Alternative Current (AC) – An electric current that reverses its direction at regular recurring intervals. 

Acid – An acid or sour substance has a pH below 7.

Aeration Supplying soil and roots with air or oxygen.

Aeroponics – Growing plants by misting roots suspended in air.

Alkaline – Refers to a substance with high pH; any pH over 7 is considered alkaline.

All-Purpose (General-Purpose) Fertilizer – A balanced blend of N-P-K; All-purpose fertilizer is used by most growers.

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

Ampere (Amp) – The unit used to measure the strength of an electric current.

Annual – A plant that normally completes it entire life cycle in one year or less.

ANSI – American National Standards Institute requires a specific code be printed on the lamp and on the corresponding ballast.  These codes must match in order for the system to operate properly.

Arc – Luminous discharge of electricity (light) between two electrodes.

Arc Tube – A quartz container for luminous gases also house the arc in HID lights.

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.

Beneficial Nematodes – Microscopic organisms that seek out and destroy more than 230 different kinds of soil dwelling and wood boring insects.

Biodegradable – Able to decompose or break down through natural bacterial or fungal action, substances made of organic matter are biodegradable.

Bolt – Term used to describe a plant that has gone to seed prematurely.

Bonsai – A very short or dwarfed plant.

Breaker Box – Electrical circuit box having on/off switches rather than fuses. 

Breathe – Roots draw in or breathe oxygen, stomata draw in or breathe carbon dioxide.

Bud blight – A withering condition that attacks flower buds.

Buffering – The ability of a substance to reduce shock and cushion against pH fluctuations.

Bulb – The outer glass envelope or jacked that protects the arc tube of an HID lamp.

Bulbs – Common are tulips and daffodils planted in the fall for spring blooms, or forced indoor for winter blooms.

Calyx – The pod harboring female ovule and two protruding pistils, seed pod.

Carbon Dioxide (CO2) – A colorless, odorless, tasteless gas in the air necessary for plant life and biomass accumulation.

Carbohydrate – Neutral compound of carbon, hydrogen and oxygen.  Sugar, starch and cellulose are carbohydrates.

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, that houses it’s DNA.

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 – Chemical used to purify water.

Chloroplast – Containing chlorophyll.

Chlorosis – The condition of a sick plant with yellowing leaves due to inadequate formation of chlorophyll.  Chlorosis is caused by nutrient deficiency, usually iron or imbalanced pH.

Clay – Soil made of very fine organic mineral particles.  Clay is not suitable for container gardening.

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

Color Spectrum – The band of colors (measured in nm) emitted by a light source.

Color Temperature – The relative whiteness of a piece of tungsten steel heated to that temperature in degrees Kelvin.

Color Tracer – A coloring agent added to many commercial fertilizers, so horticulturist knows there is 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 for example, along with other plants to discourage insect infestation. 

Compost – A mixture of decayed organic matter.

Core – The transformer in the ballast is referred to as the core in HID lighting systems.

Corms, Rhizomes, and Tubers – Dormant stems planted in the fall for spring blooms, or forced indoor for winter blooms.  Common varieties are dahlias and irises.

Cotyledon – Energy storage components of a seed that feed the plant before the emergence of leaves. 

Cross-Pollinate – Pollinating two plants having different ancestry.

Crytolaemus – Commonly known as “Mealybug Destroyer”, they have a voracious appetite for mealybugs.  Like small ladybugs with an orange head and tall black body.  Their first choice is mealybugs, but they also eat aphids, immature scale and immature whitefly.

Cubic Foot – Volume measurement in feet: L”x W”x H”/ 1728” = Cu. Ft.

Cutting – Growing tip cut from a parent plant for asexual propagation.  Clone.

Damping-Off - Disease that attacks young seedlings and cuttings causing stem to rot at base.

Direct Current (DC) – An electric current that flows in only one direction.

Delphastus – A small black beetle that feeds on several species of whitefly larvae including greenhouse, sweet potato, and avocado whitefly.  When out of whitefly larvae, they will feed on spider mites.  Both beetle and larvae are predators and will eat whitefly eggs and larvae, but not adult whiteflies.

Deplete - Exhaust soil of nutrients, making it infertile.

