Hydroponic Index





Hydroponic Glossary

 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z





Uptake of nutrients from the soil by plant roots, or directly into the leaves from foliar sprays.

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


Supplying soil and roots with air or oxygen.

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

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

A method of growing that uses rockwool, net pots, vine clips, or other devices to support the plant while its roots grow in the air with a constant mist of nutrient solution. Growing plants in this method of oxygen infused into the nutrient solution allows roots to absorb nutrients faster and easier therefore providing rapid growth and fantastic yields.

Aeroponics is a form of hydroponics. The roots of the growing plants are suspended in the air, and they are misted by high pressure sprayers. The sprayers break the nutrient into small particles and saturate the roots. The levels of oxygen in the water are kept high by the constant circulation of the water. Experiments with aeroponics have shown that plants can grow up to 50% faster than in regular hydroponic systems.

Algal Bloom
Exaggerated algal growth due to oversupply of nutrients in the waterway.

The pollen-bearing part of the stamen.









Extremely small, one-celled organisims that don't have chlorophyll.

Bacterial soft rot
See Botrytis.

The electrical components that energize a high intensity bulb. (Typically a transformer or a capacitor)

Beneficial Insect
An insect that eats bad flower and vegetable eating insects.

The process of removing clay and other impurities from phosphate rock to enhance the phosphorus content of the rock.

Capable of being decomposed by biological agents, especially bacteria.

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


When a plant prematurely begins the development of a flowering stalk, and, subsequently, seed.,

Boron (B)
The function of this micronutrient is not well understood, but it is suspected that it might aid carbohydrate transport.

Any of various fungi of the genus Botrytis responsible for numerous diseases of fruits and vegetables; often referred to as bacterial soft rot or gray mold.

The ability of a substance to reduce shock and provide cushion against pH flucuations.

Buffer Solutions
Buffers are solutions that have constant pH values and the ability to resist changes in the pH level. They are used to calibrate the pH measurement system (electrode and meter) Buffers are available with a wide range of pH values, and they come in both premixed liquid form or as convenient dry powder capsules.

Leaf tips that turn dark from excess fertilizer and salt burn.





Calcium (CA)
Calcium is vital in all parts of plants to promote the translocation of carbohydrates, healthy cell wall structure, strong stems, membrane maintenance, and root structure development. Calcium is a macronutrient

Carbon Dioxide (CO2)
A colorless, odorless, tasteless gas in the air necessary for plant life. Occurs naturally in the atmosphere at .03%.

Capillary action
A phenomenon associated with surface tension and resulting in the elevation or depression of liquids in capillaries. This is similar to the manner in which plants seem to defy gravity when they transport liquid upwards from their roots.

Caton Exchange Capacity
A measure of soil's ability to hold positively charged nutrient ions for plant use.

Conductive factor (See Conductivity)

Combining nutrients in an atomic ring that is easy for plants to absorb.

Chlorine (Cl)
This micronutrient is essential for photosynthesis, where it acts as an enyzme activator during the production of oxygen from water.

Any of a group of related green pigments found in photosynthetic cells that converts light energy into ATP and other forms of energy needed for biochemical processes; it is found in green plants, brown and red algae, and certain aerobic and anaerobic bacteria.

The condition of a sick plant with yellowing leaves due to inadequate formation of chlorophyll. Chlorosis is caused by a nutrient deficieny, usually iron or nitrogen; nutrient deficiencies are themselves often caused by a pH that is out of the acceptable range.

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

Closed System
A hydroponic system, like nutrient film technique (NFT) systems, that recirculates the nutrient solution.

C/N Ratio
Carbon-to-nitrogen ratio in soil. Provides a measure of the quality and rate of decomposition of organic matter. The lower the ration, the quicker the organic matter will break down, and release nutrients in forms available for plant uptake.

Color Temperature
The relative color of light emitted by a lamp. An example is a piece of red hot iron emits a red glow which has a low color temperature. A piece of hite hot iron emits a glow with more blue light, which makes the color more white, and a higher color temperature. The unit of measure for color temperature is called "Kelvin" and is expressed in degrees Kelvin.

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

The scale used to measure the strength of nutrient solution. Pure water doesn't conduct any electricity but as you dissolve mineral salts in the water you increase Conductivity. More salts, stonger solution, higher Conductivity.

Copper (Cu)
This micronutrient is an internal catalyst and acts as an electon carrier, it is also believed to play a role in nitrogen fixation.

The transfer of pollen from an anther of the flower of one plant to a stigma of the flower of another plant.




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

A lack or shortage, especially of something essential to health; an insufficiency: a nutritional deficiency. When a plant's nutrient uptake is deficient it is evidenced by visual symptoms such as, but not limited to, changes in color, malformed leaves, and dying leaves.

