Hydroponics Dictionary

Hydroponics Dictionary

GreenSea Hydroponics dictionary is packed full of many words and terms used for indoor hydroponics cultivation with a brief description clearly explaining each one and what they mean.

If you are unsure of any you have heard or read please take a look below to see if it is listed.


The PH of a solution can be tested on a scale from 0 - 14 to determine if it is acidic or alkaline. A PH reading of 7.0 is neutral and anything below this is considered to be acidic, e.g. 6.5 slightly acidic, 2.5 very acidic.


An active hydroponics growing system requires a pump or components to actively move stored water and nutrients around the system to feed your plants.


Additives or boosts can be supplied in the water with your regular nutrients and are designed to maximise your plants potential when growing, fruiting or flowering. Additives that are designed to boost plants in the fruiting or flowering period mainly contain high levels of phosphorus (P) and potassium (K).


To provide air or oxygen to soil and plant roots. Enzymes can be a very handy product for helping to aerate your soil, as they break down dead root material from your plants, fast.


True aeroponics is created with the minimal amount of contact between a plant and support. A single line of contact around the stem of the plant for support, allows 100% of the plant to be totally suspended in the air. Plants can grow above the support structure and the roots are suspended below the support structure, in the air, inside a dark chamber, and misted or sprayed permanently or regularly (timed intervals). A fine mist does not create true aeroponics, but water droplet size is important. Too large of a water droplet means less oxygen is available to the roots, and too fine of a water droplet produces excessive root hairs and develops a poor lateral root system, needed for sustained growth in aeroponic systems.


The PH of a solution can be tested on a scale from 0 - 14 to determine if it is alkaline or acidic. A PH reading of 7.0 is neutral and anything above this is considered to be alkaline, e.g. 7.5 slightly alkaline, 12.5 very alkaline.


An alternating current is an electrical current that alters the direction it travels several times a second.


Amino acids are molecules that are critical to life and are the building blocks of proteins and enzymes. Amino acids are essential to the structure and metabolism of plants.


An ampere (amp) is a unit to measure and gauge the strength of an electrical current.


A plant that completes its entire life cycle in one year or less is known as an annual.


Aphids, commonly known as greenfly, blackfly or plant lice are soft bodied insects that come in a variety of colours. They are among the most destructive pests that we encounter in our hydroponics grow rooms or outdoor gardens. Aphids suck the sugary sap from your plants and then excrete it back over the plant, producing a sticky layer on which moulds can grow. These insects live in large populations and can destroy crops with ease.



Bacteria are very small, one celled organisms that have no chlorophyll.


A ballast otherwise known as control gear consists of a transformer and capacitor and is used with high intensity discharge lighting to limit and control the flow of electricity that is provided to the lamp. Ballast's are used, as the lamp by itself would not regulate its own current consumption well enough. If a high intensity discharge lamp were connected directly to a mains power supply without a ballast unit used, it would draw an increasing amount of current very quickly and destroy itself, or the power supply.


A beneficial insect can be introduced into a grow room that has a problem with plant eating insects. Beneficial insects will kill, eat and eliminate the plant-eating insects quickly and easily.


The word Bio is from the ancient Greek language, meaning life. It is also used to describe something that is organically produced or otherwise environmentally friendly.


Products that are biodegradable are made of organic matter that can be broken down naturally, decomposing through natural bacterial action.


Blight is the imminent death of a plant. Blight is a plant that has been completely infected by diseases caused by micro-organisms and then dies.


Boron is a micronutrient that is essential to a plants membrane integrity, calcium uptake, and root elongation and to assist with the internal transport of carbohydrates. Boron affects many functions in the plant, flowering, fruiting, cell division and the movement of hormones. Boron should be available throughout the life of the plant.


Botrytis is commonly known as bud rot or grey mould, and is a form of fungus that can damage and affect many plant varieties. Wet and humid conditions in the environment and a lack of air movement are the most common cause of botrytis developing on plants that are in the process of flowering or fruiting. Fungal spores can spread quickly through flowers or fruits in these conditions and easily destroy the entire crop if plants are left untreated.



Calcium influences the water movement in cells and is necessary for cell growth and division. Calcium also activates enzymes, and some plants will require calcium to help take up nitrogen and other minerals. Calcium can easily be leached (flushed) from plants and media if required.


