Have you ever wondered what is involved in Hydroponic gardening? In order to understand how to use hydroponics for gardening you will need to understand the terminology of the various parts. You will notice that some of these terms are similar to regular gardening as well.
Abscisic acid - Plant hormone that facilitates vegetative bud dormancy, seed maturation, & leaf abscission (leaf drop).
Acid - Any of various water-soluble compounds having a sour taste and pH below 7, and capable of turning litmus red.
Aerobic - Depending on free oxygen or air
Aeroponic - A hydroponic method that may or may not contain media which delivers the nutrient solution to the root zone via a mist or a fog.
Aeroponics - a variation of hydroponics that involves the misting of plant roots with nutrient solution.
Algae - Primitive chlorophyll-containing mainly aquatic eukaryotic organisms lacking true stems and roots and leaves
Alkaline - Relating to or containing an alkali, having a pH greater than 7.
Allele - different forms of the same gene; allele "A" may produce a tall plant, while allele "a" gives a short plant.
Amino Acid - Organic compounds containing an amino group and a carboxylic
acid group: "Proteins are composed of various proportions of about 20 common amino acids".
Ampere - The basic unit of electric current adopted under the Systeme International d'Unites; "A typical household circuit carries 15 to 50 amps".
Anerobic - Living or active in the absence of free oxygen: "Anaerobic bacteria"
Annual plant - A plant that completes its entire life cycle within the space of a year
Anther - part at the top of the male flower that produces the pollen.
Aphid - Any of various small plant-sucking insects
Apical Dominance - Understanding the principle of apical dominance is helpful when embarking upon any regimen of tree or other plant management. Plants form new tissue in an area called the meristem, located near the tips of roots and shoots, where active cell division takes place. Meristem growth is aimed at ensuring that leaves are quickly elevated into sunlight, and that roots are able to penetrate deeply into the soil. Once adequate height and length are achieved by the stems and roots, they will begin to thicken to give support to the plant. On the shoots, these growing tips of the plant are known as apical buds. The apical bud (or tip) produces the growth, which not only promotes cell division, but also diffuses downwards and inhibits the development of lateral bud growth (“Side shoots"), which would otherwise compete with the apical tip for light and nutrients. Removing the apical tip and its suppressive hormone, allows the lower dormant lateral buds to develop, and the buds between the leaf stalk and stem produce new shoots, which compete to become the lead growth. Manipulating this natural response to damage (known as the principle of apical dominance) by processes such as pruning allows the horticulturist to determine the shape, size, and productivity of many fruiting trees and bushes.
Apical Meristem - (See Apical Dominance)
Aquaponics - the integration of aquaculture (the raising of marine animals, such as fish) with hydroponics; the waste products from the fish are treated and then used to fertilize hydroponically growing plants.
Asexual reproduction - The propagation of a plant by cutting, division, layers, grafts, or other vegetative means, rather than by seeds. Used to produce plants that will be like their parent, and is sometimes called cloning.
Auxin - A hormone found in plants that induces growth and fructification even if the plant hasn't been pollinated (seedless watermelon is an example); also the predominate hormone used when rooting cuttings: example IBA & NAA.
Axillary - In reference to an axillary bud. When a leaf attaches to the main trunk, an angle is formed between the stem & leaf. This angle is called the axil. A vegetative/reproductive bud may be present between this angle; this vegetative/reproductive bud is called an axillary bud.
B-1. - Also called Thiamine, this vitamin helps plants use stored energy in stressful conditions when they normally could not.
Bacillus subtillus - A species of Bacillus found in soil and decomposing organic matter; some strains produce antibiotics
Bacillus thuringiensis - A naturally occurring bacterium present in soil, which has been used successfully by home gardeners and organic farmers to control certain insects for more than 30 years. When ingested by these insects, a protein produced by B.T. interferes with the insect’s digestion, and acts as an insecticide.
Bacteria . - Is a single celled organism belonging to the domain bacteria, in the three domain scheme. It can also be a type of organism belonging to one of the three major branches of. Traditionally classified as one of the five kingdoms, bacteria are microscopic and relatively simple cells. They lack the nucleus and organelles of the more complex cells called "eukaryotes;" however, like the cells of plants, most possess a carbohydrate based. In common speech, "bacteria" still refers also to archaebacteria, although the latter recently have been classified as an independent branch or "domain" of life. There are malicious & beneficial bacteria, so not all bacteria are destructive, but all are characterized by the “slime" they produce once an infection has occurred.
Bacterial soft rot. See Botrytis.
Ballast - The “transformer" of a lighting system, which provides the energy necessary for an HID bulb to ignite.
Basal - At the bottom or base of a plant. A basal shoot is a limb growing near the ground. A basal cut is made at the bottom of a cutting.
Base up lamp - A vertically oriented HID lighting system where the base of the bulb (threaded end) is in essence hanging down.
Basic - (see alkaline)
Beneficials - Alluding to the beneficial organisms that are responsible for the transformation of organic materials into nutrients and other compounds that are used for plant growth. Example: Types of bacteria, fungi, protozoa, nematodes, micro-arthropods, and mycorrhizal fungi.
Biennial plant - A biennial plant lives for two years, with the vegetative stage occurring in year one and the reproductive stage (flowering) occurring in year two.
Biological insect control - In essence, the use of one species of insect against another more harmful insect. Example: Using ladybugs for controlling a heavy aphid infestation.
Blood meal - A type of organic nitrogen that is derived from the drying of livestock blood.
Blossom end rot - A physiological deficiency symptom in which a plant has not been provided the proper amounts of Calcium, which is crucial in cell wall maintenance. This symptom appears as a black water-soaked area on the bottoms of tomato fruit.
Blue Light - (See Wavelength)
Bolting - for a plant to prematurely begin the development of a flowering stalk and, subsequently, seed.