The loss or removal of nitrogen or nitrogen compounds; specifically : reduction of nitrates or nitrites commonly by bacteria (as in soil) that usually results in the escape of nitrogen into the air. Often occurs in waterlogged soils.

Dioecious Of or relating to organisms, especially plants, having the male and female reproductive organs borne on separate individuals of the same species; sexually distinct.

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

Drip Aeration
A hydroponic method wherein air pressure from a small air pump is used to percolate nutrient solution out through a ring of feeder tubing which encircles the plant.

Drip System (Drip Emitter System) A very efficient watering system that employs a main hose with small water emitters. Water is metered out of the emitters, one drop at a time.

Dry Rot
See Fusarium





Ebb and flow
The term "Ebb and Flow" simply means a method of irrigation that completely floods the growing media root zone, then lets the water drain away from the root zone, back to the reservoir. It is also called the "Flood and Drain" method by some growers.
Electrical conductivity See Conductivity

Having waters rich in mineral and organic nutrients that promote a proliferation of plant life, especially algae, which reduces the dissolved oxygen content and often causes the extinction of other organisms




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.

Fertilizer Burn
Over fertilization: identified by leaves first turing yellow (burning) then curling.

Any of a large number of natural and synthetic materials, including manure and nitrogen, phosphorus, and potassium compounds, spread on or worked into soil to increase its capacity to support plant growth.

The stalk that bears the anther in a stamen. See Stalk

The process by which available plant nutrients become unavailable by reaction with components of the soil.

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


The amount of light that illuminates 1 square foot of surface area, one foot in distance from the candle.

A product that destroys or inhibits fungus.

Any of a major group (Fungi) of saprophytic and parasitic spore-producing organisms usually classified as plants that lack chlorophyll and include molds, rusts, mildews, smuts, mushrooms, and yeasts. Common fungal diseases that attack plants are "damping-off," Botrytis, and powdery mildew.

A form genus of fungi (family Tuberculariaceae) including important plant pathogens and several infectious agents that afflict plants, commonly referred to as dry rot or wilt


One of several brand names/varieties of clay aggregate medium (also known as LECA for light expanded clay aggregate). It is a lightweight, porous substrate with excellent aeration. Because it does not really wick water effectively, Geolite and other LECA mediums are favorites in ebb-and-flow and drip hydroponic systems.

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

Gray Mold
See Botrytis

Growing Medium
Materials occasionally used in hydroponic growing to support a plant's roots and, sometimes, to hold nutrient.

Hydrated calcium sulfate, used as a soil conditioner. It can be mined from natural sources or produced as a by-product when manufacturing phosphoric acid, if obtained in that manner it's known as phosphogypsum.





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

H.I.D. (High Intensity Discharge) Lights
Lights that produce very intense light using an electric arc with metallic vapor inside a quartz arc tupe surrounded by a glass outer bulb that prevents ultraviolet rays from being radiated. These horticultural lights produce 5-6 times as much light compared to incandescent lights of the same wattage and last 10-30 times as long. These durable systems have a life span of 15+ years.

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

Humidity (Relative)
The ratio of water vapor density (mass per unit volume) to the saturation water vapor density. Basically the ratio between the amount of moisture in the air and the amount of moisture the air could hold at that same temperature.

A brown or black organic substance consisting of partially or wholly decayed vegetable or animal matter that provides nutrients for plants and increases the ability of soil to retain water.

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

Hyrdrated Lime
Instantly soluble lime, used to raise or lower pH.

An instrument for measuring relative humidity in the atmosphere.

Hydrogen Peroxide (H2O2)
A clear sharp smelling substance very similar in appearance to water. Like water it is made up of Hydrogen and Oxygen, however H2O2 has an extra Pxygen atom in an unstable arrangement. It is this extra atom that gives H2O2 it's useful properties. Hydrogen is useful in hydroponics for pretreating water.

Cultivation of plants in nutrient solution rather than in soil.




Inbred (True Breed)
Offspring of plants of the same breed or ancestry

Chemically non-reactive; inert growing mediums make it easy to control the chemistry of the nutrient solution.

Inline Fans
Inline fans have the motor and blade inside a housing that's usually circular. They are useful for moving air from one room to another, or through walls, or ceilings to outside. They may be used with short lengths of ducting to control direction of air flow. These are the most commonly used fans for exhaust vents, at the top of the growing area. This draws out the hot, stale air. Inline fans have the advantage of being thin. They may be place directly into walls or ceilings. They may also be used to send air through short lengths of ducting.

There are several types of insects that attack plants. These include; aphids, caterpillars, cutworms, fungus gnats, leaf miners, nematodes, spider mites, thrips, and whiteflies.

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

Iron (Fe)
This micronutrient acts as a catalyst in the photosynthesis/respiration process, and is essential for the formation of sugars and starches. Iron also activates certain other enzymes.




