Stigma

The stigma is the receptive surface of the pistil, where pollen grains land and germinate. In cannabis each pistillate flower has two long, thin stigmas, usually white or cream (sometimes pink or purple), emerging in a V from the tip of the bract. A pollen tube grows from the grain down to the single ovule.

In practice

Receptive stigmas are fresh, white and extended. A breeder pollinates when a branch is covered in fresh stigmas, typically in the first two to four weeks of flower. Once fertilised, the stigmas of that flower wither and brown within days, which is one way to see that pollination worked.

On unpollinated plants stigmas keep coming for weeks, then gradually darken and recede. Colour change also follows heat, low RH, physical handling and spraying, so stigma colour alone is a poor harvest clock.

Don't confuse with

• Pistil: the whole female organ; the stigma is its tip.
• Trichome: resin gland on the bract surface, not a hair from the ovary.
• Pre-flower: the first individual flower, identified by its stigmas.