Abscission: The shedding or dropping of fruits, flowers or leaves.
Aeration: The process of providing oxygen to plant roots to encourage nutrient uptake, root development and overall health.
Aeroponics: A growing technique in which plants are maintained without the aid of a grow medium. Done by exposing the bare roots to an atomized nutrient spray on a regular schedule. Aeroponic plants are typically suspended on a platform and supported by a collar, which makes it look like they’re growing on air.
Air Stone: An air pump accessory used to oxygenate liquid nutrients.
Aquaponics: A mutually beneficial growing arrangement where fish and plants are cultivated together.
Ballast: A mechanism in a light assembly that contains the controls and electronics.
Bloom Booster: A special fertilizer that contains high concentrations of phosphorus and other minerals that increase flowering.
Boron (B): A micronutrient that helps regulate other nutrients.
Calcium (Ca): A secondary macronutrient that aids in the development of strong plant stems and roots.
Candela: A unit used to measure light intensity.
Candle Power (CP): Light intensity based on the luminosity generated by an average candle, and measured more accurately in candela units.
Carbon Dioxide (CO2): A naturally occurring gas used by plants during photosynthesis.
Chlorine (Cl): A micronutrient essential for photosynthesis.
Chlorosis: A nutrient deficiency characterized by yellow or brown leaves that occurs when there is a drop in chlorophyll production. The most likely cause is a mineral deficiency or pH imbalance.
Clay Pebbles: A porous, clay-based medium used to grow plants without soil. Clay pebbles anchor plant roots, help retain moisture and enhance aeration. Created using high heat, clay pebbles are highly textured, have a neutral pH and are typically reusable.
Cloning: The asexual reproduction of a plant that results in a duplicate of the original.
Coco Coir: A popular, inert grow medium made from shredded coconut husks. Coco coir is considered flexible and easy to use.
Compact Fluorescent: A variety of fluorescent lightbulb in which the controls are attached to the bulb, not contained in the fixture.
Copper (Cu): A micronutrient that helps promote growth and flowering.
Deep Water Culture (DWC): A simple hydroponic system in which plant roots are totally submerged in a nutrient mixture and aerated using an air pump. DWC is the most suitable system for growing lettuces and other water-loving plants.
Drip: A nutrient and water delivery system that works somewhat the way watering works in a soil-based garden. Although there are a number of ways to design a drip system, in many of the most popular, nutrients are delivered to the media (often slow-draining stonewool or coco coir) through a series of large distribution tubes and small, perforated feeder tubes. The excess drains into a reservoir and is recycled using an electric water pump, manual pulley system or other means. This is sometimes referred to as a gravity-fed system, particularly when no electric pump is used.
Ebb and Flow: A simple and reliable hydroponic system that uses timed irrigation to provide nutrients to plant roots. It does this by saturating the grow media and allowing the liquid nutrient to drain completely between applications. Flooding and draining also evacuates and replenishes stale air around plant roots for enhanced aeration.
Electrical Conductivity (EC): The measurement of water’s ability to conduct an electrical charge. Even a small amount of ions in a water solution make it capable of conducting electricity. The higher the solution’s salt concentration, the better it conducts electricity.
Fertilizer Burn: A symptom of over-fertilization in which leaf tips and margins turn yellow and distort.
Flood & Drain: See Ebb and Flow.
Fluorescent: An economical, artificial light source for plants. Fluorescent lights run cool and have a good spread, but provide a limited spectrum that may not be suitable for all applications. Fluorescent lighting is widely considered most effective for growing seedlings and leafy greens.
Fogponics: A form of aeroponics that uses a fine mist spray to produce nutrient vapor. This method of nutrient delivery may enhance absorption and reduce costs by using resources like nutrients, water and energy more efficiently.
Foliar Feeding: A method of providing nutrition to plants through their leaves.
Gravity Fed: See Drip.
Grow Light or Lamp: Lighting designed to enhance plant growth by mimicking sunlight or the specific light wavelengths preferred by plants during different times in their development (primarily blue or red light).
Grow Tent: A soft-sided enclosure for plants supported by a sturdy internal frame.
Grow Tray: An open receptacle used to house plants.
High Intensity Discharge (HID): Highly efficient and long-lasting lighting technology that uses an integrated transformer, capacitor and lamp assembly. Available in metal halide (blue light) and high pressure sodium (red or orange light). Because they run hot, HID lamps are often used in open or large spaces or with enhanced ventilation.
High Pressure Sodium (HPS): A type of HID light that uses the red/orange end of the light spectrum. It is preferred for the flowering and fruiting phases of many plants.