Bone meal - An organic fertilizer made of ground livestock bones that typically contains moderate amounts of Calcium and Magnesium, and relatively high amounts of Phosphorus.
Boron - One of the seven micronutrients, Boron is believed to be involved in carbohydrate transport in plants. Boron also assists in metabolic regulation. Boron deficiency will often result in bud dieback.
Botrytis - Also known as grey mold or the Noble Rot (viniculture). , A fungal disease that is promoted by cool, moist weather. Symptoms appear as water soaked, blighted areas on flowers, stems or leaves with a moldy gray growth, hence the common name. Control by removing all infected plant parts and making sure the plants have sufficient room so that good air circulation is maintained around them.
Botrytis - any of several fungal diseases that afflict plants; commonly called bacterial soft rot or gray mold.
Breeding - The production of animals or plants by inbreeding or hybridization.
Bud - A protuberance on a stem, from which a flower, leaf or shoot develops.
Bud rot - (See Botrytis)
Bulb (lighting) - An artificial light source - a light bulb or tube, the correct term is lamp, but “Bulb" is a more common term for the home user
Bulb (plant) - A bulb is not a root; it is an underground stem that functions as a food storage organ. Think of the onion-- each layer is a modified underground basal leaf, called a scale, closely adhered to the stem to protect it, as well as store additional food. Plants producing bulbs are all perennials.
Calcium - A secondary macroelement which provides an important component of cell walls, participates in the maintenance of membrane permeability and structure, and it is also known to activate some enzymes. Symptoms of calcium deficiency include tip dieback of buds and new leaves.
Callus - A cluster of undifferentiated plant cells that have the capacity to regenerate a whole plant in some species.
Cambium - Layer of living cells between the wood and the innermost bark of a tree. Each growing season the cambium adds a new layer of cells (by cell division) on the wood already formed, as well as a layer of inner bark on the cambium's outer face. Division of these cells results in diameter growth of the tree through formation of wood cells (xylem) and inner bark (phloem).
Capillary action - Movement of water along microscopic channels. This movement is the result of two forces: the adhesion and absorption of water to the walls of the channels; and cohesion of water molecules to each other. When the surface of a liquid is in contact with a solid, the liquid is elevated or depressed depending upon the relative attraction of the molecules of the liquid for each other or for those of the solid. This is similar to how plants seemingly defy gravity when they transport liquid from the roots upward through the plant.
Carbohydrates - Starches and sugars manufactured by a plant and used to provide energy for metabolism, and structural compounds for growth.
Carbon - A major component of organic molecules, which are the building blocks of all organisms. Humans breath air, plants "breath" carbon dioxide. Carbon dioxide supplies the carbon necessary for plant health. Plants growing outdoors will not be deficient in carbon.
Carbon Dioxide - A greenhouse gas whose atmospheric concentrations have been continually increasing from its pre-industrial (1750-1800) levels of 280 parts per million (ppm). It is currently increasing at a rate of 1.3-1.6 ppm per year, with a concentration (1995) ranging from 356-360 ppm, depending on location. There is a natural seasonal cycle in carbon dioxide levels in the atmosphere; CO2 decreases in summertime when plant productivity consumes CO2, and an increase in winter when biota are less active and respiration exceeds photosynthesis.
Catalyst - A substance that increases the rate of a chemical reaction, without being consumed or produced by the reaction. Enzymes are catalysts for many biochemical reactions
Causal agent - Any entity that causes events to happen. Example: Fungal infection causing Verticilium wilt. The fungus is the causal agent.
Cell - The basic structural and functional unit of all organisms; cells may exist as independent units of life, or may form colonies of tissues as in higher plants and animals.
Chelate - Organic chemical that forms ring compound in which a metal ion is held between two or more atoms strongly enough to diminish the rate at which it becomes fixed by soil, thereby making it more available for plant and microbial uptake.
Chlorophyll - The green pigment in plants that is created in the presence of light, which is necessary for photosynthesis to occur.
Chlorosis - The discoloration of normally green plant parts that can be caused by disease, lack of nutrients, or various air pollutants.
Citric Acid - An organic acid naturally occurring in citrus fruits used to adjust the pH of products, and nutrient solutions.
Cladosporium - any of several fungal diseases that afflict plants; commonly called leaf mold.
Clay - A very fine grained material, smaller than silt (clay has a diameter of less than 1/256 mm). Clay is formed by the weathering and breaking down of rocks and minerals.
Clone - A clone is a genetically identical group of plants derived and maintained from one individual by vegetative propagation.
Closed system - a hydroponic system, like nutrient film technique (NFT) systems, that recirculates the nutrient solution.
Coconut coir - Fiber made by cracking the outer brown husk of the coconut, shredding it into coarse fibers, then twisting or weaving them. Used for doormats, household brushes. Coconut coir is rot-resistant and naturally durable.
Cold frame - Cold frames are like small greenhouses, creating a microclimate around the plants inside. They serve to protect plants from frost or to harden-off seedlings in the spring. Any number of materials can be used, but generally, wood is used to create a box-like, open bottomed frame. A hinged lid can be opened to allow in air on hot days. The lid is made mostly of glass (or clear plastic) to allow in light. The soil is warmed by the sun during the day and then releases the heat into the confines of the cold frame at night, protecting the plants inside from freezing.
Companion planting - Some plants inhibit the growth of others nearby by releasing substances into the soil (called allelopathy). Other plants actually assist neighbours by fixing nitrogen or by repelling insects that attack them (oregano repels the cabbage butterfly for example). Gardeners can profit by being aware of these relationships.
Compost - Process whereby organic wastes, including food wastes, paper, and yard wastes, decompose naturally, resulting in a product rich in minerals. Compost is ideal for gardening and farming as a soil conditioner, mulch, resurfacing material, or landfill cover.
