Drooping, 93% of all guides and 93% for houseplants; Yellow leaves, 85% of all guides and 89% for houseplants; Brown tips, 73% of all guides and 50% for houseplants; Leaf drop, 67% of all guides and 64% for houseplants; Curling leaves, 34% of all guides and 54% for houseplants; Spots, 5% of all guides and 14% for houseplants; Leggy growth, 3% of all guides and 5% for houseplants; Not flowering, 2% of all guides and 0% for houseplants; Pests, 0.1% of all guides and 0% for houseplantsRoot rot99%99%Drooping93%93%Yellow leaves85%89%Brown tips73%50%Leaf drop67%64%Curling leaves34%54%Spots5%14%Leggy growth3%5%Not flowering2%0%Pests0.1%0%
Show the numbers
Guides that name a water cause, by symptom
CauseAll plantsHouseplants
Root rot99% (1,412 of 1,422)99% (221 of 224)
Drooping93% (1,347 of 1,450)93% (199 of 214)
Yellow leaves85% (1,316 of 1,549)89% (202 of 226)
Brown tips73% (1,030 of 1,402)50% (110 of 220)
Leaf drop67% (666 of 992)64% (121 of 190)
Curling leaves34% (322 of 950)54% (85 of 157)
Spots5% (71 of 1,337)14% (26 of 188)
Leggy growth3% (39 of 1,418)5% (11 of 222)
Not flowering2% (21 of 983)0% (0 of 103)
Pests0.1% (2 of 1,402)0% (0 of 218)

Winter indoors: dry air and sudden cold

With the heating on, indoor air dries out, and the RHS names dry air as a common winter problem for houseplants. The guides point the same way. Low humidity is named in 91% of the brown-tip guides for houseplants, against 64% across all plants. For curling leaves on houseplants it's the cause named most often, in 60% of their guides.

Sudden cold is the other winter trouble. For leaf drop on houseplants, the cause named most often is temperature shock, which we count together with cold drafts: 53% of their guides, against 27% across all plants.

Warm, dry rooms suit spider mites too. They're named in 48% of the pest guides for houseplants.

What helps this winter

  • Raise the humidity around the plant. Stand the pot on a tray of damp gravel or clay pebbles, with the water kept below the top of the stones, or group plants together.
  • Keep plants away from radiators, heaters and drafty doors, and don't leave them between a cold window and a closed curtain on a frosty night.
  • Water less. Growth slows in winter, so check how moist the soil is before you water instead of watering on a schedule.
  • Move plants closer to a bright window for the darker months.

This advice follows the RHS and Iowa State University Extension.

Every symptom, in detail

Each symptom has its own page: what to check first, the common causes and their fixes, and a link to every plant's guide.

How we counted

Each guide covers one plant and one symptom, such as why a monstera's leaves turn yellow. Google's Gemini model writes it for that species from the plant's care profile, under one set of instructions (prompt pb-plant-problems-v1-0-0), and these were written between September 19, 2026 and October 26, 2026. They are AI-written guidance, not records of real plants, so this page counts how often a cause is named across the guides. It doesn't measure how often plants get it. How the guides are made.

We counted the 12,905 English guides for the 1,566 plants with a page on this site, from the plant data of October 26, 2026. Fungi are left out. A guide counts once for a cause, however many of that cause's names it uses.

Most guides name two causes, so a symptom's shares add up to about 200%, and a cause that would have come third doesn't show at all. Each guide also rates its causes as likely, possible or rare. The charts count every mention; the CSV also says how many guides rated a cause likely.

Houseplants are the 226 plants whose care profile lists an indoor use or indirect light, the same test as our low-light houseplants list. It's a rough test, and the houseplant figures rest on fewer guides: 103 to 226 per symptom.

Names that mean the same thing count together: Insufficient sunlight and Low light count as too little light, and Dry air as low humidity. A few narrower causes count under a broader one: a named nutrient's deficiency as nutrient deficiency, cold drafts as temperature shock, fertilizer burn as salt buildup and named kinds of aphid as aphids. The table lists every name counted under each cause in the charts.

Show every name we counted

The names are as the English guides write them.

