Cannabis Grower’s Glossary: Terms Every Indoor Cultivator Should Know

Indoor cannabis cultivation is part science, part art - and like any craft, it comes with its own language. Whether you're just setting up your first grow tent or dialing in an advanced hydro setup, this glossary breaks down the key terms every indoor grower needs to know. From lighting and nutrients to training techniques and troubleshooting, we’ve compiled the definitive reference for navigating your grow room with confidence.

A–C: From Airflow to Clones

Air Exchange

The process of replacing stale air in your grow space with fresh air from outside. Crucial for controlling temperature, humidity, and CO₂ levels.

Auto-flowering

A type of cannabis that switches from vegetative growth to flowering based on age - not light cycle. Popular with beginners and small grow setups due to shorter grow times.

Ballast

A device that regulates current to HID (High-Intensity Discharge) grow lights. Digital ballasts are quieter, more efficient, and adjustable compared to magnetic versions.

Bud Site

Location on the plant where flowers (buds) form. Encouraging more bud sites leads to higher yields - especially with proper training.

Canopy

The uppermost layer of leaves and buds in a grow. A flat, even canopy is key for maximizing light distribution indoors.

Carbon Filter

A cylindrical filter filled with activated carbon, often paired with an exhaust fan. Used to trap odors and keep your grow discreet.

Chlorosis

Yellowing of the leaves due to nutrient deficiencies, pH imbalances, or overwatering. Often the first visible sign that something’s wrong.

Clone

A genetic copy of a cannabis plant taken from a cutting. Cloning allows growers to preserve desirable traits and skip the seedling stage.

D–H: Dialing In Your Grow

DLI (Daily Light Integral)

A measurement of total light (in moles) your plant receives per day. Important for matching light intensity and duration to your plant’s stage.

EC (Electrical Conductivity)

Measures the concentration of nutrients in your water solution. Essential for hydroponics and coco growers to avoid under- or overfeeding.

Feminized Seeds

Seeds bred to produce only female plants - important for indoor growers focused on flower production without accidental pollination.

Flush

The practice of giving plants plain water (no nutrients) for a set time before harvest. Helps remove excess salts and improve taste/smoothness of the final product.

Grow Medium

The material your roots grow in - such as soil, coco coir, perlite, or hydroton. Each medium has different water and nutrient retention characteristics.

HID (High-Intensity Discharge)

A type of grow light including Metal Halide (MH) and High-Pressure Sodium (HPS). Still widely used but gradually replaced by LEDs for energy efficiency and control.

Humidity Dome

A clear cover used to maintain high humidity for seedlings and clones. Prevents moisture loss while roots develop.

I–N: Lighting, Nutrients, and More

IPM (Integrated Pest Management)

A holistic, layered approach to pest control involving prevention, monitoring, and minimal chemical use. Key in sealed indoor environments.

LED (Light-Emitting Diode)

Modern indoor grow lights with lower heat output, full-spectrum capabilities, and customizable intensity. Popular for energy savings and precision.

LST (Low Stress Training)

A technique of gently bending and tying down stems to promote more even growth and increase light penetration to lower bud sites.

Node

The area where branches and leaves meet the main stem. Node spacing is often an indicator of light intensity and plant health.

NPK Ratio

The concentration of Nitrogen (N), Phosphorus (P), and Potassium (K) in your fertilizer. Different stages of growth require different NPK balances.

O–S: Optimization and Structure

PGRs (Plant Growth Regulators)

Synthetic or natural chemicals used to influence plant growth. Some synthetic PGRs are banned or frowned upon for health and safety reasons.

pH (Potential Hydrogen)

A measure of acidity or alkalinity in your water or grow medium. For most indoor cannabis grows, a pH of 5.5–6.5 is ideal depending on the medium.

Photoperiod

The light schedule controlling a cannabis plant’s growth stages. Indoor growers manipulate photoperiods to control when plants flower (e.g., 18/6 veg, 12/12 flower).

PPFD (Photosynthetic Photon Flux Density)

A measurement of light (in µmol/m²/s) available to the plant. Essential for optimizing light intensity across your canopy.

Reservoir

A container that holds nutrient-rich water, typically for hydroponic or automated drip systems.

Runoff

Water that drains from the bottom of your pots. Measuring its pH and EC can help diagnose feeding issues or salt buildup.

SCROG (Screen of Green)

A training method using a mesh screen to spread out the canopy horizontally, increasing light exposure and maximizing yields in small grow spaces.

Stretch

The rapid growth phase that occurs in the first few weeks of flowering. Indoor growers often manage stretch with training and light placement.

T–Z: Tech, Terpenes, and Trichomes

TDS (Total Dissolved Solids)

Measured in ppm (parts per million), TDS reflects the nutrient strength in your solution. A critical value in hydro and coco grows.

Terpenes

Aromatic compounds that give cannabis its flavor and scent. Indoor growers often tailor conditions to enhance terpene production (temperature, humidity, light spectrum).

Timer

A must-have device that automates your light cycles, fan schedules, and even feeding routines. Helps keep your grow consistent and stress-free.

Training

Any technique (LST, topping, SCROG, etc.) that manipulates plant shape for better yield or structure. Indoor growers rely on training to maximize limited space.

Trichomes

Tiny, resin-filled glands that contain THC, CBD, and terpenes. The frostier your buds, the more trichomes - watch them with a jeweler’s loupe to time your harvest.

VPD (Vapor Pressure Deficit)

The difference between the moisture in the air and how much moisture the air can hold. Optimizing VPD improves plant transpiration and nutrient uptake.

Veg (Vegetative Stage)

The growth stage before flowering when the plant focuses on developing leaves and branches. Typically requires 18–24 hours of light daily.

Wattage

The amount of power your light draws. Knowing your wattage helps you calculate light intensity, coverage area, and energy costs.

Yield

The final weight of usable flower harvested. Often measured in grams per watt or grams per square foot in indoor grows.

Grow Smarter With the Right Terms

Understanding the language of indoor cultivation helps you grow more efficiently, troubleshoot faster, and get better results - without feeling like you’re guessing. Bookmark this glossary, keep it handy in your grow space, and revisit it as you level up your grow game.

Have a term you think should be added? Drop us a note - after all, growing is a community effort.

At HomeGrow Helpline, we're a homegrower-focused resource dedicated to making indoor cannabis cultivation easier, smarter, and more successful - one term and tip at a time.