Mould on cannabis flower: how to spot it

Why this matters in Thailand

Average humidity in Thailand sits above the right range for storing flower for most of the year. Flower left in a bag that does not seal, in a room with no humidity control, can develop mould within days.

Checking by eye

Most mould looks like a white or grey-green film — powdery, or fine web-like strands sitting on the surface. Look hardest at the inside of dense buds and around the stem, where air moves least.

The usual confusion is with trichomes, the tiny crystals that occur naturally on flower. Trichomes are clear or milky, with a stalk and a round head, and under a loupe the shape is obvious. Mould is filament-like with no regular structure.

Checking by nose

Smell is a very reliable signal. Mouldy flower smells musty — like a cellar, wet grass, or faintly of ammonia. That smell overrides the strain's own. If you open a jar and the first thing you get is must, that is your warning.

If you find mould

Do not use it, and do not try to pick out the visible part. The filaments run further into the flower than what you can see. Heating it does not make it safe.

Inhaling mould spores can cause respiratory symptoms, particularly for people who are immunocompromised or have an existing lung condition. If you feel unwell after use, see a doctor.

Prevention beats detection

Prevention is humidity control from the start — see the storage guide. If you buy a larger amount, split it across several small jars rather than repeatedly opening one big one, since the humidity shifts every time it is opened.