Acid: This is the term for a media or solution with a pH less than 7.0 and is measured using a digital pH meter or with litmus paper

Aeration: The method of adding air or oxygen to a root zone or a nutrient solution

Aeroponics: A method of growing plants in which the roots are supplied with necessary nutrients via misting with a nutrient solution that is pumped through sprayers

Alkaline: This is the term for a media or solution that has a pH greater than 7.0 and is also referred to as basic

Amendment: Changing the composition of a growing media to improve the structure, nutrient content, water holding capacity, cation exchange capacity, or air porosity

Auxin: A plant hormone that promotes root development and stem elongation. The plant created form is known as indole acetic acid (IAA) while the synthetically produced form is indole-butyric acid (IBA).

Bacteria: Single celled microorganisms that can be beneficial or harmful to plant growth depending on the species and their function with respect to plants

Beneficial insects/microorganisms: These organisms work synergistically with plants to defend against harmful insects and diseases and to increase uptake of plant nutrients

Buffering capacity: The ability of a media or solution to resist change in pH fluctuations

Carbon Dioxide: As known as CO2, this odorless gas is an integral part of plant growth and can increase the amount of photosynthesis that a plant has the capacity to do at given light levels if the CO2 level is increased up to 1500ppm. Ambient air is in the range of 300-400ppm.

Carbohydrate: A combination of carbon, hydrogen and oxygen. Sugars and starches are the most commonly used to feed root zone microorganisms

Chelate: A molecule that bonds with minerals to increase the uptake into the plant and prevents interactions with other minerals that could render the mineral unavailable

Chlorosis: General yellowing of a plant due to lack of chlorophyll production during photosynthesis. This is typically related to pH, nitrogen deficiency, or iron deficiency

Compost: Decayed organic matter from plant or animal sources that can provide plants with nutrients needed for growth

Cotyledon: The first "leaves" of a dicot plant that emerge when a seed is planted and serve as the nutrient source until the plant develops roots for uptake of minerals

Cutting: A portion of the plant that is cut off to generate a new, identical plant by rooting

Damping Off: A term that is applied to a dieback of cuttings and seedlings caused by the disease pythium

Dioecious: A plant that has male and female organs on separate plant, ie one plant makes the flowers (female) and one plant makes the pollen (male)

EC meter: A device that measures the electrical conductivity of a solution or media. This is helpful to determine concentration of nutrients or salts affecting plant growth

Electrode: A conductor that establishes an electrical arc with a non-metallic part of the circuit

Elongation: When a plant begins to grow taller or longer creating greater distance between the internodes of the plant

Feed: To supply nutrient to plants via a solution or a dry fertilizer

Fertigation: Supplying the fertilizer to a plant via the irrigation water

Foliage: The leaves of a plant

Foliar Feeding: Spraying or misting the plant leaves with nutrients that the plant can absorb

Fulvic acid: A liquid part of humus that is light golden in color and has the ability to increase uptake of nutrients into plant tissues

Gene: The part of the plant's makeup that determines it capability for production and resistance to disease

Gypsum: A naturally occurring mineral complex that is used to lower the pH of a growing media

Hormone: A chemical that controls the growth and development of plants: auxins, cytokinens, gibberellins, ethylene, and abscisic acid

Humidity: The amount of water in a given volume of air at a given temperature relative to the maximum amount of water it could hold

Humic acid: The liquid portion of humus that comes from decomposed organic matter

Hygrometer: A device that measures relative humidity

Inert: A solution or media that is chemically non-reactive

Leaching: Dissolving or washing out soluble salts from a growing media

Leaf curl: Malformation of a leaf due to over/under fertilization, over-watering, or damage caused by insects or disease

Lime: A naturally occurring mined mineral complex that will raise the pH of a growing media

Litmus paper: A chemically sensitive paper that is used to determine pH

Lumen: A unit of measurement of light that is used to rate the output of light based on the input of electrical watts

Macronutrient: A classification of the major nutrients required for plant growth: nitrogen, phosphorus, potassium, calcium, magnesium

Micronutrients: A classification of the minor nutrients required for plant growth also known as trace elements: iron, boron, copper, molybdenum, zinc, manganese, nickel, and cobalt

Moisture meter: A device that measures the amount of moisture in a growing media or soil

Nanometer (nm): 0.00000001 of a meter, used as a scale to measure wavelengths of light spectrums

Nutrient: A mineral that a plant can uptake and assimilate into its tissue, plant food

Organic: Carbon based. In horticulture, organic means natural. Organic fertilizers are made in nature, not in chemistry labs

Peat moss: Moss that is slowly decayed in conditions of extreme moisture and low temperatures

pH: the power of hydrogen. This is a scale of 1 to 14 that expresses the number of free hydrogen ions in solution. Most plants grown hydroponically thrive at a pH between 5.5 to 6.3.

pH meter: an electronic device that measures pH

Photoperiod: The length of light during a 24 hour period

Photosynthesis: The conversion of light energy to chemical energy (carbohydrates) by plants

Propagate: To grow a new plant by taking a cutting from an existing plant and rooting the cutting or by germinating a seed

Prune: Altering a plant by cutting leaves, stems, shoots, flowers, or fruits

Rhizosphere: The area directly surrounding the roots of a plant. This area is where beneficial microorganism thrive

Rockwool: A growing media that is made from fibers created by heating volcanic rock at high temperatures

Root bound: When the roots of a plant are inhibited from normal growth from being confined in a container

Salt: An ionic compound whose cation comes from a base and whose anion comes from an acid. Buildup of salts in growing media can cause plants to burn

Soluble: Able to be dissolved into water

Starch: A complex carbohydrate that is manufactured by plants and stored

Stomata: An opening in the leaves of the plant through which the plant takes up nutrients, releases water, and takes up CO2

Sugar: A simple carbohydrate that is manufacture by plants via photosynthesis

Tap Root: The main root of a plant that grows from the seed. The lateral roots form from the tap root.

Transpire: The plant releasing water through the somata

Trellis: A frame or netting that trains or supports plants

Ultraviolet (UV): Short wavelengths of light that exist outside of the visible spectrum past blue and violet

Wetting agent: A compound that reduces the surface tension of water making it easier for a media to absorb