Relative humidity compares water-vapour pressure with the saturation vapour
pressure at that temperature. It is a ratio, not a direct measure of how much
water a leaf contains. Temperature changes the saturation reference, so the
same relative-humidity reading can occur in different atmospheric
conditions.

This is why “we keep humidity at a fixed percentage” is only the beginning of
an explanation. It leaves out temperature, location, timing and what is
happening around the plant.

Vapour-pressure deficit, or VPD, expresses the gap between saturation and
actual water-vapour pressure. In plant discussions, it helps describe the drying
demand of the air. A leaf-to-air calculation also needs leaf temperature; a
calculation based only on room air is not the same measurement.

The practical question is not whether a dashboard shows a fashionable target.
It is whether the readings describe the conditions the plant is actually
experiencing.

A 2025 experiment compared contrasting canopy-humidity conditions in a
CBD-dominant cultivar . The treatments produced differences in flowering
development, biomass and cannabinoid measurements. This supports taking
the environment seriously, but it does not establish a universal setting for
every cannabis cultivar.

It also does not show that one humidity percentage produces a named flavour
in Bloomberry, Orangini or Grapeline. That would require a relevant
comparison and measurements of the outcome being claimed.

Flowa controls temperature and humidity together with light. The aim
includes flavour and consistent quality, rather than yield alone. These are
cultivation priorities, not a guarantee that every flower or every batch will be
identical.

Useful questions include where a reading was taken, whether it represents the
plant canopy, and how conditions change through the day. Asking those
questions is more informative than treating a single room reading as a
complete description of the crop.

A living plant and a dispensed dried flower are different materials. A
discussion of growing-room humidity is not a recommendation to change the
moisture of a medicine at home. For supplied cannabis flower , use the storage
instructions on its packaging and ask the pharmacy if anything is unclear.