Methodology

Short version: published horticultural ranges, narrowed by stage, cross-checked against what real logged grows actually do — and stated as ranges, because cultivars vary.

Environment bands

VPD is computed from temperature and relative humidity: VPD = (1 − RH/100) × SVP, where SVP = 0.6108 × e^(17.27T/(T+237.3)) and T is in Celsius. Leaf temperature typically runs 1–3°C below air temperature under LEDs; where a leaf offset matters we say so and the calculator lets you set it.

Stage bands

Bands are stage-specific because the plant's ability to move water changes: low VPD early (small root mass), higher through veg and flower, driest in late flower to protect dense buds from botrytis. The exact table is on the VPD chart and is the table the app grades against.

Grades

An environment grade is the share of a plant's readings that fell inside its stage band at the time the reading was taken — not an average of averages, and not a comparison to other growers. A grow with few readings gets no grade rather than a misleading one.

What we don't do

• We don't publish yield or potency promises. Genetics listings are reported values from breeders, labelled as such.
• We don't give medical, dosing or legal advice. Growing law varies by jurisdiction and changes; check your own.
• We don't dress guesses as data. Where evidence is thin — flushing is the classic example — we say the evidence is thin.

Aggregate data

Where a page cites what real grows do, the figure comes from published journals in aggregate, never from private accounts, and never in a form that identifies a grower. Sample size is always stated.

Track your own grow free — the journal grades your environment against these bands →