Short answer
Give outdoor cannabis at least 6–8 hours of direct sun a day, and as much more as the site allows. Clear summer days deliver roughly 40–60 mol/m²/day of light, above most indoor flower rooms, and yield rises with every extra hour of direct sun. Supported for the light–yield link; the hour count is Grower practice.
Why
More light, more grams. In two controlled trials, flower yield rose in proportion to canopy light from 120 to 1,800 µmol/m²/s, with no change in potency per gram [1][2].
Outdoor light is generous but variable. Daily light integral changes with month, latitude and cloud; monthly maps show midsummer values far above winter ones across the United States [3].
Shade costs twice. Shaded plants make less and airier flower, and leaves and buds stay wet longer after dew or rain, which favours mildew and rot [4].
Light, not heat, is the goal. Midday summer sun reaches about 1,500–2,000 µmol/m²/s; the risk in hot climates is root and leaf heat, not the light itself.
The numbers
| Direct sun per day | What to expect |
|---|---|
| 8 h or more | Full-size plants, dense buds |
| 6–8 h | Good results, somewhat smaller |
| 4–6 h | Smaller plants, airier buds |
| Under 4 h | Thin, airy buds; consider another site |
| Measure | Typical value |
|---|---|
| Midday summer sun | ~1,500–2,000 µmol/m²/s |
| Clear midsummer DLI | ~40–60 mol/m²/day |
| Indoor flower target (for comparison) | 35–56 mol/m²/day at 800–1,200 µmol/m²/s |
What to do
- Watch your site through a full sunny day in early summer and count direct-sun hours.
- Prefer sites open to the south and east (north and east in the Southern Hemisphere).
- Use containers if you need to move plants to follow the sun.
- Prune overhanging branches before planting.
- Harden indoor-raised plants off over 7–14 days.
- In very hot climates, give roots shade and mulch, not the leaves.
Common mistakes
- Judging a site in spring, before trees leaf out.
- Planting in a damp, shaded corner where buds never dry.
- Moving plants from a tent straight into midday sun.
Related
- Full article: PPFD and DLI by stage, with the evidence
- Answers: Bigger, denser buds · Why buds are airy · Start indoors, move outside
- Terms: DLI · outdoor growing
