Symptom checker · 142 symptoms · free, no account
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Guidance, not a guarantee. The checker weighs common causes against what you tell it; confirm with the tests before you treat, change one thing at a time and watch the new growth.
Every symptom, and what usually causes it
Each sign has its own page with the likely causes ranked, how to tell them apart and the fix for each.
Older, lower leaves
- Lower (older) leaves turning evenly yellowLikely causes: Nitrogen deficiency, Normal late-flower fade (senescence), Overwatering (roots short of air)
- Yellow between the veins on older leaves, veins stay greenLikely causes: Magnesium deficiency, Low root-zone pH starving calcium and magnesium, Unbuffered or new coco pulling calcium and magnesium
- Yellow edges and leaf teeth on older leavesLikely causes: Potassium deficiency, Manganese toxicity (usually low pH), Salt build-up in the root zone
- Fan leaves yellowing late in flower while buds keep ripeningLikely causes: Normal late-flower fade (senescence)
- Seedling leaves (cotyledons) yellowingLikely causes: Seed leaves yellowing as true leaves take over (normal), Overwatering (roots short of air), Nitrogen deficiency
- Dark olive or brown sunken spots on older leavesLikely causes: Phosphorus deficiency, High pH reducing phosphorus availability
- Round brown spots with yellow halos on lower leavesLikely causes: Septoria leaf spot
- Tan, crispy scorched edges on older leavesLikely causes: Potassium deficiency, Nutrient burn (feed too strong), Ammonium toxicity (too much NH4 in the feed)
- Brown, burnt leaf tipsLikely causes: Nutrient burn (feed too strong), Salt build-up in the root zone, Sodium build-up (softened water, coco, recirculation)
- Brown or dark speckling and bronzing on older leavesLikely causes: Manganese toxicity (usually low pH), Low root-zone pH starving calcium and magnesium, Iron and manganese excess at very low pH
- Lower leaves dying and dropping quicklyLikely causes: Nitrogen deficiency, Shaded lower leaves dying back (normal), Septoria leaf spot
- Dark green, glossy leaves with tips hooking down (the claw)Likely causes: Nutrient burn (feed too strong), Too much nitrogen, Overwatering (roots short of air)
- Leaf edges curling up (canoeing)Likely causes: Heat stress, Air too dry / VPD too high, Light burn: too much light for the plant's climate and CO2
- Leaf edges rolling under, leaves curling downward without darkeningLikely causes: Heat stress, Calcium deficiency (often a delivery problem), CO2 set far too high
- Red-purple petioles with yellowing lower leavesLikely causes: Nitrogen deficiency, Normal late-flower fade (senescence)
- Dark, dull blue-green leaves with purple or bronze blotchesLikely causes: Cold stress, High pH reducing phosphorus availability, Phosphorus deficiency
- Purple or red veins, mostly on leaf undersidesLikely causes: Genetic purple colour (anthocyanin), Cold stress, Phosphorus deficiency
- Yellow tips on lower fan leaves moving down the leafletLikely causes: Nitrogen deficiency, Potassium deficiency
New growth
- New growth evenly pale or yellowLikely causes: High root-zone pH locking out iron, manganese, zinc, boron and copper, Aphids, Sulfur deficiency
- Yellow between the veins on the newest leaves, veins greenLikely causes: High root-zone pH locking out iron, manganese, zinc, boron and copper, Hard, alkaline water pushing pH up over weeks, Uncalibrated or failing pH or EC meter
- Netted yellowing on upper and middle leaves with small tan specksLikely causes: High root-zone pH locking out iron, manganese, zinc, boron and copper, Manganese deficiency
- New leaves almost whiteLikely causes: Light bleaching at the canopy top, High root-zone pH locking out iron, manganese, zinc, boron and copper, Iron deficiency (usually high pH)