 The protective outer bulb or envelope of lamp.




A unit of measurement for expressing the heat or light given off by an object. At zero degrees Kelvin no molecules would be moving and no heat or light given off. Natural sunlight is 5500 degrees Kelvin. Light that has less blue will have a lower Kelvin temperature.

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




Open to change; adaptable, describes a soil nutrient which may become available for plant uptake.

Beneficial insects that prey on aphids

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

Washing of nutrients through the soil to a depth beyond the root zone of plants.

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

Leaf Mold
See Cladosporium

Small immature leaf

Abnormally tall internode space, with sparse foliage. Legginess of a plant is usually caused by a lack of blue light or CO2. It can also be caused by too much nitrogen.

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 across or in a circle around the ceiling of a garden room to provide more even distribution of light.

Used in the form of dolomite or hydrated lime to raise and stabilize soil pH.

Litmus Paper
Chemically sensitive paper used for testing pH. The paper is chemically treated in such a way that when dipped into a water sample it will change color to indicate the pH level.

Organic soil mixture of crumbly clay, silt, and sand.

The amount of light emitted by a candle at a distance of 1 foot from the candle.

Lumens per Watt
The lumen output of a lamp, divided by the input wattage.




The primary nutrients consisting of nitrogen (N), phosphorus (P), potassium (K), and sulfur (S) or the secondary nutrients magnesium (Mg) and calcium (Ca).

Manganese (Mn)
This micronutrient activates one ore more enzymes in fatty acid synthesis; it also activates the enzymes resonsible for DNA and RNA production. Closely associated with copper and zinc, manganese also participates directly in the photosynthetic creation of oxygen from water.

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

Also referred to Trace Elements. They are the minor minerals used in small amounts by plants consisting of boron (B), copper (Cu), cobalt (Co), iron (Fe), manganese (Mn), molybdenum (Mo), and zinc (Zn).

Mineral Deficiency
Lack of a mineral micronutrient that is essential for normal nutrition or metabolism. When a plant is not receiving a required nutrient, either all or an insufficient amount, a disorder will result.

The process carried out by soil micro-organisims whereby nutrients are released in an inorganic form from the decomposition of organic material.

Mobile Nutrients
The nutrients that move freely with soil moisture, or can be moved within the plant from older tissues. Some nutrients can immobile in soils and mobile in plants, and vice versa.

Molybdenum (Mo)
Micronutrient essential for nitrogen fixation and nitrate reduction.

Varieties or species with seperate male and female flowers on each plant.

A protective covering, usually of organiz matter such as leaves, straw, or peat, placed around plants to prevent the evaporation of moisture, the freezing of roots, and the growth of weeds.

A metallic film that is similar to a paper thin mirror that is either taped or tacked to the walls in a growing area.




The unit of length equal to one billionth of a meter. It is used to measure the spectrum of light colors. Blue light has a shorter wavelength than red light

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

Nitrogen (N)
Nitrogen is used in various forms to promote rapid vegetative growth, leaf, flower, fruit, and seed development, and chlorophyll development; and to increase the protein content in plants.

The process by which soil organisms use oxygen to convert ammonium ions to nitrate ions.

Nitrogen (N)
Nitrogen is used in various forms to promote rapid vegetative growth, leaf, flower, fruit, and seed development, and chlorophyll development; and to increase the protein content in all plants.

A soil nutrient which is tied up in the soil and unavailable for plant uptake.

Nutrient Film Technique (NFT)
A hydroponic method in which nutrient is fed into grow tubes or trays in a thing film where roots draw it up. This "nutrient film" allows the roots to have constant contact with the nutrient and the air layer above at the same time.

Nutrient Solution
The mixture of water and water-soluble nutrients which is provided to the plants for nourishment in a hydroponic system.

Elements such as nitrogen and iron that are needed for plant growth and health.

Nutrients, Secondary
The elements other than N, P, and K which are considered nearly as important as N, P, and K but are not considered micronutrients. Calcium (Ca), magnesium (Mg), and sulphur (S) are the elements usually referred to by this term.




Oscillating Fans
These are the same type of fans used for room air movement. There are special wall mount horticultural oscillating fans. These are best for sending waves of fresh Carbon Dioxide charged air to the plant leaves. The oscilliation feature sends new air across the complete growing area. The important thins is to keep bringing fresh air in contact with the leaves of the plants.


The diffusion of fluid through a semipermeable membrane seperating a solvent and a solution to bring about a condition of equilibrium.




Parts Per Million (PPM)
The ratio figure that represents the amount of one substance that is in one million parts of another substance; often used to describe the relative concentrations of nutrient solutions.

