The wet-dry cycle describes how a container moves from saturation after watering, through drainage and plant uptake, to drier conditions before the next watering. As water leaves the pores, air replaces it, and roots get fresh oxygen. Roots also grow towards moisture, so moderate drying encourages them to explore the pot.
In practice
In soil, the classic advice is to water to runoff, then wait until the pot is light (often when the top 2-3 cm, about 1 in, is dry) before watering again. Lift the pot to learn its wet and dry weight. In coco and rockwool, the cycle is shorter and measured as dryback, the percentage of water content lost between irrigations; crop steering uses the size of that dryback deliberately.
Too wet too often suffocates roots; too dry wilts the plant. The ideal size of the cycle depends on medium, pot size and stage.
Don't confuse with
- Dryback: the measured drop in substrate water content in a single cycle; a quantified wet-dry cycle.
- Drought stress: deliberate or accidental extended drying.
Runoff is the water or nutrient solution that drains out of the bottom of a container after irrigation; growers test it to see what is happening in the root zone.A large palmate cannabis leaf with several long leaflets on a long petiole; fan leaves do most of the plant's photosynthesis and carry few trichomes.Watering to runoff means applying enough water or solution that some drains from the bottom of the container, typically 10-20% of the volume applied.The weight of cannabis after drying (and usually trimming), the basis growers use for yield; it is typically about 20-25% of trimmed wet weight.Dryback is the drop in a substrate's water content between irrigations, usually expressed as a percentage of its content at full saturation.The amount of water in a material as a percentage of its weight; cured cannabis flower usually sits around 10-12% w/w, though measurement method matters.Drying cannabis below the target water activity (under about 0.55), leaving buds brittle and harsh, with lost terpenes; rehydrating does not restore them.Pot size is the volume of medium a plant roots into; bigger pots give bigger plants within reason, but feeding frequency can let small pots punch well above their size.Overwatering is watering so often that the medium stays saturated, starving roots of oxygen, which causes drooping, slow growth and root disease.Underwatering is letting the medium dry too far between waterings, so the plant loses turgor and wilts, with limp, papery leaves and crisping edges if repeated.Field capacity is the amount of water a medium holds after it has been saturated and allowed to drain freely; in pots it is called container capacity.Crop steering adjusts irrigation timing, volume and dryback, along with climate, to push plants towards vegetative growth or generative (flowering) growth.