- Yellow then tan edges on new leavesLikely causes: High root-zone pH locking out iron, manganese, zinc, boron and copper, Calcium deficiency (often a delivery problem), Zinc deficiency
- Top leaves or bracts bleached white or yellow nearest the lightLikely causes: Light bleaching at the canopy top, Heat or light stress foxtailing on the top colas, Light burn: too much light for the plant's climate and CO2
- Rust-brown spots on newer and middle leavesLikely causes: Calcium deficiency (often a delivery problem), Low root-zone pH starving calcium and magnesium, Unbuffered or new coco pulling calcium and magnesium
- Small tan dead specks between veins on upper leavesLikely causes: Manganese deficiency
- Crispy, papery or scorched top leavesLikely causes: Heat stress, Light burn: too much light for the plant's climate and CO2, Air too dry / VPD too high
- Leaves folding up along the midrib (taco)Likely causes: Heat stress, Light burn: too much light for the plant's climate and CO2, Air too dry / VPD too high
- Twisted, distorted or crinkled new growthLikely causes: Calcium deficiency (often a delivery problem), Broad mites, Aphids
- Glossy, stiff, curled growing tips that stop growingLikely causes: Broad mites
- Growing tips dying or abortingLikely causes: Calcium deficiency (often a delivery problem), Boron deficiency, Broad mites
- Small, narrow or cupped new leavesLikely causes: Calcium deficiency (often a delivery problem), High root-zone pH locking out iron, manganese, zinc, boron and copper, Broad mites
- Single-bladed, round or smooth-edged new leavesLikely causes: Light leak or interrupted dark period, Re-vegetation from too-long days in flower
- Short internodes, compact growth and small leavesLikely causes: Hop latent viroid (dudding), Light burn: too much light for the plant's climate and CO2, Cold stress
- Flowering plant pushing new leafy growth instead of budsLikely causes: Light leak or interrupted dark period, Re-vegetation from too-long days in flower
- Seed shell stuck on the seedling's first leavesLikely causes: Seed coat stuck on the cotyledons (helmet head)
- Newest leaves limp while older leaves stay firmLikely causes: Heat stress, Copper deficiency, Boron deficiency
The whole plant
- Whole plant pale or lime greenLikely causes: General underfeeding (whole feed too weak), Nitrogen deficiency, Overwatering (roots short of air)
- Middle leaves yellowing firstLikely causes: Sulfur deficiency, Molybdenum deficiency, Very low pH limiting molybdenum
- Mottled mosaic or yellow streaks, distorted leavesLikely causes: Plant virus (e.g. beet curly top, lettuce chlorosis virus), Hop latent viroid (dudding), Herbicide drift or residue
- Sudden yellowing across the plant within daysLikely causes: Root rot (Pythium), Low dissolved oxygen in the root zone
- Damage only on one side of the plant or one area of the roomLikely causes: Wind burn from a fan blowing directly on leaves, Physical damage (kinks, splits, broken branches), Fusarium wilt or crown rot
- Irregular dead or bleached patches after sprayingLikely causes: Spray or foliar burn (pesticide, oil, soap, foliar feed)
- Dry, torn or curled leaves facing a fanLikely causes: Wind burn from a fan blowing directly on leaves
- Dark, water-soaked lesions on leaves or stemsLikely causes: Botrytis bud rot (grey mould), Humidity too high / VPD too low
- Small raised blisters or corky bumps on leaf undersidesLikely causes: Humidity too high / VPD too low, Overwatering (roots short of air), Oedema (water uptake outrunning transpiration)
- Holes chewed in leaves or ragged edgesLikely causes: Caterpillars and budworms
- Leaves curling down and limp while the pot is wetLikely causes: Overwatering (roots short of air), Humidity too high / VPD too low, Oedema (water uptake outrunning transpiration)