To calibrate, is to test and reset measuring instruments (PH, EC meters) using a solution that is fixed to a required level. Most meters are simple to calibrate with the touch of a button, and held in the required solution they will reset themselves to the desired level. Calibration of meters should be done regularly to ensure accurate readings are being taken from your nutrient solution, to avoid any problems occurring. A meter not cleaned and calibrated regularly, can obviously mislead the grower and result in optimum nutrient and PH levels not being maintained.


Sugar, starch and cellulose are all carbohydrates. It is a neutral compound of carbon, hydrogen and oxygen formed by green plants.


Carbon Dioxide (CO2) is a colourless and odourless gas that occurs naturally in our environment. Additional Co2 can be provided in grow rooms to increase photosynthesis, making your plants grow faster and larger. This requires a good quality CO2 unit to regulate and disperse the correct levels of CO2 into your grow room at the correct time, and of course a bottle of CO2. Set up and used correctly, CO2 can increase growth and yield by 30-40%.


Celsius is a scale for measuring temperature, e.g. 0 degrees Celsius, water freezes and 100 degrees Celsius, water boils.


Chelate is a process of combining nutrients, to allow plants to easily absorb and take up metal ions in the nutrients, through their roots.


Chlorine is a chemical element used to purify water. Tap water should be left for 24 hours before using, to help remove the chlorine.


Chlorophyll is a group of pigments within plant cells that absorb light energy and give a vibrant green colour to most plants. Chlorophyll is found in the chloroplasts of a cell and is necessary for plant photosynthesis.


Chlorosis is the condition of a sick plant with yellowing leaves, normally caused by a nutrient deficiency or an imbalanced PH level. Leaves produce insufficient chlorophyll, and this makes leaves turn pale, yellow and white. Plants may die from chlorosis, unless the cause of its insufficiency is treated.


A section of plant taken from a donor plant and rooted is known as a clone.


Cobalt is a micronutrient, that is a catalyst in nitrogen fixation and also essential to plant health as it is necessary for beneficial bacteria to grow and flourish. Deficient levels could result in nitrogen deficiency symptoms.


A method for checking the strength of a nutrient solution is to measure how well it conducts electricity. As nutrients are added to the water it increases the flow of electricity, so measuring the conductivity factor (CF) in a solution with a meter gives a direct indication of the strength of nutrients in a solution.


A contactor is used to control the electrical loads used to ignite and run High Intensity Discharge (HID) lights. Most contactor units will have two plugs that need connecting to a mains power supply, a box containing a relay, and sockets to plug your HID lights into. One of the contactor plugs is plugged directly into the mains power supply, and the other plug is plugged into a mechanical or digital timer and then into the mains power supply. The timer will control the on and off periods for the lights and the contactor will safely control the load that passes through to the ballast and lamp, allowing frequent on off cycles without lamp failure.


Copper is a micronutrient, which is a component of some enzymes and of vitamin A. It is required in photosynthesis, respiration and in carbohydrate and nitrogen metabolism. A copper deficiency affects plants more in the fruit and seed formation, than in vegetative growth. Copper may become toxic to plants at high levels.


A cutting is a section of plant (stem, leaves) that is removed from a donor plant at the growing tip of a branch, and placed into water or a moist growing medium for roots to develop.


Cytokinins are plant hormones that promote cell division and are primarily involved in cell growth. Cytokinins are used to help the plant make more efficient use of existing nutrients and water, and delay the ageing of leaves



Deep Water Culture is a method for hydroponics cultivation that allows the roots of your plants to be permanently submerged into water and nutrients. This would normally saturate the roots and cause the death of the plant, but by simply placing an air stone into the water and nutrient to deliver high levels of oxygen, allows the roots to flourish and your plants to survive and grow rapidly. Water and nutrients are stored in a sealed chamber or tank that can have mesh pots fitted into the top to support and grow your plants. An air pump is needed for deep water culture to work, and is fitted to air stones that are placed inside the tank, the air pump is normally run permanent to keep the water and nutrient highly oxygenated and mixed well. Deep water culture requires water levels kept high to begin, so the mesh pot is slightly submerged into the water and nutrient, keeping the young plant moist and fed. As the roots develop out of the mesh pot and into the water and nutrient, the level can be lowered slightly to suit and allow even more oxygen to the roots.


A direct current is a continuous flow of electricity that can only flow in one direction.


