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Acid: refers to medium or nutrient solution with a low pH; an acidic solution has a pH below 7.

Adobe: a dark, heavy soil, containing clay; not suitable for container gardening or hydroponics.

Aeration: supplying soil and roots with air or oxygen. In some hydroponic systems, a nutrient solution is aerated by the output of an aquarium pump.

Aerponics: a system in which the roots of a plant are consistently or intermittently misted with fine droplets of nutrient solution.

Aggregate:- medium usually grow rocks, gavel, or lava rocks that is all nearly the same size, and used for an inert hydroponic medium.

Alkaline: refers to medium or nutrient solution with a high pH; any pH over 7 is considered alkaline.

All-purpose (General-purpose) fertilizer: - a balanced blend of N-P-K; all purpose fertilizer for soil and is used by most growers in the vegetative growth stage. Miracle-Gro and Peters is an example. They are not recommended for hydroponics.

Alternating Current(AC): an electric current that reverses its direction at regular occurring intervals. homes have AC.

Amendment: fortifying soil by adding organic or mineral substances in order to improve texture, nutrient content or biological activity.

Annual: a plant that normally completes it's entire life cycle in one year or less. Tomatoes are an example of an annual plant.

Auxin: classification of plant hormones; auxins are responsible for foliage and root elongation.


Bacteria: very small, one-celled organisms.

Beneficial Insect: a good insect that eats bad flower and vegetable munching insects.

Biodegradeable: able to decompose or break down through natural bacterial or fungal action, substances made of organic matter are biodegradable.

Bleach: ordinary laundry bleach is used in a 1 part bleach to 10 parts water solution as a garden fungicide. Use this solution to clean all your equipment between harvests to rid of any lingering contamination.

Bloom Booster, Blossom Booster: fertilizer high in phosphorus (P) that increases flower yield.

Bolt: term used to describe a plant that has gone to seed prematurely.

Bonsai: a very short or dwarfed plant.

Boron: the function of this micronutrient is not well understood, but it is suspected that it might aid carbohydrate transport.

Breath: roots draw in and breath oxygen, stomata draw in and breathe CO2

Bud Blight: a withering condition that attacks flower buds.

Buffering: the ability of a substance to reduce shock and cushion against pH fluctuations.

Burn: leaf tips that turn dark from excess fertilizer and salt burn.


Calcium (Ca): calcium is vital in all parts of plants to promote the translocation of carbohydrates, healthy cell wall structure, strong stems, membrane maintenance and root structure development. Calcium is a macronutrient.

Calyx: the pod harboring female ovule and two protruding pistils, seed pod.

Carbohydrate: neutral compound of carbon, hydrogen and oxygen; Sugar, starch and cellulose are carbohydrates.

Carbon Dioxide (CO2): a colorless, odorless, tasteless gas in the air necessary for plant life. Occurs naturally in the atmosphere at .03%.

Caustic: capable of destroying, killing or eating away by chemical activity.

Cell: the base structural unit that plants are made of: Cells contain a nucleus, membrane, and chloroplasts.
Cellulose: a complex carbohydrate that stiffens a plants tissue.

CFM: cubic feet per minute.

Chelate: combining nutrients in an atomic ring that is easy for plants to absorb.

Chlorine (Cl): this micronutrient is essential for photosynthesis, where it acts as an enzyme activator during the production of oxygen from water.

Chloroplast: containing chlorophyll.

Chlorosis: the condition of a sick plant with yellowing leaves due to inadequate formation of chlorophyll. Chlorosis is caused by a nutrient deficiency, usually iron or nitrogen; nutrient deficiencies are themselves often caused by a pH that is out of the acceptable range.

Chlorphyll: the green photosynthetic matter of plants: Chlorophyll is found in the chloroplasts of a cell.

Clay: soil made of very tine organic and mineral particles: Clay is not suitable for container gardening.

Climate: the average condition of the weather in a garden room or outdoors.

Clone: a plant produced through asexual reproduction including, but not limited to, cuttings, layering and tissue culture.

Color Tracer: a coloring agent added to many commercial fertilizers, notifies the horticulturist of fertilizer in the solution.

Compaction: soil condition that results from tightly packing soil; compacted soil allows for only marginal aeration and root penetration.

Companion Planting: planting garlic, marigolds, etc., along with other plants to discourage insect infestation.

Compost: a mixture of decayed organic matter.

Conditioning: to soak new Rockwool in an acidic solution to lower the pH from 8.0 to 5.5.

Copper (Cu): this micronutrient is an internal catalyst and acts as an electron carrier; it is also believed to play a role in nitrogen fixation.

Cotyledon: energy storage components of a seed that feed the plant before the emergence of its first true leaves.

Cross-pollinate: pollinating two plants having different ancestry.

