10 Common Cannabis Symptoms and What They Actually Mean

3 min read

A reference grid of ten common cannabis leaf symptoms from drooping to white powdery mildew

Not an encyclopaedia. The ten things that send people to Google at midnight, with what each one probably is and what to do first. Keep the order in mind the whole way down: environment, water, pH, nutrients.

The short version:

  • Most symptoms are environment or watering, not deficiencies
  • Damaged leaves don’t heal — you’re judging the fix by the new growth
  • One yellow lower leaf is rarely an emergency
  • White powder or grey fuzz is the one exception — act now, don’t wait

Want the full breakdown? Keep scrolling.

The ten symptoms

Drooping, whole plant wilted. Over- or underwatering. Lift the pot. Heavy means she’s drowning — leave her till it’s light. Light means thirsty — water her. Stop watering on a schedule.

Yellowing lower leaves, bottom up. Normal in late flower (she’s feeding the buds). In early veg and spreading, she may want more nitrogen — check pH first, then nudge the feed.

Tip burn, crispy brown leaf tips. Too much food. Back off 25%, water plain next time. Burnt tips won’t recover; new growth should come clean.

Leaf curl, edges up like a taco. Heat or light stress. Above 28°C at the canopy, or light too close. Raise the light, improve airflow.

Purple stems. Often just genetics or cool nights (below 15°C). Only suspect phosphorus if the leaves are affected too. Otherwise ignore it.

Slow growth, stalled. Three usual causes: root-bound (check for circling roots), pH out of range, or not enough light. Occasionally compacted soil.

Spots, irregular marks. Brown-with-yellow-halo on lower-mid leaves leans calcium — check pH first. Holes or a pattern, or random with no pattern — get the loupe out and check for pests.

Stretching, tall and spindly. Not enough light, or it’s too far away. Move it closer within the maker’s limits. New growth tightens up.

Crispy leaf edges. Low humidity (below 35–40%) or a fan blasting one spot. Fix whichever it is.

White powder or grey fuzz. Mould. This is the one where you act immediately — powdery mildew gets affected leaves cut and bagged, humidity dropped, airflow up; grey fuzz in a bud is bud rot, cut the whole bud out. Don’t google it. Act.

How do I use this without panicking?

Pick the symptom, take the first action, change one thing, then wait 48–72 hours and watch the new growth. A tenner loupe (DIG stock them) settles the pest-or-nutrient calls. Most of the time the plant isn’t dying — it’s just talking to you, slowly.

FAQ

Which symptom should I never wait on? White powdery mildew or grey bud rot. Every other symptom rewards patience; mould rewards speed. Remove and treat the moment you see it.

My leaf tips are brown and crispy — what is it? Usually nutrient burn from feeding too strong. Cut the strength by a quarter and water plain next feed. Judge it by the next leaves, not the burnt ones.

Are purple stems a problem? Usually not. Many strains do it, and cool nights bring it out. Only worry if the leaves themselves show phosphorus symptoms too.

More like this