Drip systems deliver water and nutrients into your growing media through pipes, fittings and drippers, to feed your plants. This is a common method for hydroponics, soil and coco cultivation that is used around the world for commercial growing to produce crops indoors or outdoors. There are various designs and sizes of drippers available, but basically they all do the same job, which is to release the water and nutrients slowly into the growing media. Drip systems will normally require a water tank for storage and a pump to deliver the water through the irrigation system. When the pump is turned on, the water and nutrient will be delivered through the pipes and out of the drippers into the growing media. This type of irrigation delivery system can easily be made with pipe, fittings and drippers, and will save hours of watering large amounts of potted plants that are grown indoors or outdoors.



Ebb and Flow, also known as flood and drain is a method for hydroponics cultivation. This method stores water and nutrients in a main tank, and a pump delivers the nutrient solution into the tray or pots of the growing system to flood the media and plant roots to water and feed them. The solution is then drained from the tray or pots of the growing system, as the solution drains it pulls large amounts of air and oxygen into the media and root zone of the plants.


A method for checking the strength of a nutrient solution is to measure how well it conducts electricity. As nutrients are added to the water it increases the flow of electricity. Measuring the EC (electrical conductivity) with a meter gives a direct indication of the strength in the nutrient solution.


An embolism is a blockage in the plants vessels usually created by an air bubble, which blocks uptake of water and nutrients.


Enzymes are biological proteins that accelerate the rates of chemical reactions but do not change themselves. Enzymes are added to nutrients and additives to speed nutrient uptake through roots and also assist and speed up the process of breaking down dead root material, and enzymes also activates micro-organisms to develop new root growth fast.



Fahrenheit is a scale for measuring temperature, e.g. 32 degrees Fahrenheit water freezes and 212 degrees Fahrenheit water boils.


Flood and drain: please see Ebb and flow above for details.


Flushing is to remove unwanted nutrients and salts from plants and media, usually done towards the end of a crop cycle by applying water only for several days. Flushing can also be used for plants that have been over fed to remove excess nutrients and salts to revitalize plants.


All the leaves on a plant are considered as the foliage.


Applying a nutrient solution by mist or spray onto the leaves of a plant is to foliar feed. Foliar feeding is recommended just before your grow room lights turn off.


A fungicide is a substance that can be applied to plants to treat and eradicate any fungi present.


Mushrooms are probably the best example of a fungus, other forms of fungus are mould, rust, mildew and bacteria. They are organisms that can grow with little light as they lack chlorophyll.


Fungus gnats (black fly) are mainly black in colour and very small with long legs and thin wings. Their eggs are laid in the root zone of plants and when the larvae hatch they will eat your roots and can destroy your plants if not treated.



A seed or spore that has just sprouted and begins to grow has germinated.


Gibberellic acid is a form of gibberellins and is a plant growth hormone used to promote stem elongation.


GreenSea Hydroponics, a great place to shop for all your hydroponic needs.



High Intensity Discharge lights are used for indoor plant cultivation and are very powerful. They produce many lumens (light output) essential for photosynthesis.


High-pressure sodium (HPS) lamps are used for HID lighting to flower plants. Electricity is passed through a sodium vapour inside bulb to emit a yellow/red light source.


Horticulture is a science and art of cultivating plants.


Humidity is the ratio between the amount of moisture in the air and the greatest amount of moisture the air could hold at the same temperature.


Hydroponics is an art of cultivating plants in a nutrient rich solution, without any soil.


A hygrometer is an instrument used to measure relative humidity (RH) in the atmosphere.



Inert is a term used in hydroponics to describe a growing substrate/media that is not chemically active and has no nutritional content.


Insecticide is any material or solution that will inhibit or kill insects.


Iron is a micronutrient and is essential for chlorophyll production, which is why a deficiency results in chlorosis. Iron permits the plant to use the energy provided by sugar.



A small compressed peat pellet, encased in a biodegradable mesh. Jiffy plugs when soaked will swell and allow for seeds or cuttings to be propagated and grown.



Kelp is a type of seaweed that can be used as a plant fertiliser. Seaweed extract is commonly sold for hydroponics cultivation and contains the primary nutrients (NPK), trace elements and amino acids.



Leaching also called flushing is to remove unwanted nutrients and salts from plants and media, usually done towards the end of a crop cycle by applying water only for several days. Leaching can also be used for plants that have been over fed to remove excess nutrients and salts to revitalise plants.