Cubic Foot: volume measurement in feet: L” x W” x H” ÷ 1728” = CU. FT. Cutting: (1) Growing tip cut from a parent plant for asexual propagation (2) Clone.

Cutting: 1. growing tip cut from a parent plant for asexual propagation 2. clone


Damping-Off: disease that attacks young seedlings and cuttings, causing stem to rot at base; overwatering is the main cause of damping-off.

Deplete: exhaust soil of nutrients, making in infertile: Once a soil is used it is depleted
Desiccate: cause to dry up.

Dioecious: having distinct male and female flowers.

Dissolved Solids or Total Disolved Solids: the amount of dissolved solids, usually fertilizer salts, that are measured in water in parts per million.

Drainage: way to empty soil of excess water: With good drainage, water passes through soil evenly.

Drip Aeration: a hydroponic method wherein air pressure from a small air pump is used to percolate nutrient solution out through a ring of feeder tubing which encircles the plant.

Drip Line: a line around a plant directly under its outermost branch tips; Roots seldom grow beyond the drip line.

Drip System (Drip Emitter System): a very efficient watering system that employs a main hose with small water emitters. Water is metered out of the emitters, one drop at a time.

Dry Ice: a cold, white substance formed when carbon dioxide is compressed and cooled; dry ice changes into CO2 gas at room temperature.

Dry Well: drain hole, filled with rocks


Ebb-and-Flow (or Flood and drain): a hydroponic system in which the medium, usually aggregate pebbles, is periodically flooded with nutrient solution and then drained again, feeding and aerating the medium and root system.

Elongate: grow in length.


Feed (F): deliver nutrient to the plant via roots or foliage.

Female: pistillate, ovule, seed-producing.

Fertigate: to fertilize and irrigate at the same time.

Fertlizer Burn: over fertilization: first leaf tips burn (turn brown) then the leaves curl.

Flat: shallow (3”) deep container, often 18x24 or 10x20 inches with good drainage, used to start seedlings or cuttings.

Foliage: the leaves or more generally, the green part of a plant.

Foliar Feeding: misting plants with fertilizer solution, which is absorbed by the foliage.

Fungicide: a product that destroys or inhibits fungus.

Fungistat: a product that inhibits fungus keeping it in check.

Fungus: any of a major group (Fungi) of saprophytic and parasitic spore-producing organisms usually classified as plants that lack chlorophyll and include molds, rusts, mildews, smuts, mushrooms, and yeasts. Common fungal diseases that attack plants are "damping-off," Botrytis, and powdery mildew.


Gene: part of a chromosome that influences the development of plant; genes are inherited through sexual propagation.

Genetic Make up: the set of genes inherited from parent plants.

Geolite: one of several brand names/varieties of clay aggregate medium (also known as LECA for light expanded clay aggregate). It is a lightweight, porous substrate with excellent aeration. Because it does not really wick water effectively, Geolite and other LECA mediums are favorites in ebb-and-flow and drip hydroponic systems.

Germination: the process of causing the initiation and development of a plant from seed.

GPM (G): gallons per minute.

Gypsum: a mineral soil amendment, which adds Calcium and Sulfur to the soil without affecting the soil's pH.


Harden-off: to gradually acclimatize a plant to a more harsh environment. A seedling must be hardened-off before planting outdoors.

Hermaphrodite: one plant having both male and female flowers: The breeding of hermaphrodites is hard to control.
Hertz (HZ): a unit of frequency that cycles one time each second: A home with 60 hertz AC current cycles 60 times per second.

Honey Dew: a sticky, honey like substance secreted into foliage by aphids, scale and mealy bugs.

Horizontal: parallel to the horizon, ground or floor.

Hormone: chemical substance that controls the growth and development of a plant. Root-inducing hormones help cuttings root.

Hose Bib: water outlet containing an on/off valve,

Humidity: (Relative): ratio between the amount of moisture in the air and the greatest amount of moisture the air could hold at the same temperature.

Humus: dark, fertile, partially decomposed plant or animal matter; humus forms the organic portion of the soil.

Hybrid: the offspring from two plants of different breeds, variety or genetic make-up.

Hydrated Lime: instantly soluble lime, used to raise or lower pH.

Hydrogen: light, colorless, odorless gas: Hydrogen combines with oxygen to form water.

Hygrometer: an instrument for measuring relative humidity in the atmosphere.


Inbred: (True Breed) offspring of plants of the same breed or ancestry.

Inert: chemically non-reactive; inert growing mediums make it easy to control the chemistry of the nutrient solution.

Insecticial Soap: an organic mixture that is effective in destroying soft-bodied insects such as: aphids, mealy bugs, spider mites, and thrips. It breaks down the coating that helps insects retain moisture causing dehydration and death.