- Leaves held upward, praying, healthy colourLikely causes: Normal leaf movement (praying by day, drooping at night)
- Drooping while the pot is heavy and wetLikely causes: Overwatering (roots short of air)
- Wilting with a light, dry potLikely causes: Underwatering, Dry, water-repellent medium (water runs straight through)
- Wilting even though the root zone is moist, not recovering overnightLikely causes: Root rot (Pythium), Low dissolved oxygen in the root zone, Reservoir or root zone too warm
- Sudden collapse of a hydro or aero plant within hoursLikely causes: Pump, timer, air or emitter failure in a hydro, aero or drip system
- Wilting under the lights that recovers at lights-offLikely causes: Heat stress, Air too dry / VPD too high, Low dissolved oxygen in the root zone
- Cuttings wiltingLikely causes: Cuttings losing water faster than they can root, Air too dry / VPD too high, Fungus gnats
- Drooping or stall right after transplantingLikely causes: Transplant shock, Recovery stall after topping, supercropping or heavy defoliation
- Leaves droop at lights-off and lift in the morningLikely causes: Normal leaf movement (praying by day, drooping at night)
- Purple leaves, bracts or sugar leavesLikely causes: Genetic purple colour (anthocyanin), Normal late-flower fade (senescence), Cold stress
- Very dark green, glossy leavesLikely causes: Nutrient burn (feed too strong), Too much nitrogen, Cal-Mag overuse (excess calcium and nitrogen)
- Bronzed, rusty-looking leaf surfacesLikely causes: Hemp russet mites, Twospotted spider mites, Broad mites
- Dull, grey-green, leathery leavesLikely causes: Sodium build-up (softened water, coco, recirculation), Salt build-up in the root zone, Chloride excess (salinity)
- White powdery spots that wipe off and come backLikely causes: Powdery mildew, Humidity too high / VPD too low
- Grey, fuzzy mouldLikely causes: Botrytis bud rot (grey mould), Humidity too high / VPD too low
- White crust or residue that wipes off and stays goneLikely causes: Hard-water or spray residue, Spray or foliar burn (pesticide, oil, soap, foliar feed), Hard, alkaline water pushing pH up over weeks
- Sticky, shiny leaves (honeydew)Likely causes: Aphids, Whiteflies, Mealybugs
- Black sooty coating on leavesLikely causes: Whiteflies, Aphids, Mealybugs
- White cottony or waxy clumps in leaf axils and stemsLikely causes: Mealybugs
- Yellow patches on top of leaves with grey-purple fuzz underneathLikely causes: Downy mildew
- White crystals or sparkles on leaves and buds that don't wipe offLikely causes: Trichomes or harmless features mistaken for a problem, Thrips
- Musty, mouldy smell in the canopyLikely causes: Botrytis bud rot (grey mould), Humidity too high / VPD too low
- Stretched, thin plant with long gaps between nodesLikely causes: Normal stretch after the flip, Not enough light
- Stunted, slow growth across the plantLikely causes: Overwatering (roots short of air), Autoflower stunted by early stress, General underfeeding (whole feed too weak)
- One plant much smaller than identical siblingsLikely causes: Hop latent viroid (dudding), Weak or slow individual phenotype, Root aphids
- Seedling stalled for over a weekLikely causes: Overwatering (roots short of air), Autoflower stunted by early stress, Fungus gnats
- Autoflower started flowering while still smallLikely causes: Autoflower stunted by early stress, Overwatering (roots short of air), Recovery stall after topping, supercropping or heavy defoliation
- Sudden leaf drop over a day or twoLikely causes: Cold stress
- Fine pale stippling (tiny white or yellow dots) on leaf topsLikely causes: Twospotted spider mites, Thrips, Whiteflies
- Fine silk webbing on leaves, buds or tipsLikely causes: Twospotted spider mites
- Tiny moving dots under the leavesLikely causes: Twospotted spider mites
- Silvery streaks or patches dotted with black specksLikely causes: Thrips
