# Damage only on one side of the plant or one area of the room: likely causes and fixes

> Damage only on one side of the plant or one area of the room on cannabis is most often Wind burn from a fan blowing directly on leaves, Physical damage (kinks, splits, broken branches) or Fusarium wilt or crown rot. How to tell them apart, the fix for each and what recovery looks like.

Also called: only one side affected, damage near the fan, one corner of the tent, problem only by the light edge.

Run the checker with this sign: https://genetixbay.com/knowledge/diagnose/?at=whole&s=damage-one-side

## Likely causes, most likely first

### Wind burn from a fan blowing directly on leaves (Likely)

- Kind: Environment; urgency: Low urgency
- Fix: Aim fans across and under the canopy, not straight at leaves: leaves should rustle, not thrash (roughly 0.3-1.0 m/s at leaf level). Damaged leaves stay damaged. Cannabis-specific evidence is grower observation.
- Recovery: No new damage on the fan side within a week.
- Confirm: Compare with siblings or the same cut: Put the affected plant beside siblings or clones of the same cut in the same conditions. A trait shared by all of a cultivar (purple stems, foxtailing, pale colour) is genetic; a problem on one plant points to its roots, a virus or its genetics; a problem on every cultivar points to the environment or feed.
- Article: [Airflow: air exchange, canopy air speed and fan placement](https://genetixbay.com/knowledge/environment/airflow.md)

### Physical damage (kinks, splits, broken branches) (Less likely)

- Kind: Physical damage; urgency: Deal with it this week
- Fix: Splint and tape a split stem within hours (tape, plant tie or a straw splint); a supercropped knuckle heals stronger in 3-7 days. Remove fully broken branches with a clean cut. Support heavy colas with a trellis.
- Recovery: Leaves above the wound regain turgor within 1-2 days; a callus forms within a week.
- Confirm: Cut a wilting stem lengthwise: On a wilting or dying branch, scrape the lower stem and cut it lengthwise with a clean blade. Brown streaks in the water-conducting tissue point to vascular wilt (Fusarium). A dark, sunken crown points to crown rot. Disinfect the blade afterwards.
- Article: [HST and supercropping: controlled stem crushing](https://genetixbay.com/knowledge/training/hst-supercropping.md)

### Fusarium wilt or crown rot (Less likely)

- Kind: Disease; urgency: Act within a day or two
- Fix: No cure once infected: remove the plant with its medium in a bag, sanitise pots, trays and water lines, and use clean clones and new media. Reduce root stress (overwatering, heat, salts) on the rest.
- Recovery: No further wilting plants over the next 2-3 weeks.
- Confirm: Cut a wilting stem lengthwise: On a wilting or dying branch, scrape the lower stem and cut it lengthwise with a clean blade. Brown streaks in the water-conducting tissue point to vascular wilt (Fusarium). A dark, sunken crown points to crown rot. Disinfect the blade afterwards.
- Confirm: Send a sample to a plant diagnostic lab: For rots, wilts, leaf spots and viruses you can't separate by eye, send a fresh sample (whole plant with roots or a wilting branch with healthy and diseased tissue) in a sealed bag to a university or commercial plant diagnostic clinic. Results in days to 2 weeks.
- Confirm: Look at the roots: Hydro: lift the net pot and look at the root mass in good white light. Containers: tip the plant out with a hand over the medium and look at the edges and bottom of the root ball. Healthy roots are white to cream with fine fuzzy tips. Brown roots whose outer layer slides off between the fingers leave a bare thread: rot. Firm, evenly tan roots with white tips in coloured solution are staining.
- Article: [Fusarium in cannabis: wilt, crown rot and bud rot](https://genetixbay.com/knowledge/diseases/fusarium.md)

### Herbicide drift or residue (Less likely)

- Kind: Physical damage; urgency: Deal with it this week
- Fix: Outdoors or with contaminated compost, manure or straw (persistent herbicide residues). Remove the source, repot into clean media; new growth may normalise slowly. Cannabis-specific symptom descriptions are scarce.
- Recovery: New growth normalises over 2-4 weeks after the source is removed.
- Confirm: Magnifier check of leaf undersides and new growth: Use a 10-20x loupe for spider mites, thrips, aphids and whiteflies, and a 30-60x lens or clip-on phone macro for broad and russet mites. Check the undersides of 10 affected leaves across several plants and the newest shoot tips, in white light. Look for moving dots, eggs, shed skins, webbing, slender insects with black specks, and glassy specks on new growth.
- Confirm: Send a sample to a plant diagnostic lab: For rots, wilts, leaf spots and viruses you can't separate by eye, send a fresh sample (whole plant with roots or a wilting branch with healthy and diseased tissue) in a sealed bag to a university or commercial plant diagnostic clinic. Results in days to 2 weeks.
- Article: [Why are my cannabis leaves curling? The master curling and clawing decision tree](https://genetixbay.com/knowledge/diagnosis/curling-clawing-decision-tree.md)

## Note

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.