Iron (Fe): this micronutrient acts as a catalyst in the photosynthesis/respiration process, and is essential for the formation of sugars and starches. Iron also activates certain other enzymes.


 Leach: solve or wash out soluble components of soil by heavy watering.

Leaf Curl: leaf malformation due to overwatering, over fertilization, lack of magnesium, insect or fungus damage or negative tropism.

Leaflet: small immature leaf.

Leaves: the external part of a plant attached to branches and stems for the purpose of taking in light from the sun’s energy. They do this with chloroplasts in the cells which contain chlorophyll.

Leggy: abnormally tall internode space, with sparse foliage. Leggyness of a plant is usually caused by lack of blue light or CO2. Too much nitrogen can also cause this.

Life Cycle: a series of growth stages through which a plant must pass in its natural lifetime; the stages for an annual plant are seed, seedling, vegetative and floral.

Lime: used in the form of dolomite or hydrated lime to raise and stabilize soil pH.

Litmus Paper: chemically sensitive paper used for testing pH.

Loam: organic soil mixture of crumbly clay, silt and sand.


Macro-nutrients: the primary nutrients N-P-K or the secondary nutrients magnesium and calcium.

Magnesium: a secondary macronutrient essential for plant growth. Helps activate enzymes that form oils, starch, and fats, magnesium also is a component of the chlorophyll molecule.

Manganese (Mn): this micronutrient activates one or more enzymes in fatty acid synthesis; it also activates the enzymes responsible for DNA and RNA production. Closely associated with copper and zinc, manganese also participates directly in the photosynthetic creation of oxygen from water.

Medium: the substrate or soilless material which supports the plant and absorbs and releases the nutrient solution in hydroponic horticulture.

Meristem: lip of plant growth, branch lip.

Micronutrients: also referred to a TRACE ELEMENTS, including sulfur (S), Iron (Fe), Manganese (Mn), Boron (B), Molybdenum (Mo), Zinc (Zn), and Copper (Cu).

Millimeter: thousandth of a meter; approximately .04 inch.

Moisture Meter: an electronic device that measures the exact moisture content of soil at any given point.

Molybdenum (Mo): this micronutrient is essential for nitrogen fixation and nitrate reduction.

Mulch: a protective covering of organic compost, leaves, etc. Indoors, mulch keeps soil too moist and possible fungus could result.

Mycorrhizae: mutualistic association of a fungus with the root of higher plant. In this relationship, the fungus helps the plant in extracting certain nutrients from the soil. In exchange, the fungus is provided with a habitat and nutrition in the form of carbohydrates.


Necrosis: the dying of plant tissue, usually the result of serious nutrient deficiency or pest attack.

Neem Oil: an extract derived from the neem tree and contains a wide variety of compounds. The collective action is that of insect repellent, feeding inhibitor, egg-laying deterrent, growth retardant, sterilant and toxin. It affects some 170 insect species and is relatively non-toxic to mammals.

Nitrogen (N): one of the three macronutrients essential for plant growth. Nitrogen is a major component of plants; it is a building block of amino acids, proteins, and nucleic acids (genetic material), chlorophyll, and enzymes.

N-P-K: an abbreviation for nitrogen (N), phosphorus (P), and potassium (K). In the chemical philosophy, these three elements are considered important to force crop production

NFT (Nutrient Film Technique): a hydroponic method in which nutrient is fed into grow tubes or trays in a thin film where the roots draw it up. This "nutrient film" allows the roots to have constant contact with the nutrient and the air layer above at the same time.

Nutrients: the elements needed by plants for normal growth and health. The major nutrients (Macronutrients) are nitrogen (N), phosphorus (P), and potassium (K), but there are numerous Micronutrients (also called Trace Elements) which also have integral roles in maintaining plant health. A good quality hydroponic nutrient formula will contain all of the major nutrients and micronutrients needed by the vast majority of plants.

Nutrient Solution: the mixture of water and water-soluble nutrients which is provided to the plants for nourishment in a hydroponic system.


Organic: made of, or derived from or related to living organisms. In agriculture organic means “natural”. In chemistry organic means “a molecule or substance that contains carbon”.

Outbred: see 'Hybrid'

Ovule: a plant’s egg found within the calyx, it contains all the female genes; when fertilized, an ovule will grow into a seed.

Oxygen: tasteless, colorless element, necessary in soil to sustain plant life.


Parasite: organism that lives on or in another host organism; fungus is a parasite.

Peat: partially decomposed vegetation (usually moss) with slow decay due to extreme moisture and cold.

