Calyx

The calyx is the first part of the flower that is formed when a young cannabis plant enters its flowering stage. Female cannabis flowers do have calyx cells, but not a defined calyx – in fact, as noted below, the term calyx is often confused with the bract, the visibly swollen part of the flower that contains the potential for a seed.

By definition, a perianth consists of a corolla and a calyx. The female calyx cells are part of the perianth, a veil of tissue that partially encloses the ovule, or the prospective seed. Each female cannabis flower has two stigmas that protrude from a single ovule, which is enclosed by bracts. Stigmas are the pollen catchers. The bracts, with their dense covering of large, stalked resin glands called trichomes, contain the highest concentration of THC of any part of the plant.

Bract vs Calyx

Legendary grower Mel Frank, in a special for Cannabis Business Times on the nomenclature of female cannabis flowers, points out that calyxes are often confused with bracts:

When discussing specific flowering parts, botanical terms are routinely used. And here, confusion reigns. Foremost is the common, incorrect use of calyx. Growers read or hear about swollen calyxes being a sign of maturity and an indication of readiness for harvesting. And growers, touting a favorite phenotype, will refer to its high calyx-to-leaf ratio, meaning that within the buds, flowers predominate leaves. But, what are incorrectly called calyxes or false calyxes are correctly identified as bracts. The correct term should be bract-to-leaf ratio.