Compost tea - A water extract of compost that is brewed, usually in water. Organisms extracted from the compost, including bacteria, fungi, protozoa and nematodes are given a chance to increase in number and activity using the soluble food resources and nutrients present in the water. An enormous diversity of bacteria, fungi, protozoa and nematodes should be produced, depending on the quality of the compost.
Conductivity factor - A unit used in calculating fertilizer concentration. Example: 1 CF = 64 ppm (parts per million).
Conductivity - the scale, described as electrical conductivity (EC) or conductivity factor (CF), that is used to measure the strength of nutrient solution.
Convertible - (See Switchable)
Copper - One of the seven micronutrients essential for plant growth. It is a component of some enzymes and of vitamin A. Symptoms of copper deficiency include browning of leaf tips and chlorosis.
Corm - The bulblike underground part of a stem, as found on crocus or gladiolus.
Cotyledon - The "seed leaves" produced by a seed plant embryo. They serve to absorb nutrients packaged in the seed, until the seedling is able to produce its first true leaves and begin photosynthesis. The number of cotyledons is a key feature for the identification of the two major groups of flowering plants.
Cover crop - Cover crops will often include leguminous plants like clover and vetch, but they might also be grains like rye or oats. Cover crops are often planted as a green manure, but they also serve to prevent erosion, control weeds, and conserve water in the soil (from losses due to evaporation).
Cross-pollination - transferring pollen from the flowers of one plant of a species to the stigma of another plant of the same species.
Crown - The upper branches and leaves of a tree.
Cultivar - A cultivated variety of a plant selected for some feature that distinguishes it from the original species from which it was selected.
Cultivation - The process of preparing the land and caring for growing crops.
Cutting - (See Clone)
Cytokinin - Any of a class of plant hormones that promotes cell division and delays the senescence (aging) of leaves.
Damping off - Any of a number of fungal diseases which attack seedlings, causing the stem to wither at the soil line, collapsing the whole plant. There is no good cure for affected plants, but removing all the diseased material and moving the seedlings to a warm, bright, airy location can save any remaining plants. Proper thinning and avoidance of over watering, especially during cloudy periods is the best preventive measure.
Dark reactions - A process found in all plants and animals: A series of enzymatic reactions in mitochondria involving oxidative metabolism of acetyl compounds (sugars made during photosynthesis) to produce high-energy phosphate compounds that are the source of cellular energy.
Day length - The duration of lighting cycle where there is enough light to perform photosynthesis. Example: For an 18 hour on and 6 hour off lighting cycle, the day length equals 18 hours.
Day neutral plants - Plants that flower regardless of day length.
Deficiency - A sub-optimal level of either one or more nutrients, often resulting in poor health.
Deficiency. See mineral deficiency.
Desiccate - A process that loses water or moisture.
Dicot - A subdivision of flowering plants whose members possess two embryonic seed leaves, or cotyledons.
Dioecious - varieties or species with male and female flowers on separate plants.
Disease - Any condition that interrupts normal plant physiology that is caused by irritation by a primary causal agent that results in the formation of symptoms.
Dominant - A heritable character possessed by one parent of a hybrid which, when pure, will express itself in the hybrid to the apparent exclusion of the opposite or recessive character in the other parent. Also, a species that comprises the majority of biota in an ecosystem.
Dormancy - The resting or inactive phase of plants or seeds. Dormancy of shoots is usually in response to unfavorable environmental conditions. The breaking of seed dormancy requires moisture, sometimes cold temperatures and/or abrasion of the seed coat.
Downy mildew - Any of various fungi of the family Peronosporaceae parasitic on grapes, potatoes, and melons.
Drip irrigation - An irrigation method where pipes or tubes filled with water slowly drip onto a landscaped or other planted area. Drip irrigation is a low-pressure method of irrigation and less water is lost due to evaporation than high-pressure spray irrigation.
Dry rot. (See Fusarium.)
Early blight - Early blight is a very common
disease of both potato and tomato. It causes leaf spots and tuber blight on potato, and leaf spots, fruit rot and stem lesions on tomato. The disease can occur over a wide range of climatic conditions and can be very destructive if left uncontrolled, often resulting in complete defoliation of plants. In contrast to the name, early blight rarely develops "early", but usually appears on mature foliage.
Ebb and Flow - A type of hydroponic system where potted plants are held in a tray, which is periodically flooded with a nutrient solution and then drained.
Electrical Conductivity - Measure of the total concentration of dissolved salts in the water. When salts dissolve in water they give off electrically charged ions, these ions conduct electricity.
Electrical conductivity. See conductivity.
Embryo - An animal or plant in the early stages of its development; in plants, the stage in the seed before the beginning of rapid growth.
Emulsion - A suspension of droplets of one liquid in another liquid (such as oil and water). The two liquids do not actually combine but are instead suspended within one another.
Enzyme - A protein that acts as a catalyst, speeding the rate at which a biochemical reaction proceeds, but not altering the direction or nature of the reaction. Enzymes aren't consumed in the reaction.
Epinasty - That state in which more rapid growth on one side of a plant organ or part (especially leaf) causes it to bend or curl downward, typically a symptom of certain viral diseases.
Ethylene - A plant growth-regulating gas, naturally produced in ripening fruit as well as other parts of the plant, responsible for promoting ripening and involved in abscission and other plant processes.
Etiolation - The act of causing a plant to develop without chlorophyll by growing it without exposure to sunlight.
Expanded clay - A media that is composed of small clay beads, which are fired to 1,600 °F so they are sterile by way of the manufacturing process. They can easily be cleaned and reused.