Light rails can be mounted on ceilings or suspended in grow rooms to hang lights. Moving lights slowly, backwards and forwards across plants they allow less lighting to be used and also lights can be positioned closer to plant canopy as it is not stationary and producing a hot spot on plants.


Lumen is the measurement of light intensity. One lumen is equal to the amount of light emitted by one candle that falls on one square foot of surface that is one foot away from the candle.



There are 6 macronutrients. Nitrogen (N), phosphorus (P) and potassium (K) are the primary macronutrients and are needed in large quantities. Calcium (Ca), magnesium (Mg) and sulphur (S) are the secondary macronutrients and are needed in smaller quantities.


Manganese is a micronutrient that activates important enzymes involved in chlorophyll formation. Manganese assists in nitrogen utilization along with iron in chlorophyll production.


Media is a term used for a material that is used for growing plants in. Hydroponics requires an inert (chemically inactive) media to be used such as rockwool or clay pebbles. Soil, coco coir, perlite, vermiculite are all types of media that can be used.


Metal halide lamps are high-pressure discharge lamps that produce high levels of white light (daylight), and are used for the vegetative (growing) period of a plants life.


Micronutrients also called trace elements are essential to plant health and must be present in your nutrient solution in very small amounts. Copper (Cu), zinc (Zn), iron (Fe), manganese (Mn), boron (B), molybdenum (Mb), chlorine (Cl) and cobalt (Co) are micronutrients needed for plants.


Minerals are elements or chemical compounds that are normally crystalline and that have been formed as a result of geological processes over many years. Phosphorus, potassium, sodium and chlorine are examples of minerals.


Molasses is a by-product that is very thick and is produced from the processing of sugar cane and sugar beet into sugar.


Molybdenum is a micronutrient that is used by plants to reduce nitrates into usable forms and is essential to plant health. Molybdenum is most active in roots and seeds



PH is read on a scale of 0-14, with 7.0 being neutral.


Nitrogen is a macronutrient and is used in large quantities during the growing period of plants, essential for fast growth.


Nitrogen (N), Phosphorus (P) and Potassium (K) are the three primary nutrients needed in large amounts for successful plant growth and flowering.


Nutrients are essential elements for plants to live. Carbon, hydrogen and oxygen are absorbed from the air and water. The rest of the elements, called nutrients are absorbed through plant roots from the growing media and nutrient solution supplied.


NFT is a method for hydroponics that works extremely well. When young plants are rooted and established well they can be transplanted to gullies or trays. Capillary matting is usually placed inside gullies or trays to allow an even distribution of water and nutrients. A pump will deliver a thin film of solution into gullies or trays encouraging roots to grow and spread into capillary matting and then excess solution will then drain and return to the main tank and re-circulate.



Organic material is made from or derived from living organisms. Organic stands for natural in agriculture, and organic stands for a molecule or substance that contains carbon in chemistry.


Osmosis is the movement of fluids through a semi permeable membrane, such as in a living cell.



A parasite is an organism that lives on or inside another host, without benefiting the host. Fungus is a parasite.


Parts per million is a scale used to measure the strength of nutrient in a solution.


A hydroponic system that delivers water and nutrients to plant roots through absorption or capillary action is passive. Hand feeding plants with water and nutrients into trays or pot saucers and allowing plants and medium to absorb solution is passive feeding.


A pathogen is a micro-organism (germ) that causes diseases and is harmful to plants, usually bad bacteria, fungi and viruses. Growing media can be a common place for harbouring pathogens.


A plant that completes its life cycle over several years is perennial.


Perlite is a growing media that is made from volcanic rock, heated to extreme temperatures to produce very small lightweight glass pebbles. Perlite can be used alone or mixed with soil to aerate the media, and perlite also holds water and nutrients well.


Phosphorus is a macronutrient that is used by plants to aid metabolism and transfer energy and phosphorus also plays a major role in flower formation.


The photoperiod is the hours of light received by plants, compared to the hours of darkness received by plants in a 24 hour cycle. The photoperiod affects the growth and maturity of plants.


Photosynthesis is the building of chemical compounds when plants absorb energy from light, water and Co2.


Potassium is a macronutrient that is used in larger amounts when flowering plants to help sugar production, essential for the development of large vibrant flowers.