Iron (Fe): A micronutrient important for photosynthesis and many other plant functions.
Light-emitting Diodes (LEDs): A versatile, low-energy, durable lighting option able to target different portions of the light spectrum. Believed to work best when paired with highly reflective materials like Mylar.
Lumen (lm): A measurement of the visible illumination emitted by a light source.
Macronutrients: A group of primary nutrients required by plants. Often referred to as the big three, they are nitrogen, phosphorous and potassium (N-P-K).
Manganese (Mn): A micronutrient important for photosynthesis and the activation of enzymes that trigger different phases in a plant’s life cycle.
Medium or Media: An inert anchoring material that supports plants in a hydroponic system. Also known as a substrate, these materials can enhance aeration, aid in nutrient distribution and help sustain beneficial bacteria.
Metal Halide (MH): A type of HID light that favors the blue end of the light spectrum. Preferred for the vegetative growth phase of many plants.
Micronutrients: A group of trace elements that work with macronutrients to sustain plants. Although dozens of minerals may be of use to plants in nature, hydroponic nutrient blends use the most beneficial. Manufacturers add micronutrients to their products using proprietary recipes. Trace elements include boron, chlorine, copper, iron, manganese, molybdenum and zinc.
Mistponics: See Fogponics.
Molybdenum (Mo): A micronutrient used in plant cultivation that aids in nitrogen fixing.
Nanometer (nm): A metric unit used to measure light wavelengths. A nanometer is equal to one billionth (.000000001) of a meter.
Nitrogen (N): One of the macronutrients, nitrogen is a colorless, odorless gas used in a number of forms to promote plant development.
Nutrient Film Technique (NFT): A method of hydroponic cultivation that uses sloping trays or tubes, a recirculating pump and sometimes a wicking system to deliver a thin-but-continuous stream of nutrients to plant roots. Good air flow is also built into the system. This type of scalable hydroponic set-up is popular for both small and large applications.
Nutrient Solution: A mixture of macronutrients, micronutrients and water used to nourish plants in a soilless growing system.
Peat Moss: A relatively inert, organic grow medium. Retains a lot of moisture while allowing for plenty of oxygen to be present in the root zone. Falls apart easily and needs to be replaced periodically.
Perlite: An inert growing medium for hydroponic cultivation made from heat-expanded volcanic glass or sand. Perlite is often used in combination with other media to provide better aeration.
pH: pH is a scale representing acidity and alkalinity as a numbered range from 1-14. The low end of the scale represents acidic values (1-6), with 1 being the most acidic. The high end of the scale represents alkaline values (8-14), with 14 being the most alkaline. Seven is neutral (neither acidic nor alkaline).
Phosphorus (P): A macronutrient essential for plant growth. Promotes leaf and root development, blooming and seed production.
Photoperiod: Light duration in plant cultivation. This is also expressed as day length.
Photosynthesis: A plant process that uses carbon dioxide and water to turn sunlight into usable energy in the form of carbohydrates (sugar).
Plasma: One of the newest lighting technologies on the market. Offers a broad spectrum of light with a lower heat output and possibly lower energy costs.
Potassium (K): A macronutrient essential to plant growth. Promotes fruit production and enhances resistance to disease.
PPM: See Total Dissolved Solids.
Reflector: The reflective hood of a light fixture designed to maximize light distribution and reduce hot spots.
Reservoir: A receptacle that holds nutrients within a hydroponic system.
Run to Waste: A basic hydroponic system that does not recycle unused nutrients.
Secondary Macronutrients: The dissolved nutrients used to maintain plants hydroponically are broken into three categories: macronutrients, secondary macronutrients and micronutrients. Secondary macronutrients are considered vital but less essential that the big three: nitrogen, phosphorous and potassium. Secondary macronutrients include calcium magnesium and sulfur.
Stonewool: Stonewool, also known as rockwool, is one of the most popular grow mediums. It is made by heating and spinning certain silica-based rock (basalt) into a material much like cotton candy. The end product is a firm, fibrous material that provides an ideal ratio of water to oxygen for optimal conditions for plant roots.
Substrate: See Medium or Media.
Total Dissolved Solids: Dissolved mineral nutrients present in water as measured in parts per million (ppm).
Vermiculite: Processed mica used as an inert, hydroponic grow medium.
Wick (or Wicking): A simple hydroponic technique in which nutrient solution is delivered to plant roots through a capillary action using a wick.
Zinc (Zn): A micronutrient that aids plants in the production of chlorophyll.
While there isn’t space here to share all of the ingenious and useful words associated with hydroponics, we’ve aimed to include the most important.