- Clusters of soft, pear-shaped insects on stems or leaf undersidesLikely causes: Aphids
- White flakes (shed insect skins) on leavesLikely causes: Aphids
- Tiny white flies that rise when the plant is shakenLikely causes: Whiteflies
- Caterpillars on leaves or budsLikely causes: Caterpillars and budworms
- Ants on the plantLikely causes: Aphids
- Winding pale trails in leavesLikely causes: Leafminers
- Tiny black specks on leaf surfacesLikely causes: Thrips
- Plant stopped drinking; pot or reservoir level barely dropsLikely causes: Overwatering (roots short of air), Root rot (Pythium), Cold root zone (below about 16 °C / 61 °F)
- Condensation or wet leaves at lights-offLikely causes: Humidity too high / VPD too low, Botrytis bud rot (grey mould)
Buds and flowers
- Dark brown lesions on sugar leaves in flowerLikely causes: Potassium deficiency
- Purple or dark buds in late flowerLikely causes: Genetic purple colour (anthocyanin)
- Single yellow or brown sugar leaf on an otherwise green colaLikely causes: Botrytis bud rot (grey mould)
- Brown, mushy or grey tissue inside budsLikely causes: Botrytis bud rot (grey mould), Caterpillars and budworms
- White powder on buds and sugar leavesLikely causes: Powdery mildew
- Foxtails: new calyx spires growing out of mature budsLikely causes: Heat or light stress foxtailing on the top colas, Heat stress, Cultivar foxtailing (genetic)
- Yellow banana-shaped anthers in the budsLikely causes: Hermaphrodite (herm-prone genetics revealed by stress), Light leak or interrupted dark period, Heat stress
- Pollen sacs (balls) at nodes of a female plantLikely causes: Hermaphrodite (herm-prone genetics revealed by stress), Light leak or interrupted dark period
- Seeds in the budsLikely causes: Hermaphrodite (herm-prone genetics revealed by stress)
- Airy, loose, larfy budsLikely causes: Hop latent viroid (dudding), Not enough light, Heat stress
- Pistils browning early in flowerLikely causes: Heat stress, Heat or light stress foxtailing on the top colas, Light bleaching at the canopy top
- Droppings (frass), webbing or holes in budsLikely causes: Caterpillars and budworms
- Flowering not starting or very slow after the flipLikely causes: Light leak or interrupted dark period, Long-flowering or light-sensitive cultivar
- Bud swell stalls in mid-late flowerLikely causes: Nitrogen deficiency, Re-vegetation from too-long days in flower, Potassium deficiency
- Pinkish-white mould inside budsLikely causes: Fusarium wilt or crown rot
- Brown, crispy bracts or bud tips on the top colasLikely causes: Heat stress, Light bleaching at the canopy top
Roots and root zone
- Brown, soft or sunken stem base or crownLikely causes: Fusarium wilt or crown rot, Root rot (Pythium)
- White fuzz or threads on the medium surfaceLikely causes: Harmless white fungus (mycelium) on organic medium
- White crust on the medium surface or pot edgesLikely causes: Salt build-up in the root zone, Hard, alkaline water pushing pH up over weeks
- Green slime or algae on the medium, roots or in the reservoirLikely causes: Algae from light reaching wet surfaces or the reservoir
- Brown, slimy roots; outer layer slides offLikely causes: Root rot (Pythium), Reservoir or root zone too warm, Low dissolved oxygen in the root zone
- Tan or tea-stained roots that are still firmLikely causes: Harmless root staining (nutrients, tannins, additives), Ammonium toxicity (too much NH4 in the feed)
- Rotten, sour or sewer smell from roots, medium or reservoirLikely causes: Low dissolved oxygen in the root zone, Reservoir or root zone too warm, Root rot (Pythium)
- Thick mat of circling roots at the pot wallLikely causes: Root-bound in a pot too small
- No fresh white root tipsLikely causes: Low dissolved oxygen in the root zone, Chlorine or chloramine in tap water harming roots and soil life, Pump, timer, air or emitter failure in a hydro, aero or drip system