A solution can be acidic or alkaline. PH (potential hydrogen) is used as an indicator of how acidic or alkaline a solution is. The PH scale ranges from 0-14, a solution with a PH value of 7 is neutral, below 7 to 0 is acidic with 0 being very acidic and above 7 to 14 is alkaline with 14 being very alkaline. Maintaining the correct PH level is critical for soil and hydroponically grown plants, as they will easily absorb all nutrients with the correct PH level maintained for the type of plant grown.


The primary nutrients essential for plant growth are nitrogen (N), phosphorus (P) and potassium (K).


Pythium is a fungal disease that affects plant roots. Root rot is a common crop disease caused by a group of organisms called Pythium.



Hydroponics systems that are designed to store water and nutrients in a main tank for delivery to plants and then allow excess water and nutrient to return to main tank through the system or pipes are re-circulating hydroponics systems.


Reverse osmosis is a technique for purifying water through filters and membranes.


Rockwool is an inert growing media used for hydroponics that is made from mineral wool.


Hydroponics systems that are designed to store water and nutrients in a main tank for delivery to plants and then drain excess water and nutrients through pipes to a waste tank or outdoor drains are run to waste hydroponics systems.



Sea of green is a technique of cultivating a large number of plants in a small area. Sea of green allows plants to be positioned closer in hydroponics systems and for less lighting to be used. Plants can be fruited or flowered straight away and still produce a good yield as there are many more plants grown.


Spectrum is the band of colours that can be emitted by a light source. Most commonly used for hydroponics are blue spectrum lights for growing plants, and red spectrum lights for flowering plants. There are many other coloured lights available with a different colour spectrum produced.


Probably your worst enemy indoors are spider mites, which mainly live on the underside of leaves in hot and dry conditions. Adult mites are about 1mm in size and will lay eggs on the leaves and then spin silk webs for protection from predators. Spider mites will puncture plant cells and suck away all the goodness from your plants, normally leaving yellow or white spots on leaves. If left they can multiply fast and cause havoc and eliminate your crop with ease.


To clean and remove all germs and bacteria is to sterilize.



A thermometer is used to measure and record the temperature of your grow room in Celsius or Fahrenheit.


A thermostat is a unit used to regulate the temperature in an enclosed environment. A thermostat can be fitted to either a fan or heater to raise or lower the temperature automatically.


Tip burn is normally associated with too much nutrient applied to the growing media and fed to plants. This causes the tips of leaves to turn brown, dry and fall off.


TDS stands for total dissolved solids and is a measure of all organic and inorganic substances contained in a liquid. Some hydroponic nutrient meters give readings displayed in TDS, to give you an accurate measure of the strength of nutrient in the water.


A transformer is used inside the ballast for HID lights, to alter electrical power from one voltage to another.


To uproot and remove a plant and root ball and then re-plant into larger pots with new soil or systems is to transplant.



Ultra violet light has very short wavelengths, just beyond the visible spectrum of violet light.



Ventilation is essential indoors for plants to survive. The removal of hot stale air and supply of clean fresh air can be achieved with fans and ducting to ventilate your grow room.


Vertical growing allows many plants to be supported vertically in a system and surrounding the lights. This method allows many more plants to be grown with less lighting used and also less floor space used.



A wetting agent is a compound used when foliar feeding plants. A wetting agent will help to reduce droplet size when spraying or misting plants and cover the plants surface area more easily with your solution.


A wick can be used for passive hydroponics. The wick is suspended into the nutrient solution to allow water and nutrients to be absorbed up the wick and into the media and plant roots.


Wilt is when a plant becomes limp and leaves droop from lack of water.



Xylem is the vascular woody tissue that helps transport water and dissolved minerals from the roots and up throughout the stems and leaves.



Yellow syndrome is also a term for Chlorosis. Chlorosis is the condition of a sick plant with yellowing leaves, normally caused by a nutrient deficiency or an imbalanced PH level. Leaves produce insufficient chlorophyll, and this makes leaves turn pale, yellow and white. Plants may die from chlorosis, unless the cause of its insufficiency is treated.



Zinc is a micronutrient that activates many enzymes and participates in chlorophyll formation. Zinc is an essential catalyst for most plants enzymes and auxins, and it is crucial for stem growth. Zinc plays a vital part in sugar and protein production.


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