Glossary of Horticultural Terms

A

Alternating current (ac): an electric current that reverses its direction at regular occurring intervals. Homes have ac.

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. Tomatoes are examples of annuals plants.

Arc: luminous discharge of electricity (light) between two electrodes.

Arc tube: a quartz container for luminous gases also houses the arc in hid lights.

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

B

Bacteria: very small, one-celled organisms.

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

Biodegradable: able to plants 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 jacket that protects the arc tube of an hid lamp.

Bulbs: common are tulips and daffodils planted in the fall for spring blooms, or forced indoors for winter blooms.

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C

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 the 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, etc., 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 indoors for winter blooms. Common varieties are dahlias and irises.

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.

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D

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.

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.

Dry ice: a cold, white substance formed when carbon dioxide is compressed and cooled; dry ice changes into co2 gas at room temperature.

E

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

Elongate: grow in length.

Envelope: outer protective bulb or jacket of a lamp.

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

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F

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

Female: pistillate, ovule, seed-producing.

Fertigate: 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 a 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. The foot-candle is equal to one lumen per square foot. Foot-candle is a derived unit of illuminance from lux. One foot-candle is equal to 10.76 lux.

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 overloaded.

Fuse box: box containing fuses that control electric circuits.

G

Gpm: gallons per minute.

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.

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H

Halide: binary compound of a (halogens) with an electropositive elements.

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.

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

Hood: reflective cover of a hid lamp.

Hor: the abbreviation stamped on some hid bulbs meaning they must be burned in a 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 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: 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.

I - J - K

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 lamp.

Kilowatt hour: measure of electricity used per hour; a 1000-watt hid uses one kilowatt in one hour.

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L

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 chloroplasts in the cells which contain chlorophyll.

LeD: Light Emitting Diode

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.

Light mover: a device that moves a lamp back and forth or in a circle 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, silt 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.

M

Macro nutrient: one or all of 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 plants 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 inch

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, etc.; indoors, mulch keeps soil too moist and possible fungus could result.

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N

Nanometer: .000000001 meter, nm is used as a scale to measure wave lengths 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.

O

Ohm's power law: a law that expresses 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 as well as animal life.

P

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 range of 5.5 to 6.8 ph.

Ph tester: electronic instrument or chemical used to find where soil or water is on the ph scale.

Photometrics: 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 part towards a light source.

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

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

Power surge: interruption or change in intensity of electricity.

Primary nutrients: n-p-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.

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R

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.

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 new vegetative growth.

S

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 be dissolved in water.

Spore: seed like offspring of a fungus.

Sprout: 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 hydrocarbon chain.

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

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T

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.

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 by products via 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.

U - V - W

Ultraviolet: light with very short wave lengths, 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 the water, making it wetter.

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.