- Short, stubby, brown root tipsLikely causes: Nutrient burn (feed too strong), Salt build-up in the root zone, Copper toxicity (copper sprays, ionisers, pipework)
- White waxy residue and tiny insects on rootsLikely causes: Root aphids, Mealybugs
- Tiny clear larvae with black heads in the mediumLikely causes: Fungus gnats, Overwatering (roots short of air)
- Small black flies around the mediumLikely causes: Fungus gnats, Overwatering (roots short of air), Algae from light reaching wet surfaces or the reservoir
- Reservoir or root zone water warm (above 23 °C / 73 °F)Likely causes: Reservoir or root zone too warm, Pump, timer, air or emitter failure in a hydro, aero or drip system
- Cloudy, foamy or slimy reservoirLikely causes: Algae from light reaching wet surfaces or the reservoir, Reservoir or root zone too warm, Root rot (Pythium)
- Root-zone or reservoir pH climbing steadilyLikely causes: Hard, alkaline water pushing pH up over weeks, High root-zone pH locking out iron, manganese, zinc, boron and copper, Algae from light reaching wet surfaces or the reservoir
- Reservoir pH falling fast without explanationLikely causes: Low root-zone pH starving calcium and magnesium, Ammonium toxicity (too much NH4 in the feed), Root rot (Pythium)
- Reservoir EC rising as the water level dropsLikely causes: Nutrient burn (feed too strong)
- Runoff EC well above input ECLikely causes: Nutrient burn (feed too strong), Salt build-up in the root zone, Sodium build-up (softened water, coco, recirculation)
- Runoff EC much lower than input, or reservoir EC dropping fastLikely causes: General underfeeding (whole feed too weak), Nitrogen deficiency
- Medium stays wet for 4+ days after wateringLikely causes: Overwatering (roots short of air), Humidity too high / VPD too low, Cold root zone (below about 16 °C / 61 °F)
- Medium dries out within a day; water runs straight through or down the sidesLikely causes: Root-bound in a pot too small, Underwatering, Dry, water-repellent medium (water runs straight through)
- White scale on pots, pumps, drippers or the meterLikely causes: Hard, alkaline water pushing pH up over weeks, Cal-Mag overuse (excess calcium and nitrogen)
- Some pots dry while others on the same line stay wetLikely causes: Pump, timer, air or emitter failure in a hydro, aero or drip system
- Reservoir or root zone cold (below 16 °C / 61 °F)Likely causes: Cold root zone (below about 16 °C / 61 °F)
- Water pools on the surface and drains slowlyLikely causes: Overwatering (roots short of air), Root-bound in a pot too small
- Tiny white insects jumping on the medium surfaceLikely causes: Springtails (harmless soil insects)
Stems and branches
- A single branch wilting or dyingLikely causes: Physical damage (kinks, splits, broken branches), Fusarium wilt or crown rot
- Seedling stem pinched and collapsing at the soil lineLikely causes: Damping-off, Fungus gnats, Root rot (Pythium)
- Weak, floppy stems that can't hold the plant upLikely causes: Not enough light, General underfeeding (whole feed too weak), Too much nitrogen
- Kinked, split or snapped stemLikely causes: Physical damage (kinks, splits, broken branches)
- Brown streaks inside the stem when cutLikely causes: Fusarium wilt or crown rot
- Lesions or grey mould on stemsLikely causes: Botrytis bud rot (grey mould)
- Brittle stems that snap easilyLikely causes: Hop latent viroid (dudding), Hemp russet mites
- Purple or red stems and petiolesLikely causes: Genetic purple colour (anthocyanin), Cold stress, Cold root zone (below about 16 °C / 61 °F)
- Excessive stretch after the flip (more than about 3x)Likely causes: Long-flowering or light-sensitive cultivar, Normal stretch after the flip, Not enough light
- Leggy seedling with a long, thin stemLikely causes: Not enough light