F1, F2, F3, etc. - the F1 generation is the result of crossing two different varieties; a cross of two F1 plants produces F2 seed; and so on.
Fatty acids - Most common form of lipids found in all cells. Come in saturated (reduced) and unsaturated (oxidized) form and are a component of phospholipids and fats. Plants have the ability to breakdown fatty acids for needed energy.
Filament - see stalk.
Fish emulsion - (see Emulsion)
Flood and Drain - (See Ebb and Flow)
Flower - The flower is the reproductive organ of the plant. It contains both the female and male parts, but some are incomplete, having only one or the other.
Fluorescent light - A glass tube filled with a mixture of gases at low pressure. Emits ultra-violet radiation converted to light by the fluorescent coating inside the tube. A flourscent lamp is energy efficient.
Foliar feeding - Fertilization of a plant through its leaves by use of a water-soluble fertilizer sprayed directly onto them.
Frost free date - A yearly average of the last frost free days, which gives an indication of when it is safe to plant outdoors.
Fruit - In flowering plants, the structure which encloses the seeds. True fruits develop from the ovary wall, such as bananas and tomatoes, though not all fruits are edible, such as the dry pods of milkweed or the winged fruits of the maple.
Fulvic acid - A yellow to yellow-brown humic substance that is soluble in water under all pH conditions. Fulvic acid is a short chain molecule derived from humic acid (long chain), so as a result fulvic acid is more stable in hydroponic solutions.
Fungi - Microorganisms that lack chlorophyll. They differ from bacteria by having genetic material arranged on chromosomes, and a membrane surrounding the nucleus. Fungi includes mushrooms, moulds, yeasts and rusts. Many fungi are used in industry: in brewing, baking, to make antibiotics, vitamins and food proteins.
Fungicide - Chemical used to control fungal diseases. Despite the name, most fungicides only slow down or prevent the spread of disease -- only a few actually kill the fungus.
Fungus gnat - Minute blackish gregarious flies destructive to mushrooms and seedlings.
Fusarium wilt - A plant wilt caused by fungi of the genus Fusarium. Tomato, potato, pepper, eggplant, artichoke, beets, broad beans, turnip, radish, cucumber, muskmelon and watermelon are severely affected. Asparagus, bean, broccoli, brussels sprouts, cabbage, cauliflower, celery, chives, collards, garlic, kale, kohlrabi, leek, lettuce, mustard, onion, parsley, peas, rutabaga, spinach and turnip are sometimes affected. Corn, grain and grass are not hosts.
Fusarium - any of several fungal diseases that afflict plants; commonly called dry rot or wilt.
Genus - An assemblage of species, having so many fundamental points of structure in common that in the judgment of competent scientists, they may receive a common substantive name. A genus is not necessarily the lowest definable group of species, for it may often be divided into several subgenera. In proportion as its definition is exact, it is natural genus; if its definition can’t be made clear, it is more or less an artificial genus. Example: The Sweetgum tree’s scientific name is Liquidambar styraciflua; the genus name is Liquidambar, while the specific epithet is styraciflua, and the species name is Liquidambar styraciflua.
Germinate - To cause to sprout or develop.
Germination - the activation of a seed causing it to start to grow; also the production of a pollen tube by a pollen grain
Gibberellic acid - Gibberellic acid is a hormone found in plants that promotes cell elongation (plant and root growth in length or height). When externally applied it will increase the speed at which these growth functions occur. In some crops, like cucumbers and blueberries, externally applied gibberellic acid aids pollination in the absence of bees or during periods of excessively high temperatures that may occur during the normal period of pollination.
Gray mold. See Botrytis.
Green lacewing - Any one of several species of neuropterous insects of the genus Chrysopa and other allied genera. They have delicate lacelike wings and brilliant eyes. Their larvae are useful in destroying aphids. The Green Lascewing is also called the lace-winged fly and golden-eyed fly.
Green Manure - (see Cover crop)
Greensand - A variety of sandstone, usually imperfectly consolidated, consisting largely of glauconite, a silicate of iron and potash of a green color, mixed with sand and a trace of phosphate of lime.
Growing medium - materials that are sometimes used in hydroponic growing to support the plant's roots and, sometimes, to hold nutrient.
Gypsum - A mineral soil amendment, which adds Calcium and Sulfur to the soil without affecting the soil’s pH.
Hard water - When water is referred to as 'hard' this simply means that it contains more minerals than ordinary water. These minerals are usually, but not limited to, calcium and magnesium. The degree of hardness of the water increases when more calcium and magnesium dissolves. Magnesium and calcium are positively charged ions. Because of their presence, other positively charged ions will dissolve less easily in hard water than in water that does not contain these minerals. This is the cause that some soaps do not readily dissolve in hard water, because these ions react with the soap molecules to form soap scum.
Hardening off - Hardening off is the process of adapting a plant that has been grown under protective shelter - indoors or in a greenhouse - to full outdoor exposure. Over a week or more, the plant is exposed to increasing intervals of time outdoors so that when it is planted in the garden it can make the transition with a minimum of transplant shock.
Herb - A plant without a persistent woody stem, at least above ground. A plant with a fleshy stem as distinguished from the woody tissue of shrubs and trees and other plants that do not die back at the end of the growing season.
Herbaceous plant - Generally dies back at the end of each growing season.
Herbicide - A chemical substance used to prevent, inhibit, or destroy non-woody plant growth. If its effectiveness is restricted to a specific plant or type of plant, it is known as a selective herbicide. If its effectiveness covers a broad range of plants, it is considered to be non-selective or broad spectrum. An herbicide is one type of pesticide. In common usage, however, the term is often used interchangeably with the words phytocide (plant killer) and silvicide (tree killer).
Honeydew - A sticky substance secreted by aphids and several other sucking insects.
