Underwatering means the plant runs short of water before the next irrigation. Leaves lose turgor and hang limp and thin, the pot feels very light, and the medium may shrink away from the pot wall. Repeated cycles cause crispy leaf edges, nutrient problems (calcium moves with water), and stunting.
In practice
The fix is to water thoroughly and evenly; very dry peat and coco can repel water at first, so water slowly in stages or bottom-water until they rewet. Plants usually recover within hours. Long term, increase watering frequency, use larger pots, mulch the surface, or move to automated irrigation.
A mild, controlled dry-down is not the same as underwatering. Research found controlled drought late in flower increased cannabinoid concentration, and GenetixBay endorses a mild late drought for cultivars that respond to it, but every cultivar responds differently.
Don't confuse with
- Overwatering: firm, swollen, droopy leaves from wet roots; the pot feels heavy.
- Heat stress: can also cause wilting; check the medium first.
Peat is partially decomposed sphagnum moss from bogs, the base of most potting mixes; it holds water and nutrients well but is acidic and needs lime.Coco coir is a growing medium made from processed coconut husk, prized for holding water and air at once; it binds calcium and magnesium unless buffered.A cannabinoid is any compound that binds the body's cannabinoid receptors or shares the typical cannabis terpenophenolic structure; the plant-made ones are phytocannabinoids such as THCA and CBDA.Overwatering is watering so often that the medium stays saturated, starving roots of oxygen, which causes drooping, slow growth and root disease.Heat stress is damage or slowed growth when leaf or canopy temperature rises above what the plant can handle, typically above about 30–32 °C (86–90 °F) in cannabis.The wet-dry cycle is the alternation between watering a container and letting it dry back, which refreshes oxygen in the root zone between irrigations.Dryback is the drop in a substrate's water content between irrigations, usually expressed as a percentage of its content at full saturation.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.
