A quick-reference dictionary for home growers. Master the science of lighting metrics, rootzone biology, environmental pressure scales, and structural plant training methods.
The total amount of photosynthetically active radiation (PAR) that lands on a specific surface over the course of a 24-hour day, measured in moles per square meter per day (mol/m²/d).
Controls the plant's growth speed. Seedlings need 10–15 DLI, vegetative plants need 30–45 DLI, and flowering plants need 40–55 DLI for maximum yields.
The measurement of light intensity landing on a specific spot per second, specifically within the PAR waveband (400–700nm). Measured in micromoles per square meter per second (µmol/m²/s).
Growers adjust light height and dimmers based on PPFD targets: e.g., 200 µmol for seedlings, 600 µmol for veg, and 800+ µmol for bloom.
The difference between the humidity pressure inside the leaf's stomata (which is 100% saturated) and the relative humidity pressure of the surrounding air. Measured in kilopascals (kPa).
Dictates how hard the plant is 'sweating' (transpiring). Low VPD stalls transpiration and causes calcium lock; high VPD dries the plant, causing stomata to close and growth to stall.
A numeric scale (0–14) indicating the acidity or alkalinity of water or grow medium. 7.0 is neutral; lower values are acidic, higher are alkaline.
Roots can only absorb nutrients at specific pH windows. Soil requires 6.0–6.8 pH, while coco/rockwool/hydro setups require 5.5–6.2 pH.
The measurement of water's ability to conduct electricity, which indicates the concentration of dissolved mineral salts (fertilizer strength) in the solution. Measured in milliSiemens per centimeter (mS/cm).
Tells you exactly how strong your feed water is. Runoff EC also indicates if salts are accumulating inside the soil/coco rootzone.
The three primary macronutrients required by plants. Nitrogen (N) drives green vegetative foliage; Phosphorus (P) supports roots and flower buds; Potassium (K) drives overall cell vigor and starch synthesis.
NPK ratios printed on fertilizer labels indicate their strength. Veg feeds use high N (e.g. 9-3-6), while bloom feeds switch to high P & K (e.g. 2-8-4).
A foundational secondary nutrient supplement. Calcium builds strong plant cells and vascular pathways; Magnesium forms the central core of chlorophyll molecules needed for photosynthesis.
Crucial for coco coir setups (which bind calcium chemically) and reverse osmosis (RO) water filtration.
A technique involving gently bending and tying down branches to keep the plant canopy flat and even, without wounding or cutting the plant itself.
Distributes growth hormones equally so that side branches receive as much light as the main stalk, replacing one central bud with dozens of colas.
Training methods that involve wounding or removing parts of the plant, such as super-cropping (crushing inner stems to bend them) or topping/FIMing.
Used to radically shape plant structures and manage height in small spaces. Done strictly during the vegetative stage.
The act of cutting off the main stem's growth tip between leaf nodes, forcing the plant to develop two main growth stalks instead of one.
Breaks apical dominance, redistributing growth hormones to side nodes to encourage a bushier structure.
A pruning technique where 80% of the very tip of a new shoot is pinched or cut, leaving a small rosette of growth.
Less stressful than topping; results in 3 to 4 main colas growing from the single cut site rather than two.
Mushroom-shaped glands that secrete resin containing cannabinoids (THC, CBD) and terpenes on the surfaces of flowers and sugar leaves.
The indicator for harvest. Clear heads mean unripe; milky white heads indicate peak THC; amber heads indicate THC is degrading into CBN (couchlock effect).
Cannabis strains that rely on changes in daily light cycles to trigger the flowering phase. They remain vegetative under 18+ hours of light, and bloom under 12 hours of light.
Requires lightproof grow spaces. Any light leaks during the 12-hour dark cycle can stress the plant, causing it to reveg or hermie.
Cannabis strains crossed with Cannabis Ruderalis genetics, causing them to flower automatically based on age (usually 3–4 weeks from seed) regardless of photoperiod light cycles.
Very fast harvest cycles and highly resilient, but leaves no time to recover from training mistakes or transplant shock.
The drainage water that exits the bottom of the container after feeding.
Testing runoff pH and EC is critical to diagnose root zone nutrient lockouts or salt toxicities before leaves show damage.