Hormone - A chemical agent that controls various physiological processes within an organism: for example, adrenaline stimulates the heart, auxins and cytokinins in plants stimulate cell proliferation and growth.
Humic acid - A dark brown humic substance that is soluble in water only at pH values greater than 2. Humic acid is a long chain molecule, which slows uptake in hydroponic solutions; however, humic acid works very well in soil-based systems.
Humidity - The moisture content of air. Relative humidity is the ratio of the amount of water vapor actually present in the air to the greatest amount possible at the same temperature.
Humus - The well-decomposed, relatively stable portion of the partly or wholly decayed organic matter in a soil, which provides nutrients and helps the soil retain moisture.
Hybrid - The progeny that results from the mating or crossing of two different species or organisms. In plants, hybrids often display characteristics that are more favorable than those of their parents.
Hybrid vigor - Hybrid vigor is a condition where the progeny of a cross (the hybrid) displays greater height, yield, resistance, etc. than the parents, or the superiority of the heterozygote (hybrid) with respect to the parents.
Hydrogen Peroxide (H2O2) - An unstable, colorless, heavy liquid used as a bleach in industry and as an antiseptic in households. It is used as an oxidizing agent in pools and spas. H2O2 may also be used to de-chlorinate a swimming pool or spa water.
Hydrolysis - A chemical reaction in which a compound reacts with water, resulting in its decomposition or alteration.
IAA - The most common naturally occurring auxin. Promotes growth in excised plant organs, induces adventitious roots, inhibits axillary bud growth, and regulates gravitropism.
IBA - A substance that is closely related in structure and function to a natural growth regulator found in plants. Indole-3-butyric acid is used on many crops and ornamentals to promote growth and development of roots, flowers and fruits, and to increase crop yields. Growers find it more effective and efficient than its natural counterpart because plants cannot break it down as quickly. No harm to humans or the environment is expected to result from use of indole-3-butyric acid.
Infection - The introduction or entry of a pathogenic microorganism into a susceptible host resulting in the presence of the microorganism within the body of the host whether or not this causes detectable pathologic effects.
Inflorescence - A floral axis that contains many individual flowers in a specific arrangement; also a flower cluster.
Inhibit - To hinder or to prevent.
Inoculate - To treat, usually seeds, with microorganisms to create a favorable response. Most often refers to the treatment of legume seeds with Rhizobium to stimulate dinitrogen fixation but also refers to the introduction of microbial cultures into sterile growth medium.
Insecticidal soap - An organic mixture that is effective in destroying soft-bodied insects such as: aphids, mealy bugs, spider mites, thrips, soft brown scale, psyllids, rose or pear slugs, sawfly larvae, earwigs, lace bugs, whiteflies. It works by breaking down the coating that helps the adult or young insect retain moisture in its body. Once this coating is disrupted, the insect dehydrates and dies. Many commercial mixtures are readily available - a common brand name is "Safer".
Insects - a variety of insects attack plants. These include aphids, caterpillars, cutworms, fungus gnats, leaf miners, nematodes, spider mites, thrips, and whiteflies.
Internode - The region of a stem between two nodes, where there is no branching of the vascular tissue.
Interplanting - (See Companion planting)
Interveinal - In between the veins of the leaf, as in interveinal chlorosis.
Ion - An ion is an atom or group of atoms that carries a positive or negative electrical charge because of having lost or gained one or more electrons.
Iron - One of the seven micronutrients essential for plant growth. It is essential for chlorophyll synthesis, which is why an iron deficiency results in chlorosis.
Irrigation - The controlled application of water for cultural purposes through man-made systems to supply water requirements not satisfied by rainfall.
Juvenile - Young.
Kreb cycle - (See Dark reactions)
Ladybug - Small, round, bright-colored, and spotted beetle that usually feeds on aphids and other insect pests.
L-amino acids - (see amino acids)
Lamp - (See Bulb)
Leach - To remove soluble or other constituents from a medium by the action of a percolating liquid, as in leaching salts from the soil by the application of water.
Leaf miner - Any of various small moths or dipterous flies whose larvae burrow into and feed on leaf tissue, especially of the family Gracilariidae.
Leaf mold. See Cladosporium.
Light reaction - The first stage of photosynthesis during which energy from light is used for the production of ATP.
Limestone - A rock composed of more than 50% calcium carbonate [CaCO3]. Dolomite is a variant that is rich in magnesium.
Lipids - Oily substances that include, fats, oils and waxes.
Long day plants - Long-day plants are those that require a long period of exposure to light each day in order to produce flowers, this period is usually 14+ hours.
Lumens - Unit of measure for total light output. The amount of light falling on a surface of one square foot.
Lux - A measurement of light. 1 lux equals the illumination produce by 1 lumen falling on a surface measuring 1 square meter.
Macroelement - Nutrients that are needed in greater amounts than any other plant nutrients. Example: Nitrogen, Phosphorus, and Potassium are the three Macroelements.
Magnesium - One of the two secondary macronutrients essential for plant growth. Most soils have sufficient supplies of magnesium to insure healthy plants, but sandy soils may be deficient. In addition to activating enzymes that form oils, starch, and fats, magnesium also is a component of the chlorophyll molecule. Symptoms of magnesium deficiency appear first on older growth in the form of interveinal chlorosis. New growth is reduced or stunted.
Manganese - One of the seven micronutrients essential for plant growth. Manganese activates some important enzymes involved in chlorophyll formation. Manganese deficient plants will develop chlorosis between the veins of its leaves. The availability of manganese is partially dependent on soil pH.
Maturation - The act or process of becoming fully-grown.
Mealy bug - Scale-like plant-eating insect coated with a powdery waxy secretion; destructive especially of fruit trees
Meristem - A small group of cells that retain the capacity for rapid cell division (growth). The main meristematic areas within the plant are the apical meristems of the terminal and lateral shoots, the vascular cambium, the root apex, and the marginal meristems (active during the growth of leaves).