Names counted under each cause, with the number of guides that use each one
CauseNames countedNarrower causes counted under it
OverwateringOverwatering (2,524), Excessive watering (43), Excessive irrigation (4), Overwatering during dormancy (4), Severe overwatering (4), Summer overwatering (2), Overwatering in soil (1), Overwatering in winter (1), Watering too often (1)None
Nutrient deficiencyNutrient deficiency (698)Nitrogen deficiency (101), Iron chlorosis (58), Iron deficiency (26), Magnesium deficiency (2), Iron or nitrogen deficiency (1), Magnesium or potassium deficiency (1)
Too little lightInsufficient light (2,007), Insufficient sunlight (286), Low light (208), Low light levels (64), Lack of sunlight (58), Lack of light (27), Lack of direct sun (23), Low light conditions (19), Lack of direct sunlight (13), Too much shade (11), Inadequate light (8), Low light intensity (7), Light deficiency (6), Low light exposure (5), Lack of full sun (4), Lack of direct light (3), Lack of sun (3), Not enough sun (3), Deep shade (1), Light deprivation (1)None
UnderwateringUnderwatering (1,720), Drought stress (330), Dehydration (234), Severe dehydration (178), Severe drought (136), Extreme drought (32), Severe underwatering (30), Drying out (25), Extreme dehydration (11), Severe drought stress (9), Thirst (9), Drought (3), Low soil moisture (3), Underwatered (3), Insufficient water (2), Insufficient watering (2), Water deficiency (2), Extreme drought stress (1), Extreme underwatering (1), Inadequate watering (1), Lack of water (1), Soil dehydration (1), Summer drought stress (1), Under-watering (1), Underwatered soil (1), Water deficit (1)None
Too much sunSunburn (84), Sunscald (35), Too much direct sun (21), Too much light (20), Excessive light (7), Sun scorch (7), Too much sun (7), Excessive sunlight (5), Direct sunlight (4), Too much direct sunlight (4), Excessive direct sun (3), Direct sun exposure (2), Excessive sun exposure (2), Excessive direct sunlight (1), Excessive sun (1), Too much direct light (1)None
Low humidityLow humidity (1,024), Low humidity or dry air (10), Dry air (4)None
Salt buildupMineral buildup (217), Salt buildup (88), Salt accumulation (78), Salt or mineral buildup (13), Salt damage (11), Fertilizer salt buildup (7), Hard water buildup (4), Mineral salt buildup (3), Tap water salts (2), Fertilizer buildup (1), Salt buildup from fertilizer (1)Fertilizer burn (143)
Uneven wateringInconsistent watering (388), Inconsistent moisture (14), Irregular watering (1), Uneven watering (1), Water irregularity (1), Watering inconsistency (1)None
Heat stressHeat stress (1,182), Excessive heat (79), High temperatures (59), Extreme heat stress (22), Excessive warmth (12), Heat scorch (6), Excessive heat stress (3), Extreme heat (3), Heat exhaustion (1), High heat stress (1), Severe heat stress (1), Temperature too high (1)None
Root rotRoot rot (401)Phytophthora root rot (22), Phytophthora (4), Phytophthora infection (4)
Root damageRoot damage (134), Root stress (61), Root disturbance (14), Root issues (7)None
Temperature shockTemperature shock (164), Temperature stress (102), Sudden temperature change (25), Temperature fluctuations (14), Sudden temperature shift (5), Cold shock (2), Extreme temperature fluctuations (2), Sudden temperature drop (1), Sudden temperature shifts (1), Temperature swings (1)Cold drafts (26), Cold stress (11), Drafty environment (1)
Sudden change in conditionsEnvironmental shock (86), Environmental stress (26), Sudden environmental change (18), Sudden environmental changes (1)Light shock (18), Sudden light change (18), Sudden light changes (4), Light changes (2)
Leaf spotFungal leaf spot (570), Leaf spot disease (167), Leaf spot fungus (61), Leaf spot fungi (40)None
Powdery mildewPowdery mildew (341)None
RustRust fungus (115), Fungal rust (20), Rust (5)None
Water on the leavesWater splashing (62), Overhead watering (42), Water splash (9), Water splashes (7), Water on leaves (3), Water on foliage (2)None
Too much nitrogenExcessive nitrogen (227), Excess nitrogen (104), Excessive nitrogen fertilizer (90), Too much nitrogen (11), Excess nitrogen fertilizer (9), Excessive nitrogen fertilization (1)None
Plant too youngPlant maturity (43), Lack of maturity (30), Young age (30), Young plant (18), Insufficient maturity (13), Tree maturity (12), Young plant age (10), First year growth (6), Plant is too young (6), Immature plant (5), Immaturity (5)None
Pruning mistakesImproper pruning (114), Incorrect pruning (13)None
No cool rest periodLack of dormancy (22), Lack of winter dormancy (19), Lack of temperature drop (10), Lack of seasonal cooling (9), Lack of seasonal change (8), Lack of seasonal rest (8), Lack of winter chill (8), Improper dormancy (5), Insufficient cold period (4), Insufficient winter chilling (2), Lack of seasonal temperature drop (2), Insufficient chill hours (1), Insufficient chilling (1), Lack of chill hours (1), Lack of cold dormancy (1), Lack of cold exposure (1)None
AphidsAphids (1,253)Oleander aphids (6), Banana aphids (3), Soybean aphids (2), Sumac gall aphids (2), Black bean aphids (1), Filbert aphids (1), Palm aphids (1), Water lily aphids (1)
Spider mitesSpider mites (532)None
Scale insectsScale insects (245), Scale (38)None
MealybugsMealybugs (193)None
Slugs and snailsSlugs and snails (46), Slugs (36), Snails (18), Slugs or snails (15)None
Poor drainagePoor drainage (1,145), Poor soil drainage (185), Poorly draining soil (14), Inadequate drainage (1), Poor drainage site (1)None
Waterlogged soilWaterlogged soil (61), Stagnant water (12)None
Heavy clay soilHeavy clay soil (6)None
Lack of pruningLack of pruning (501)None
OvercrowdingOvercrowding (133), Crowding (103), Crowded conditions (4), Crowded planting (3)None