Feeding plain, pH-adjusted water with zero nutrients during the final 7–14 days before harvest.
Forces the plant to consume its stored nutrient reserves, reducing excess nitrogen and chlorophyll to yield smoother smoke and white ash.
A hydroponic growing method where plant roots are suspended in a highly oxygenated, nutrient-rich water reservoir using air stones.
Ideal for rapid vegetative growth and high nutrient uptake, though requires strict water temp control to prevent root rot.
A hydroponic system that temporarily floods the root zone with nutrient solution, then drains it back into a reservoir.
Prevents root suffocation while ensuring constant nutrient absorption. Excellent for multi-pot systems.
A hydroponic technique where roots are suspended in air and misted continuously or intermittently with a fine nutrient solution.
Provides maximum oxygen absorption for extreme root growth, widely used in automated commercial cloning.
A biodiverse soil mix rich in beneficial fungi, bacteria, protozoa, and micro-arthropods that break down organic matter to feed plants.
Focuses on feeding the soil biology, which in turn feeds the roots, eliminating the need for synthetic liquid feeds.
A heavily pre-amended potting soil layer placed at the bottom of containers to support organic, water-only grow cycles.
Allows growers to achieve organic harvests by simply watering with plain water throughout the cycle.
Beneficial symbiotic fungi that colonize plant roots, extending their reach to absorb water and nutrients (especially phosphorus) in exchange for plant sugars.
Drastically improves transplant success, root health, and nutrient absorption efficiency.
Fast-growing companion plants (like clover or vetch) seeded in living soil to protect the topsoil, capture atmospheric nitrogen, and feed soil microbes.
Keeps the soil food web alive between runs and prevents erosion.
A liquid soil amendment brewed by aerating organic compost, worm castings, and molasses in water to multiply beneficial aerobic microbes.
Used as a soil drench or foliar spray to boost root health and prevent leaf pathogens.
The observable physical characteristics of a plant (height, smell, leaf shape, bud structure) determined by the interaction of its genetics and environment.
Growers select outstanding phenotypes ('phenohunting') to clone and propagate as mothers.
The complete genetic makeup of a seed or plant, inheriting genes from its parent strains.
Different seeds from the same pack share the same genotype ancestry, but will manifest as distinct phenotypes.
A pure, indigenous cannabis strain that has naturally adapted to a specific geographic region (e.g. Thai, Afghani, Hindu Kush) over centuries without human hybridization.
Prized by breeders for their stable genetics and pure cannabinoid/terpene expressions.
A breeding technique where a hybrid offspring is crossed back with one of its original parents to stabilize desirable traits.
Ensures offspring seeds consistently express specific parent traits like aroma or pest resistance.
Chemical compounds (like THC, CBD, CBG) secreted by flower trichomes that interact with human cannabinoid receptors.
Directly dictates the medicinal and psychoactive effects of the harvest.
Aromatic organic compounds found in cannabis trichomes that give strains their unique smells (lemony, piney, earthy) and modulate the cannabinoid high (Entourage Effect).
Terpenes dictate aroma profiles and guide physiological sensations (e.g., Myrcene causes sleepiness).
A cannabis plant that develops both female pistils and male pollen sacs due to genetic predisposition or environmental stress.
Must be removed immediately to prevent pollen release, which seeds the entire female flower crop.
A high-stress training method where the inner woody fibers of a stem are bent and crushed without breaking the outer skin, forcing the branch to knuckle and grow horizontally.
Creates a massive vascular knuckle that increases nutrient flow and bends tall branches back into the light canopy.
A training method using a flat horizontal trellis net or screen positioned above the canopy. Branches are tucked under the screen as they grow.
Forces the plant to grow horizontally, ensuring every single bud site is aligned in the optimal light zone.
A method focusing on growing a high density of small plants (often clones) in small pots, transitioning them to flower early to harvest one single main cola per plant.
Optimizes space utilization and reduces vegetative time for rapid turnarounds.
A state where plants cannot absorb nutrients, usually due to salt build-up in the medium or incorrect water pH levels.
Requires flushing the rootzone with pure pH-adjusted water to dissolve salts and reset root health.