Metal Halide - Metal halide lights are a type of light bulb which burns very white and very bright. They require a special fixture and ballast. They are the closest thing we have to artificial sunlight, and are typically used on reefs and planted tanks. They are very efficient in terms of lumens/watt. Do not confuse these with halogen bulbs, which have a very yellow light not appropriate for plant use.
Microelements - A group of chemical elements that are needed in minute quantities for the proper growth, development, and physiology of an organism. Examples include: Iron, Manganese, Boron, Molybdenum, Copper, Zinc, and Sulfur.
Micronutrients - the minor minerals that are used by plants in small amounts, consisting of boron (B), copper (Cu), cobalt (Co), iron (Fe), manganese (Mn), molybdenum (Mo), and zinc (Zn).
Mineral deficiency - when a plant is not receiving a required nutrient--at all or in an insufficient amount--a disorder will result.
Mist system - A system of water delivery that can serve several functions: Propagation of cuttings, and evaporative cooling.
Mites - Mites are relatives to the spider, but are very small and often microscopic. They can be yellow, red, or green. Like their relatives, mites can spin minute webs under leaves and in joints between stems. Before you ever see the mites, you'll probably see tiny yellow spots on leaves. To confirm the presence of mites, tap leaves over a white surface where the tiny spiders will be more visible. Mites are frequently a pest of drought stressed plants and can usually be controlled by keeping plants well watered and by hosing off those that are heavily infected. Insecticidal soaps can also be used.
Mold - A common name for fungi that grow in a filamentous fashion and reproduce by means of spores; all molds are fungi, but not all fungi are considered 'molds'
Molybdenum - One of seven micronutrients essential to plant health. Molybdenum is used by plants to reduce nitrates into usable forms. Some plants use it for nitrogen fixation, thus it may need to be added to some soils before seeding legumes.
Monocot - One of two main divisions of flowering plants (the other being dicots), characterized by having a single cotyledon (seed leaf); examples include grasses, orchids, bamboos, and palms.
Monoecious - varieties or species with separate male and female flowers on each plant.
Mother plant - In hybridization, the plant or species that is pollinated in order to create hybrid seed. Also used to describe the original plant after cuttings are taken, or it sends out runners which root and establish as daughter plants. The term is frequently applied to strawberry growing where mother plants should be removed every few years to maintain health and berry production.
Mulch - A natural or artificial layer of plant residue or other material on the soil surface. Mulch reduces erosion, conserves soil moisture, inhibits weed growth, and can provide the soil with organic matter as it breaks down. Mulch till prepares the soil so as to leave plant residues (or other mulching materials) on or near the surface.
Mutation - A change in the genetic material, i.e. DNA.
Mycorrhizae - Mutualistic association of a fungus with the root of higher plant. In this relationship, the fungus helps the plant in extracting certain nutrients from the soil. In exchange, the fungus is provided with a habitat and nutrition in the form of carbohydrates.
Napthalene Acetic Acid - Napthalene Acetic Acid can significantly increase the number, length and dry weight of root hairs, small roots and large roots.
Necrosis - Referring to the death of tissue within a certain area.
Neem oil - Neem oil is an extract derived from the neem tree and contains a wide variety of compounds. The collective action is that of insect repellent, feeding inhibitor, egg-laying deterrent, growth retardant, sterilant and toxin. It affects some 170 insect species in several orders, which includes some beneficials.
Neem is relatively non-toxic to mammals.
Nematode - Nematodes are invertebrates comprising the parasitic roundworms. A smooth, narrow, cylindrical, non-segmented body tapered at both ends characterizes them. They shed their tough outer cuticle four times during life to allow growth. The microscopic free-living forms are found in all parts of the world, where they play an important role in the destruction and recycling of organic matter. The parasitic nematodes are much larger and some of them can cause serious diseases in man.
Nutrient Film Technique - Hydroponic technique used to grow plants. NFT delivers a film of water or nutrient solution down a trough or tray where the plants are located, either continuously or through on-off cycles (e.g., on 8 minutes and off 7 minutes).
Nitrogen - One of the three macronutrients essential for plant growth. Nitrogen is a major component of plants; it is a building block of amino acids, proteins, and nucleic acids (genetic material), chlorophyll, and enzymes. Though nitrogen is in air, it is only available to plants once soil microorganisms have fixed it. Nitrogen deficiency is not uncommon; it is readily apparent as chlorosis and stunted growth. Deficiencies can be remedied by adding manure, compost, urea, seed meal, or blood meal. Leguminous cover crops will also supply nitrogen.
Node - The point on a trunk or stem where a branch or leaf is attached.
Nutrient solution - An aqueous solution consisting of a set volume of water and mineral nutrients that are applied to the root zone in hydroponics. Minerals dissolved in water that are used to feed hydroponically grown plants.
Organic - Embellishes a commitment to an agriculture method which strives for a balance with nature, using methods and materials that are of low impact to the environment. Organic Production Systems include: Replenish and maintain soil fertility; Eliminate the use of toxic and persistent chemical pesticides and fertilizers; Build a biologically diverse agriculture. Organic foods are minimally processed to maintain the integrity of the food without artificial ingredients, preservatives or irradiation.
Osmosis - the flow or diffusion that takes place through a semipermeable membrane typically separating a solvent and a solution that strives to bring about a condition of equilibrium.
Ovary - In flowering plants, the part of the flower which encloses the ovules. When the ovary matures, it becomes the fruit.
Oxygen - A colorless, odorless, tasteless gas. Most life on earth requires oxygen to live. Animals breathe oxygen out of the air or water. Plants also need oxygen, even though they produce oxygen by photosynthesis.