The limits

  • The guides are written by AI and can get a detail wrong. They're general information, not horticultural advice.
  • Every plant counts once, so a rare tree weighs the same as a common houseplant. The numbers describe our guides, not the plants people grow most.
  • The Spanish, French and German guides are translations of the English ones, so the counts are the same in every language.
  • This is one snapshot. The guides change over time, so a later edition can differ, but this one stays as published.

Checked against expert advice

We checked the three causes named most often for each symptom against advice from the RHS and US university extension services. For eight of the ten symptoms, the sources name the same causes: yellow leaves, brown tips, drooping, leaf drop, spots, not flowering, pests, and root rot.

  • Leggy growth, partly. Low light is the typical cause for Iowa State, and the RHS links weak, spindly growth to low light. We found no general RHS or extension advice naming lack of pruning or overcrowding as main causes. Iowa State also names too much fertilizer, which our guides name too.
  • Curling leaves, partly. The RHS lists curled leaves among the damage aphids do, and leaves that roll from heat stress. We found no general US extension page on curling leaves to check against.
  • Brown tips, one difference. The RHS pages we read name dry air and watering but not salt buildup, which Iowa State and Clemson both name.
  • Pests, one note. The RHS houseplant advice names mealybugs, scale insects, thrips and red spider mite, which matches our houseplant figures better than the all-plant ones, led by aphids.

Sources

  1. Royal Horticultural Society (RHS), How to help a poorly houseplant
  2. Royal Horticultural Society (RHS), Leaf damage on houseplants
  3. Royal Horticultural Society (RHS), Non-flowering woody plants
  4. Royal Horticultural Society (RHS), Aphids
  5. Royal Horticultural Society (RHS), Glasshouse red spider mite
  6. Royal Horticultural Society (RHS), Powdery mildews
  7. Royal Horticultural Society (RHS), Rust diseases
  8. Royal Horticultural Society (RHS), Phytophthora root rot
  9. Iowa State University Extension and Outreach, Aaron Steil, Diagnosing Houseplant Problems from Improper Environmental Conditions
  10. Clemson Cooperative Extension, Home & Garden Information Center, Houseplant Diseases & Disorders (HGIC 2251)
  11. University of Wisconsin-Madison Division of Extension, Brian Hudelson and Laura Jull, Root Rots on Houseplants
  12. Colorado State University, Agricultural Biology, Houseplant pests

Use the data

Every number in the charts, plus each cause named in at least ten guides for a symptom, is in one CSV file, with English column names. Download the CSV (35 kB).

You're free to use the data and the charts under CC BY 4.0. Please credit Pocket Botanist and link to this page.

Suggested credit

Source: Pocket Botanist, a count of 12,905 AI-written plant problem guides, November 2026.

As HTML:

Source: <a href="https://www.pocketbotanist.app/research/plant-problems">Pocket Botanist</a>

https://www.pocketbotanist.app/research/plant-problems-2026-11.csv

Want a different cut, like one symptom for houseplants only? Ask us through the press page.

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