Use this glossary of common hydroponic terms and get up to speed.

  • 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.

  • 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.

  • Sand or volcanic glass which has been expanded by heat; perlite holds water and nutrients on its many irregular surfaces. Mineral soil amendment.

  • The container in a hydroponic system which holds nutrient solution in reserve for use.

  • Sexual propagation: to produce seed by breeding different male and female flowers. Asexual propagation: to produce plantlets (also known as CLONES) by taking cuttings.


  • 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).

  • Calcium (Ca) and magnesium (Mg) are considered to be the secondary nutrients.

  • 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.

  • Mica which has been processed and expanded by heat. Vermiculite has excellent water-retention qualities and is a good soil amendment and medium for rooting cuttings.

  • Like copper and manganese, zinc is linked to chlorophyll synthesis.

  • The N value is the percentage of elemental nitrogen by weight in the fertilizer. The value for P is the fraction by weight of P2O5 in a fertilizer with the same amount of phosphorus that gets all of its phosphorus from P2O5. The value for K is analogous, based on a fertilizer with K2O.

  • Nitrogen is used in various forms to promote rapid vegetative growth, leaf, flower, fruit and seed development, and chlorophyll development; and to increase the protein content in all plants.

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


  • 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.

  • 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.

  • Natural insecticide made from the blossoms of various chrysanthemums.

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

  • Day length; the relationship between the length of light and dark in a 24 hour period.

  • Potassium promotes disease resistance and good development of carbohydrates, starches and sugars, and it increases fruit production. Potassium is a macronutrient.

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

  • The process of causing the initiation and development of a plant from seed.

  • The dying of plant tissue, usually the result of serious nutrient deficiency or pest attack.

  • This micronutrient is essential for nitrogen fixation and nitrate reduction.

  • 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.