Ozone - A gas, O3, which is very reactive. It is used as a sterilizing agent to kill bacteria and small organisms in the water. It is usually produced by an ozone generator. It is important not to use too much ozone, as excess ozone can harm people and other creatures.
PAR - Is the light in the whole wavelength band from 400 nm (deep violet) to 700 nm (dark red) used by plants in photosynthesis; however, small portions of the wavelength are not used by plants. Example: Plants do not use green wavelengths.
Parthenocarpy - Process in which an unfertilized egg develops into a new individual; common among insects, some plants, and some other arthropods. Example: Seedless watermelons, grapes, and bananas.
Parts per million - a ratio figure that represents the amount of one substance that is in one million parts of another substance; commonly used to describe the relative concentrations of nutrient solutions.
Pathogen - Any disease-producing agent (especially a virus or bacterium or other microorganism).
Perennial - Plant that lives for three or more years, producing leaves and stems each year from rootstock, crown buds, or branches.
Perlite - A lightweight medium made from volcanic glass that has been heated to 1,600 °F, useful in opening cavities to allow water and air to reach the roots; often used in potting soils.
Pest - Any species, strain or biotype of plant, animal or pathogenic agent injurious to plants or other organisms and/or their products.
Pesticide - A chemical compound used to kill specific pests (plant or animal). Insecticides control insects; herbicides control plants.
Petiole - The "stalk" attaching the leaf to the stem.
pH - Refers to the “percent of hydrogen" ions in a volume of water. Pure water contains an equal amount of hydrogen and hydroxide ions; therefore they cancel each other out. Acidic water (pH < 7) has a higher number of hydrogen relative to hydroxide, and vice versa for basic water. Individual species of plants prefer different pH ranges for optimal growth and development.
Phloem - The specialized vascular plant tissue used for the transportation of dissolved sugars and other organic solutes within a plant.
Phosphorus - A primary plant macronutrient, usually found in slow-leaching soil forms, that is a main component of nucleic acids, including energy-transmitting ATP, as well as phosphoproteins and phospholipids.
Photoperiod - The relationship between the length of light and dark in a 24–hour period.
Photosynthesis - The manufacture by plants of carbohydrates and oxygen from carbon dioxide and water in the presence of chlorophyll with sunlight as the energy source. Oxygen and water vapor are released in the process. Photosynthesis is dependent on favorable temperature and moisture conditions as well as on the atmospheric carbon dioxide concentration. Increased levels of carbon dioxide can increase net photosynthesis in many plants.
Phytophthora - Destructive parasitic fungi causing brown rot in plants.
Pistil - The central organ of a flower containing the ovules. The female part of a flower.
Pollen - The word pollen is derived from the Latin word meaning fine flour or dust. Pollen is a collective noun that is treated as singular. A single individual is a pollen grain. A pollen grain is a microscopic plant that carries the male genome, which is one-half the genetic complement of the parent plant. The pollen grain produces the sperm that fertilizes the ovum, or female genetic complement, of the plant. The fertilized ovum develops into a seed.
Pollination - Process of transferring the pollen from its place of production to the place where the egg cell is produced. This may be accomplished by the use of wind, water, insects, birds, bats, or other means. Pollination is usually followed by fertilization, in which sperm are released from the pollen grain to unite with the egg cell.
Pollination - the transfer of pollen from the male part of a flower (stamen) to the female part of a flower (the style and stigma).
Potassium - One of the three macronutrients essential for plant growth. Potassium contributes to protein synthesis and the operation of the stomata. Potassium aids in disease resistance, as well as seed and root development. If a plant is potassium deficient, the plant will express an overall weakness, especially in its stem, while the leaf margin will yellow. To correct potassium deficiencies in soil, apply soil amendments such as greensand, granite dust, or manure.
Powdery mildew - Powdery Mildew is a fungus that appears as a white fuzzy coating on the upper leaves. Foliage will eventually wilt, brown, and drop. If detected early, it can be eliminated by spraying with a solution of 1 tbsp. baking soda, and 1 tsp. Vegetable oil to 1 gallon of water. Neem oil also works very well.
Praying Mantis - Is a kind of insect, of the family Mantidae (order Mantodea), named for their "prayer-like" stance. (The word mantis in Greek means prophet). There are approximately 2,000 species worldwide; most are tropical or subtropical. The most common species is Mantis religiosa. Mantids are notable for their large size and nimble reflexes. Their diet, which consists exclusively of living insects, includes flies and aphids, which are caught and held securely with the grasping forelegs. Mantids make use of protective coloration to blend in with the foliage, both to avoid predators themselves, and to better help snare their victims.
Precipitation - A process in which positive and negative ions combine to form a salt that precipitates out of the solution as a solid.
Pyrethrin - Chrysanthemum cinerariaefolium, (Family Asteraceae), is a perennial African plant with a daisy-like appearance and white, pink or red flowers. The same species is also known as Pyrethrum roseum, Chrysanthemum coccineum, Tanacetum coccineum, or simply, the Painted Daisy. The plant is economically important as a natural source of insecticide. The flowers are pulverized and the active components, a group of esters oleoresins called pyrethrins (C21H28O3, or C22H28O5) contained in the seed cases, are extracted and sold in the form of an oleoresin. This is applied as a suspension in water or oil, or as a powder. Pyrethrins attack the nervous systems of all insects, and inhibit female mosquitoes from biting. When not present in amounts fatal to insects, they still appear to have a repellent effect. They are harmful to fish, but are far less toxic to mammals and birds than many synthetic insecticides and are non-persistent, being biodegradable and also breaking down easily on exposure to light. They are considered to be amongst the safest insecticides for use around food.
Pythium - Destructive root-parasitic fungi, which causes damping off disease in seedlings.
