Bud Rot

Bud rot is Botrytis cinerea, a gray mold that starts deep inside a dense bud where moisture sits and air does not move. By the time you can see it from outside, the inside of that bud is already gone.

What you are seeing#

The first sign is almost never mold. It is a single sugar leaf in the middle of an otherwise healthy cola, gone yellow or brown and dried up while everything around it is green. It pulls out with no resistance at all.

That is your cue to open the bud. Pinch it gently and pull it apart at that spot. Inside you will find gray fuzz, tissue gone soft and stringy like wet felt, and a brown mushy core. Advanced spots smell musty, like a damp basement.

From outside, an affected cola develops brown patches, the pistils there brown and shrivel early while the rest of the plant is still white, and the bud feels damp or spongy when everything else is firm.

Check the biggest, densest colas first, then the middle of the plant. Check daily in the last 3 weeks of flowering. Bud rot also appears during drying if the room runs above 60 percent humidity.

Why it happens#

Moisture trapped inside dense flower with no air movement. Botrytis spores are already present in almost any grow space and only need the conditions: humidity above 55 percent during flowering, a big temperature drop at lights off that condenses moisture onto the buds, too little exhaust, a canopy so dense the inner colas never dry, spraying anything onto buds, and tight indica-leaning genetics. Outdoors, a stretch of rain in late flower does it almost every time.

How to fix it#

1. Cut it out now, today. Use clean shears and cut the stem 2 to 4 inches below the visible rot, into clearly healthy tissue. Rot spreads down the stem before it shows.
2. Do not shake the plant while you do it. Hold a bag under the bud and cut into the bag. Disturbing a rotted bud releases a cloud of spores onto every other cola in the tent. Sterilize the shears with isopropyl between cuts.
3. Drop humidity to 40 to 45 percent immediately and increase exhaust.
4. Keep the lights-off temperature drop under 10F. A large drop pushes relative humidity up sharply at exactly the wrong time.
5. Defoliate the inner canopy so air reaches the middle of every plant, and add a circulation fan aimed through, not at, the buds.
6. Inspect every cola every day for the rest of the grow. A second spot usually appears within days of the first.
7. Do not spray anything. No fungicide belongs on flowering buds, and wetting them makes it worse.
8. If more than a quarter of the plant is affected, harvest early. A slightly immature harvest you can smoke beats a ripe one you throw out.
9. Dry at 60F and 60 percent humidity with air moving, and check jars daily through the first week of curing.

How to tell it apart#

Versus powdery mildew. Mildew is white, sits on the outside surface, and wipes off with a finger. Bud rot is gray, grows from the inside out, and the bud is brown and mushy at the core. Open the bud: that is the only test that settles it.

Versus light burn. Light burn bleaches the highest buds white or pale yellow, but the tissue stays dry and firm and the damage is strictly on the side facing the lamp. Bud rot happens inside and in the middle of the plant, and the tissue is soft. Squeeze it: firm and dry is light burn, damp and spongy is rot.

Versus hermaphrodite plants. A bud swelling with seeds also looks and feels wrong, and beginners open one and assume the worst. Seed pods are hard, round and green or tan, sitting in the calyxes with healthy tissue around them. Bud rot is gray, soft and dead. A seeded bud is smokeable. A rotted one is not.

How long until it looks better#

It does not, and this is the page where that matters most. Bud rot does not recover. Removed bud is gone, and that weight is simply lost from your harvest.

What you can change is whether it spreads. With humidity at 40 to 45 percent, good airflow and daily inspection, you should find no new spots after 3 to 5 days. If you keep finding rot every day for a week, the environment is not actually fixed or the plant is too dense to save, and harvesting early is the right call.

The real answer is next grow: fewer plants in the space, more exhaust, a hygrometer at canopy height, and defoliation before flowering.