Desiccate - Cause to dry up.  Insecticidal soap desiccates its victims.

Dioecious - Having distinct male and female organs on different plants within the same species.

Dome - The part of the HID outer bulb opposite the neck and threads.

Dome Support - The spring like brackets that mount the arc tube within the outer envelope.

Drainage - Way to empty soil of excess water, with good drainage, water passes through soil evenly.

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

Drip System - A very efficient watering system that employs a main hose with small water emitters.

Electrode - A conductor used to establish electrical arc or contact with non-metallic part of a circuit.

Elongate - Growth in length.

Envelope - Outer protective bulb or jacket of a lamp.

Equinox - The point at which the suns crosses the equator and day and night are 12 hours long; the equinox occurs twice a year, in spring and fall.

Feed - Deliver nutrient to the plant via roots or foliage.

Female - Pistillate, ovule, seed producing.

Ferreting - To fertilize and irrigate at the same time.

Fertilizer burn - Over fertilization, first leaf tips burn (turn brown) then the leaves curl.

Flat - Shallow (three inch) deep container, often 18 by 24 or 10 by 20 inches with good drainage, used to start seedlings or cuttings.

Fluorescent Lamp - Electric lamp using a tube filled with fluorescent material, which has a low heat output.

Foliage - The leaves or more generally, the green part of the plant.

Foliar Feeding - Misting fertilizer solution, which is absorbed by the foliage.  Best to do when first turning on your lights.

Foot-Candle - The unit is defined as the amount of illumination that the surface of an imaginary 1-foot radius sphere would be receiving if there were a uniform point source of one candle in the exact center of the sphere. 

Fungistat - A product that inhibits fungus keeping it in check.

Fungus – A lower plant lacking chlorophyll which may attack green plants; mold, rust, mildew.

Fuse - Electrical safety device consisting of a metal that melts and interrupts the circuit when circuit is overload.

Fuse Box - A box containing fuses that control electric circuits.

GPM - Gallons per minute.

Gene - Part of the chromosome that influences the development of plant; genes are inherited through sexual propagation.

Genetic Make Up - The set of genes inherited from parent plants.

Halide - Binary compound of halogens with an electropositive element.

Hermaphrodite - One plant having both male and female organs; 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.

HID - High Intensity Discharge lamp.

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

Hood - Reflective cover of a HID lamp, which directs the light towards plants.

HOR - The abbreviation stamped on some bulbs meaning they must be burned in horizontal position.

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.

Humidity (relative) - Ratio between the amounts 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 - An offspring from two plants of different breeds, variety or genetic make up.

Hydrated Lime - Instantly soluble lime, used to raise pH or sweeten soil.

Hydrogen - Light or colorless, odorless gas; hydrogen combines with oxygen to form water.

Hygrometer - 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.

Intensity - The magnitude of the light energy per unit; intensity diminishes the farther away from the source.

Jacket - Protective outer bulb or envelope of a lamp.

Kilowatt Hour - Measure of electricity used per hour; a 1000-watt hid uses one kilowatt per hour.

Lacewing - Beneficial insects that preys on aphids.

Leach - Dissolve or wash out soluble components of soil by heavy watering.

Leaf Curl - Leaf malformation due to over-watering, 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 chloroplast in the cell, which contain chlorophyll.

LEC (Light Emitting Ceramic) metal halide - Ceramic metal halide high intensity discharge lighting is the next generation of the traditional metal halide lighting, offering longer life, improved lumen characteristics and energy savings.

LED - Light-Emitting Diode:  a semiconductor diode that emits light when conducting current and is used in electronic equipment, especially for displaying readings on digital watches, calculators, lights, ect.

Leggy - Abnormally tall internodes space, with sparse foliage.  Leggyness caused by a lack of blue light or CO2.  Too much nitrogen can also cause this.

LEP (Light Emitting Plasma) - Plasma, the fourth state of matter is a type compact long life lighting source powered by a radio frequency.

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.

Light Mover - A device that moves a lamp and forth or in a cycle across the ceiling of a garden room to provide more even distribution of light.

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, salt and sand.

Lumen - Measurement of light output: one lumen is equal to the intensity of light emitted by one candle that falls on one square foot of surface located one foot away from one candle.

