Cold and Chilling Stress

Core science

Low temperature slows enzyme reactions, membrane transport, root growth, respiration, water uptake, and photosynthetic repair. Chilling injury can therefore occur above freezing, while freezing injury involves additional risks associated with ice formation and cellular dehydration.

Cannabis cold response is genotype-, age-, tissue-, duration-, and acclimation-dependent. A controlled hemp study using FINOLA and AutoCBD found that cultivar and plant age altered physiological cold response, and the tested 10-day acclimation treatment at 10 °C did not consistently protect plants; in several outcomes it acted as an additional stress rather than a beneficial hardening treatment.

In that same study, whole plants exposed to short -0.5 °C events and detached leaves exposed to progressively colder temperatures did not support one simple threshold across all measures. Detached leaves showed much greater damage at -8 °C than at -2 or -4 °C, but those detached-leaf results are not universal field or production thresholds for intact plants.

Cold and light interact. Carbon metabolism and photosystem repair slow at low temperature while absorbed radiation can remain high, increasing the risk of excess excitation and photoinhibition. A cold leaf under substantial light can therefore be stressed even when the light level would be tolerated at warmer tissue temperatures.

Cold surfaces can also approach dew point and develop condensation, creating a separate wetness and disease-risk pathway. Droop, discoloration, nutrient-like patterns, marginal necrosis, delayed rooting, and reproductive injury are nonspecific and must be interpreted with temperature history, light, roots, water status, and biological evidence.

Why this matters in cultivation

• Review minimum temperature, exposure duration, cooling and rewarming rate, and plant stage rather than relying on the daily average or frost/no-frost distinction.
• Measure root-zone and irrigation-solution temperature as well as air and leaf temperature because cold roots can remain functionally impaired after room air warms.
• Coordinate light exposure with recovery after chilling instead of assuming that immediately returning to maximum light is always benign.
• Map cold-air supply, exterior walls, floor zones, irrigation lines, door events, and condensation patterns when injury is spatially uneven.

Measure and record

Common misconceptions

Evidence limits and uncertainty

Direct cannabis/hemp cold studies demonstrate strong genotype-, age-, tissue-, acclimation-, intensity-, and duration-dependence. Experimental temperatures from detached leaves or specific hemp cultivars should not be converted into universal injury thresholds for all cannabis germplasm or production systems.

Check your reasoning

• For "Cold and Chilling Stress", explain the mechanism behind this objective: Distinguish chronic cool growth, chilling, freezing, cold-root effects, condensation, and cold-plus-light injury in cannabis without treating one temperature or the absence of frost as a universal diagnostic threshold. Which observation or measurement would best test whether that mechanism is operating in the real crop?
• A learner claims, "No frost means no cold injury occurred." Use the lesson’s science and evidence limits to explain why that claim is unreliable, then name one observation or measurement that could separate the competing explanations.
• Applied case — Review minimum temperature, exposure duration, cooling and rewarming rate, and plant stage rather than relying on the daily average or frost/no-frost distinction. Build a verification plan using the lesson’s record set (Thermal history, Plant context, Light and wetness). What would you compare before and after the action, and what result would make you revise the original interpretation?

Related lessons

Sources and evidence

1. Galic A., Grab H., Kaczmar N., Maser K., Miller W.B., Smart L.B. (2022). Effects of Cold Temperature and Acclimation on Cold Tolerance and Cannabinoid Profiles of Cannabis sativa L. (Hemp). Horticulturae 8(6):531. DOI 10.3390/horticulturae8060531. Direct hemp study of cultivar, age, acclimation, repeated cold exposure, chlorophyll fluorescence, electrolyte leakage, biomass, and cannabinoid responses.
2. Lipidomic remodeling in Cannabis sativa L. under cold tolerance (Industrial Crops and Products, 2025) is used as additional direct-hemp evidence for cold-associated growth, photosynthetic, protective, and membrane-lipid responses; its quantitative findings remain treatment- and genotype-specific.
3. Controlled Volume 14 evidence requires chilling, freezing, acclimation, cold roots, light interaction, and condensation to remain distinct diagnostic mechanisms.