Raised bed - In raised bed gardening, the soil is formed in 3--4 foot (1.0--1.2m) wide beds, which can be of any length. The soil is about 0.5--1 foot (150--300cm) above the surrounding soil, sometimes enclosed by a frame generally made of wood or concrete blocks, and enriched with compost made from leaves and grass clippings.
Red light - (See Wavelength)
Reflector - A device used to redirect the light flow from a source by bouncing it off the surface.
Repellant - A substance serving or tending to repel an organism.
Reproduction - Process by which new organisms are generated. Reproduction may be sexual, involving the fusion of gametes, or asexual.
Resistance - The condition in which an organism can resist disease.
Respiration - A biochemical process by which living organisms take up oxygen from the environment and consume organic matter, releasing both carbon dioxide and heat. In plants, the organic matter in photosynthate produced during daylight hours.
Reverse osmosis - the process of removing minerals from water, which is forced by pressure through a differentially permeable membrane, filtering out the minerals; can happen when growers accidentally apply too strong of a nutrient to a plant's roots, leeching life out of the plant.
Rhizobium - Type of bacterium that has the capacity of both invading the roots of certain species of the Leguminosae and fixing atmospheric nitrogen, which is subsequently used by the host plant.
Rhizome - An underground portion of a stem, producing shoots on top and roots beneath; different from a root in that it has buds, nodes, and scaly leaves; rootstock.
Ripening - Coming to full development; becoming mature.
Rock phosphate - Is a naturally occurring mineral which has been ground to a fine dust. This dust is then granulated with natural binders, either lignosulfonate or molasses.
Root - The usually underground organ that lacks buds or leaves or nodes; absorbs water and mineral salts; usually it anchors the plant to the ground or growing medium.
Root hair - Thin hair like outgrowth of an epidermal cell just behind the tip; absorbs nutrients from the soil.
Runner - A very slender, wiry stem, as in the strawberry, that grows along the surface of the soil and propagates by producing roots and shoots at the node at the tip. Also known as a stolon.
Salinity - (1) The relative concentration of salts, usually sodium chloride, in a given amount of water. It is usually expressed in terms of the number of ppm of chloride. (2) A measure of the concentration of dissolved mineral substances in water
Salt - Any compound formed by combination of any negative ion (except hydroxide) with any positive ion (except hydrogen or hydronium); the precipitate produced as the result of neutralization of an acid with a base.
Sand - Sediment particles mainly or quartz, with a diameter of between 0.062 mm and 2 mm, generally classified as fine, medium, coarse or very coarse.
Saponin - Any of various plant glucosides that form soapy lathers when mixed and agitated with water; used in detergents, wetting agents, foaming agents, and emulsifiers.
Scarification - Abrasion of the seed coat that allows water and oxygen into the seed, thereby helping to improve germination in some species.
Short day plants - Plants taht form flowers only when day length is less than about 12 hours. Many spring and fall flowering plants are short day plants, including chrysanthemums, poinsettias and Christmas cactus. If these are exposed to more than 12 hours of light per day, bloom formation does not occur.
Silicon - A nonmetallic chemical element, number 14, which is a major component of many types of rocks and minerals on Earth; used to make glass, concrete, and semiconductors. Potassium silicate is a plant nutrient that fortifies plant walls for increased drought, insect, and heat stress.
Socket assembly - Threaded metal assembly where an HID lamp is attached to the lighting system.
Soil - Unconsolidated mineral and organic material that supports, or is capable of supporting, plants, and which has recognizable properties due to the integrated effect of climate and living matter acting upon parent material, as conditioned by relief over time.
Soilless - A plant medium that contains no soil, which may harbor weed seeds, and pathogens, but does contain soil alternatives like peat moss, ground pine bark, and perlite for drainage.
Sow - Place (seeds) in or on the ground for future growth.
Spider mite - (See Mites)
Spore - An asexual, usually single celled, reproductive body of organisms such as fungi, mosses or ferns; a microorganism, as a bacterium, in a resting or dormant state.
Stalk - on a male flower, the portion of the stamen that supports the anther.
Stamen - The part of the flower where the pollen is produced. Usually comprised of a filament and an anther. The male part of a flower.
Stamen - the basic part of the male flower that includes the stalk (or filament), anther, and pollen.
Sterilization - the act of rendering something free from living cells. In hydroponics it is essential that all materials (especially any growing medium) used are sterile to avoid contaminating the hydroponic system. Steam and chemical agents are often used in this process.
Stigma - the surface at the end of the pistil on a female flower where pollen lands and germinates.
Stock plant - (See Mother plant)
Stock solution - A nutrient solution that is typically 100 to 200 times more concentrated than a standard per gallon dose, which is then passed through a fertilizer injector to mix the solution with water for irrigating plants in production.
Stock tank - A 500-1000 gallon tank which holds the stock solution.
Stratification - A pregermination treatment to break dormancy in seed and to promote rapid, uniform germination. The seeds are exposed to moisture at a temperature just above the freezing point (1-5 deg. C) for a specified time.
Style - the part of a female flower that supports the stigma.
Succession planting - Planting smaller crops in one to two week intervals to prolong the harvest over a longer period of time.
Sulfur - A micronutrient for plants, usually found as the sulfate divalent anion in soil solution. Sulfur is a main component of a group of amino acids.
Switchable - A single ballast box that contains two HID ballast cores, one for Metal Halide and one for High Pressure Sodium. A single toggle switch allows the user to quickly, and easily “switch" from a Metal Halide light to a High Pressure Sodium light.
Taproot - A primary, sparsely branched root which may penetrate to considerable depth; a carrot).
Thrips - Thrips are very small insect pests that attack a number of different plants species.
Hydroponic gardening
