Plant & Garden Glossary


Supplying soil and roots with air or oxygen. Geolite is an example of a medium with excellent aeration. In some hydroponic systems, a nutrient solution is aerated by the output of an aquarium pump.


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


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


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

Asexual Propagation

To produce plantlets (also known as CLONES) by taking cuttings.

Bloom Booster

Fertilizer high in phosphorus (P) that increases flower yield.


Leaf edges that turn a brownish / yellow color and look dead from excess fertilizer and salt burn.

Carbon Dioxide (CO2)

A colorless, odorless, tasteless gas in the air necessary for plant life. Occurs naturally in the atmosphere at .03%.


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.


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

Coco Coir

An organic growing medium made from the husk of coconuts designed for improved aeration and drainage capabilities.  Coco Coir has become very popular because its an earth friendly renewable resource and gives great growth results.


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

Damping Off Fungus

Disease that attacks young seedlings and cuttings, causing stems to rot at the base; over-watering is the main cause of damping-off.


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

Damping Off Fungus

Disease that attacks young seedlings and cuttings, causing stems to rot at the base; over-watering is the main cause of damping-off.

Dissolved Solids or Total Dissolved Solids

The amount of dissolved solids, usually fertilizer salts, that are measured in water in parts per million.

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 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.

Ebb and Flow (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.

Foliar Feeding

Misting plants with fertilizer solution, which is absorbed by the foliage.


A product that destroys or inhibits the growth of 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.


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

Harden Off

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


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


The offspring from two plants of different breeds, variety or genetic make-up.

Hydrated Lime

Instantly soluble lime is used to raise or lower pH.


An instrument used to measure relative humidity in the atmosphere.

Leaf Curl

Leaf malformation due to over-watering, over fertilization, lack of magnesium, insect or fungus damage or negative tropism.


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


Also referred to a TRACE ELEMENTS, including S, Fe, Mn, B, Mb, An and Cu.


The substrate or soil less material which supports the plant and absorbs and releases the nutrient solution in hydroponic horticulture.


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

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.


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.


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 5.5; 6.5 is considered ideal. If the pH is not within the acceptable range, nutrients may not be absorbed to maximum capacity.


Sand or volcanic glass which has been expanded by heat, perlite holds water and nutrients on its many irregular surfaces. Also used as a Mineral soil amendment or as nourishment in a hydroponic system.


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


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.


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


Natural insecticide made from the blossoms of various chrysanthemums.


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


Inert, soil less growing medium consisting of woven, thin strand-like fibers made from molten volcanic rock and limestone, which is heated to over 1600°C, extruded, and formed into slabs, cubes and blocks.


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).


A small hair or other outgrowth from the epidermis of a plant, typically unicellular and glandular.


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.


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.