Macro Nutrient - One or all the primary nutrients N-P-K or the secondary nutrients magnesium and calcium.

Mean - Average throughout life; HID’s are rated in mean lumens.

Meristem - Tip of plant growth.

Micro Nutrient - Also referred to as trace elements, including S, Fe, Mn, B, Mo, Zn, and Cu.

Millimeter - Thousandth of a meter approximately .04 inches.

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

Monochromatic - Producing only one color; LP sodium lamps are monochromatic.

Mulch - A protective covering of organic compost, leaves, ect. Indoors, mulch keeps soil too moist and possible fungus could result.

Nanometer - .000000001 meters, nm is used as a scale to measure wavelengths of light; color and light spectrums are expressed in nanometers (nm).

Necrosis - Localized death of a plant part.

Neck - Tubular glass end of the HID bulb, attached to the threads.

Nutrient - Plant food, essential elements N-P-K, secondary and trace elements fundamental to plant life.

Ohm’s Power Law - A law that express the strength of an electric current; volts times amperes equals watts.

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”.

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, which completes its life cycle over several years.

pH - A scale from 1 to 14 that measures the acid to alkaline balance of a growing medium (or anything); in general plants grow best in a 5.5 to 6.8 pH.

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

Photometric - The study of light, especially color.

Phosphor Coating - Internal bulb coating that diffuses light and is responsible for variations in color outputs.

Photoperiod - The relationship between the length of light and dark in a 24-hour period.

Photosynthesis - The building of chemical compounds (carbohydrates) from light energy, water and carbon dioxide.

Phototropism - The specific movement of a plant towards a light source.

Pigment - The substance in paint or anything that absorbs light, producing (reflecting) the same color.

Pollen - Fine, dust like microspores containing male genes.

Power Surge - Interruption or change in intensity of electricity.

Primary Nutrients – Nitrogen (N), Phosphorus (P), Potassium (K).

Propagate - (1) Sexual: Produce a seed by breeding different male and female flowers.  (2) Asexual: To produce a plant by taking cuttings.

Prune - Alter the shape and growth pattern of a plant by cutting stems and shoots.

PVC Pipe - Plastic (polyvinyl chloride) pipe that is easy to work with, readily available and used to pipe water into a garden room.

Pyrethrum - Natural insecticide made from the blossoms of various chrysanthemums.

Root Bound - Roots stiffed 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.

Rejuvenate - Restore youth; a mature plant, having completed its life cycle (flowering), may be stimulated by a new 18 hour photo period, to rejuvenate or produce vegetative growth.

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).

Seed Pod - A dry calyx containing a mature or maturing seed.

Short Circuit - Condition that results when wires cross and form a circuit.  A short circuit will blow fuses.

Socket - Threaded, wired receptacle for a bulb.

Soluble - Able to dissolve 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.

Stroboscopic Effect - A quick pulsating or flashing of a lamp.

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 the hydrocarbon chain.

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

Tap Root - The main or primary root that grown the seed; lateral roots will branch off the taproot.

Tepid - Warm 70 to 80 degrees F (21 to 27 degrees C); always used tepid water around plants to facilitate chemical processes and ease of shock.

Terminal Bud - Bud at the growing end of the main stem.

Thin - Cull or weed out weak, slow growing seedlings.

Transformer - A device in the ballast that transforms electric power from one voltage to another.

Transpire - Give off water vapor and bi-products via the stomata and carbon dioxide intake at the leaves.

Trellis - Frame or netting (lattice) that trains or supports plants.

Tungsten - A heavy, hard metal with high melting point which conducts electricity well; tungsten is used for a filament in tungsten halogen and incandescent lamps.

Ultraviolet - Light with a very short wave length, out of the visible spectrum, past the blue-violet.

Variety - Strain, phenotype.

Vent - Opening such as a window or door that allows the circulation of fresh air.

Ventilation - Circulation of fresh air, fundamental to a healthy indoor garden, an exhaust fan creates excellent ventilation.

Vertical - Up and down, perpendicular to the horizontal.

Wetting Agent - Compound that reduces the droplet size and lowers the surface tension of water, making it easier for the plant to use.

Wick - 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.