Perennial: a plant, such as a tree or shrub, that completes its life cycle over several years,

Perlite: (1) sand or volcanic glass which has been expanded by heat to 1,600 F; useful in opening cavaties to allow water and air to reach the roots. (2) mineral soil amendment.

pH: a scale from 1 to 14 that measures the acid to alkaline balance of a growing medium (or any other substance). In general, plants grow best in a pH range of 6 to 6.8; 6.3 is considered ideal. If the pH is not within the acceptable range, nutrients may not be absorbed to maximum capacity.

pH Tester: electronic instrument or chemical used to find where soil or water is on the pH scale.

Phosphorus (P): phosphorus promotes and stimulates early growth and blooming and root growth. It hastens maturity and seed growth, and contributes to the general hardiness of plants. Phosphorus is a macronutrient.

Photoperiod: day length; the relationship between the length of light and dark in a 24 hour period.

Photosynthesis: the process by which plants use light energy to collect carbon dioxide from the atmosphere and convert it to chemical energy in the form of sugar.

Pod Seed: a dry calyx containing a mature or maturing seed.

Pollen: fine, dust like micro-spores containing male genes.

Potassium (K): potassium promotes disease resistance and good development of carbohydrates, starches and sugars, and it increases fruit production. Potassium is a macronutrient.


     Sexual propagation: to produce seed by breeding different male and female flowers.

     Asexual propagation: to produce plantlets (also known as CLONES) by taking cuttings.

Prune: alter the shape and growth pattern of a plant by cutting stems and shoots.

Pyrethrum: natural insecticide made from the blossoms of various chrysanthemums.


Rejuvenate: restore youth: A mature plant, having completed its life cycle (flowering), may be stimulated by a new 18 hour photoperiod, to rejuvenate or produce new vegetative growth.
Reservoir: the container in a hydroponic system which holds nutrient solution in reserve for use.

Rockwool: inert, soilless growing medium consisting of woven, thin strand-like fibers made from molten volcanic rock and limestone, which is heated to over 2900 degrees F, extruded, and formed into slabs, cubes and blocks.

Root Bound: roots stifled or inhibited from normal growth, by the confines of a container.

Roots: their purpose is to anchor a plant and provide a means in which to feed and hydrate a plant.


Salt: crystalline compound that results from improper pH or toxic buildup of fertilizer. Salt will burn plants, preventing them from absorbing nutrients.

Secondary Nutrients: calcium (Ca) and magnesium (Mg) are considered to be the secondary nutrients.

Seed Pod: a dry calyx containing a mature or maturing seed.

Soluble: able to be dissolved in water

Spore: seed-like offspring of a fungus.

Sprout: (1) a recently germinated seed (2) Small new growth of a leaf or stem.

Square feet (sq. ft.) - length (in feet) times width equals square feet.
Stamen: male, pollen-producing.

Starch: complex carbohydrate; starch is manufactured and stored in food.

Sterilize: make sterile (super-clean) by removing dirt, germs and bacteria. A good sterilizer for hydroponic equipment is a 10 percent bleach to water solution.

Stress: a physical or chemical factor that causes extra exertion by plants: A stressed plant will not grow as well as a non-stressed plant.

Stomata: small mouth like or nose like openings (pores) on leaf underside, responsible for transpiration and many other life functions; the millions of stomata, must be kept very clean to function properly.

Sugar: food product of plant. Carbohydrates that contain hydrocarbon chain.

Synthesis: production of a substance, such as chlorophyll, by uniting light energy and elements or chemical compounds.

Systemic: used in reference to a disease within the plant tissue, not initiated from the external cells. Also refers to materials and compounds which are taken up or absorbed by the plant and designed to fight disease (e.g. systemic fungicide).


Tap Root: the main or primary root that grows from the seed; lateral roots will branch off the tap root.

Tepid: warm 70 to 80 degrees F (21 to 27 degrees C); always use tepid water around plants to facilitate chemical processes and ease shock.

Terminal Bud: bud at the growing end of the main stem.

Tonic Life: the amount of time a pesticide or fungicide remains active or live.

Transpire: give off water vapor and by products via stomata and carbon dioxide intake at the leaves.


Urea: a water-soluble powder created by the chemical reaction of liquid ammonia and liquid carbon dioxide.


Vegetative: not flowering. the stage of development when a plant is producing only roots, stems and leaves, that is, the vegetative organs.

Vent: an opening, such as a window, serving as an outlet for air. 

Vertical: upright; perpendicular to the plane of the horizon. 

Ventilation: circulation of fresh air in place of air that has been used or contaminated, fundamental to a healthy indoor garden, an exhaust fan is an affordable option. 

Vermiculite: is a light, mica-derived mineral expanded by heat; added to potting mix will improve aeration and moisture retention qualities; is good for soil amendment and medium for rooting cuttings.

Wetting Agent: compound that reduces the droplet size and lowers the surface tension of the water, making it moist.


Wick: part of a passive hydroponic system using a wick suspended in nutrient solution. The nutrients pass up the wick and are absorbed by the medium and roots.

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