Bud rot shows up first as a small brown or gray patch on one section of a bud, often tucked at the stem where you cannot see it from above. The sugar leaves around that spot turn yellow, then curl and die while the rest of the cola still looks green. Check the top of every cola and the inside of your densest buds once a day during the last four weeks of flower.

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What are the first visible signs of bud rot?

Botrytis cinerea, the fungus behind bud rot, grows from the inside out. By the time gray fuzz reaches the surface, the infection has already eaten through the stem tissue that feeds the flower. That is why early detection depends on color changes and leaf behavior, not just mold.

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Leaf clues

• Sugar leaves around one small section turn yellow or brown while the rest of the cola stays green.
• Those leaves wilt, curl at the tips, or pull away from the bud with no resistance.
• A single fan leaf on one branch goes limp days before harvest.
• Leaves look wet or greasy even when room humidity sits in range.

Bud clues

• A patch of calyxes turns dull brown, tan, or gray instead of the strain's normal color.
• The spot looks sunken or collapsed next to healthy tissue.
• A faint gray or white fuzz appears when you bend the bud toward a light.
• The bud feels light or hollow when you give it a squeeze.

What does bud rot smell like?

Smell is the fastest tell. Healthy cannabis at week seven carries terpenes: citrus, pine, fuel, or earth. Bud rot adds a musty, basement, wet-cardboard note that gets stronger when you open the tent or the jar.

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At later stages the odor turns sharp and ammonia-like. If a jar of cured flower hits you with that smell when you crack the lid, treat the whole jar as suspect and check it bud by bud.

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How do you inspect a plant without spreading spores?

1. Wash your hands and change gloves between plants. Spores travel on fingers and tools.
2. Work from the healthiest plants to the most suspect plants, never the reverse.
3. Tilt each cola toward a bright light and check the stem junction first.
4. Pull the bud apart at the base with two fingers. Rot hides where stem meets flower.
5. Snap the main stem of a suspect cola. A brown or hollow core is a strong sign.
6. Drop anything you remove into a sealed bag, not on the floor or in compost.
7. Wipe scissors and snips with isopropyl alcohol between cuts.

Which conditions raise the risk?

Botrytis needs moisture on plant tissue for several hours plus cool temperatures to germinate. Indoors, that means a humidity spike during lights-off, when air cools and relative humidity climbs past 60%. Outdoors, fog, rain, and morning dew do the same thing.

• Relative humidity above 55% to 60% during late flower.
• Buds packed against each other with no airflow between colas.
• Temperatures between 59 and 75 F, the band where Botrytis grows fastest.
• Overhead watering or foliar sprays late in flower.
• Dead leaves left inside the canopy.
• Dense indica-dominant colas, which dry slower than airy sativa flowers.

How do you tell bud rot from other bud problems?

• Powdery mildew: white powder on leaf surfaces that wipes off, with no brown core.
• Spider mites: fine webbing and speckled leaves, but no gray fuzz or mushy tissue.
• Nutrient burn: brown leaf tips across the whole plant, not one patch inside a bud.
• Light burn: bleached, crispy tops near the lamp, dry rather than mushy.
• Bud rot: brown or gray patch inside the flower, soft texture, gray fuzz, musty smell.

What should you do the moment you find bud rot?

Cut the affected cola off below the infection and seal it in a bag. Do not compost it and do not smoke it. Botrytis can produce mycotoxins, and mold spores in your lungs are a real health risk.

• Remove the whole branch, not just the visible spot. The fungus runs ahead of what you can see.
• Add airflow and drop humidity to 45% to 50%. Aim fans at the canopy wall, not at the buds.
• Harvest early if rot keeps spreading. A slightly early harvest beats a lost crop.
• Inspect every plant the same day, then again 48 hours later.
• Sanitize the tent, fans, and tools after harvest.

Does bud rot always show on the outside?

No. Early infections often start at the stem and stay hidden under healthy-looking calyxes. That is why squeezing buds and checking stem junctions matters more than a visual scan from above.

Can you save a bud with a small brown spot?

You can save the plant, not that bud. Cut the spot plus two inches of surrounding tissue and watch the branch for new symptoms over the next three days.

Is bud rot dangerous to smoke?

Yes. Moldy flower can carry spores and mycotoxins that irritate lungs and trigger allergic reactions. Throw it out.

How do you prevent bud rot after the first catch?

• Keep late-flower humidity between 40% and 50% with a dehumidifier and a controller.
• Run oscillating fans around the clock, but never point them straight at colas.
• Defoliate the bottom third and any leaf that shades a bud site.
• Space plants so each cola gets its own column of air.
• Water at the base, in the morning, and stop before runoff sits in the saucer.
• Check buds every day for the last four weeks before harvest.

What should you check when you buy legal flower?

Licensed US shops test cannabis for mold and yeast under state rules, but a visual check still helps. Ask for a harvest date, since older flower sits longer and carries more risk.

• Look for brown patches, dull gray fuzz, or dark spots near the stem before you pay.
• Smell the jar if the shop allows it. Musty or ammonia notes mean walk away.
• Skip flower with a spongy, collapsing feel. Good bud springs back.