The canopy is the upper surface of foliage formed by all the plants in a space. Light from overhead fixtures is measured at canopy level, and most of the plant's photosynthesis and most of its large buds happen within the top 30-45 cm (12-18 in) or so. Canopy area, the floor area the canopy covers, is also how commercial yields and licences are measured.
In practice
Growers manage the canopy by training (topping, LST, SCROG), by pruning what sits below it, and by setting the light height so PPFD is right at the top: typically about 600-1,000 µmol/m²/s in flower without added CO₂. A dense canopy blocks light from lower branches, which is why the growth beneath it is often lollipopped.
"Canopy temperature" or "leaf temperature" readings come from this layer.
Don't confuse with
- Even canopy: a canopy where all tops sit at the same height.
- Grow area: the tent or room floor; canopy area can be smaller if plants don't fill it.
The process in chloroplasts that uses light energy to turn carbon dioxide and water into sugars and oxygen; cannabis uses the C3 pathway.Yield is the dry weight of usable flower harvested, usually expressed per plant, per square metre of canopy (g/m²) or per watt of light (g/W).LST (low-stress training) bends and ties stems so the plant grows wide and flat, exposing more bud sites to light without cutting or breaking tissue.SCROG (screen of green) trains a few plants under a horizontal net, tucking shoots so the canopy forms a flat, evenly lit layer of many tops.Photosynthetic photon flux density: the number of PAR photons landing on one square metre each second, in µmol/m²/s; the standard measure of light intensity at the canopy.Lollipopping removes the lower branches and small shoots on a plant, usually around the flip, so energy goes to the top buds and airflow improves underneath.Leaf temperature is the actual surface temperature of a leaf, which often differs from air temperature by 1–3 °C depending on light source and transpiration.An even canopy is one where all main tops sit at roughly the same height, so each receives similar light intensity and buds develop more uniformly.Plant density is the number of plants per unit of canopy area; more plants raise yield per area up to a point but shorten veg and reduce uniformity.