Photosynthetically Active Radiation, the part of the sunlight spectrum that plants use

A hydroponic system without a pump. The plants take up nutrients through a fibrous wick from the pot to the nutrient solution.

A white, grasslike volcanic mineral, about one-tenth the weight of sand, that is useful as a medium for rooting cuttings but lacks any nutrients.

The pH scale is a way to measure the Acid or Akaline qualities of water. The offical definition of pH is: a unit of measure which describes the degree of acidity, or alkalinity of a solution. It is measured on a scale of 0-14. The term pH is dervied from "p" the mathematical symbol of the negative logarithm, and "H", the chemical symbol of Hydrogen. The folrmal definition of pH is the negative logarithm of the Hydrogen ion activity {pH=-log[H=]}. pH expresses the degree of an activity of an acid or base in terms of hydrogen ion activity. In general,plants grow best in a pH range of 6 to 6.8; 6.3 is considered ideal. If the pH is not within the acceptable range, nutrients may not be absorbed to maxium capacity.

The duration of an organism's daily exposure to light, considered especially with regard to the effect of the exposure on growth and development.

Phosphorus (P)
Phosphorus promotes and stimulates early growth, blooming, and root growth. It hastens maturity and seed growth, and contributes to the general hardiness of plants. Phosphorus is a macronutrient.

The process in green plants and certain other organisms by which carbohydrates are synthesized from carbon dioxide and water using light as an energy source. Most forms of photosynthesis release oxygen as a byproduct.

The female, ovule-bearing organ of a flower, including the stigma, style, and ovary.

The fine powderlike material, consisting of pollen grains, that is produced by the anthers of seed plants.

The carrying of pollen grains to the female sex cells for fertilization.

Potassium (K)

Potassium promotes disease resistance and good development of carbohydrates, starches, and sugars. It also increases fruit production. Potassium is a macronutrient.

1.Sexual: To produce seed by breeding different male and female flowers. 2. Asexual: To produce plantlets (also known as clones) by taking cuttings.

Natural insecticide made from the blossoms of various chrysanthemums.




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

Reverse Osmosis
The process of removing minerals from water by pushing a solution through a filter that traps the solute on one side and allows the pure solvent to be obtained from the other side.

Inert, soilless growing medium consisting of woven, thin strand-like fibers made from molten volcanic rock and limestone, which is heated to over 2900 degrees farenheit, extruded, and formed into slabs, cubes, and blocks.




Sailine Soil
Soil which affects plant growth due to high levels of salinity. Normally associated with sodium choloride.

Salt Index
The measure of the ratio of change in osmotic pressure caused by different fertilizers. A fertilizer with a high salt index may cause damage to when applied near or directly to seeds.

Secondary Nutrients
Calcium (Ca) and magnesium are considered to be the secondary nutrients.

To apply granular fertilizer to the soil alongside a plant or row of plants during the growing season to stimulate them.

Sodic soil
Soil where the structure has been affected by high concentrations of exchangable sodium.

Soil Fertility
The status of soil in regards to the amount and availability of essential nutrients.

Split Application
Splitting the seasonal fertilizer requirement into a number of smaller applications. This technique is commonly used for nitrogen and potassium, which are subject to loss through leaching.

A stem or similar structure that supports a plant part such as a flower, flower cluster, or leaf. On a male flower it is the portion of the stamen that supports the anther.

The pollen-producing organ of a flower, usually consisting of a filament and an anther.

The state or condition of being free from microorganisms. In hydroponics it is essential that all materials being used are sterile to avoid contamination of the hydroponic system.

The receptive apex of the pistil of a flowe, on which pollen is deposited at in pollination.

The usually slender part of a pistil, situated between the ovary and the stigma.

Used in reference to a disease within the plant tissue, not intiated from the external cells. Also refers to materials and compounds which are taken up or absorbed by the plant and designed to fight disease (e.g. systemic fungicide).






Tap Root
The main or primary root that grows from the seed; lateral roots will branch off the tap root.

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

Give off water vapor and by products via stomata and carbon dioxide intake at the leaves.

Frame of small boards (lattice) that trains or supports plants.

Uniform broadcast application of fertilizer to the soil surface after a crop or pasture has become established.

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






Light with very short wave lengths, out of the visible spectrum past the blue-violet




VAM (Vesicular sbuscular mycorrhiza)
A soil fungus that attacks the roots of some plants and assists in the uptake of phosphorus and other immobile nutrients

Mica which has been processed and expanded by heat. Vermiculite has excellent water retention qualities and is a good soil amendment and medium for rooting cuttings

The process by which certain soluble soil nutrients are changed from solid or aqueous forms to gaseous forms and are lost from the soil to the atmosphere.




Watts per Square Foot
The wattage of a lamp, divided by the size of the coverage area.

Part of 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.

Any plant disease characterized by drooping and shriveling; usually caused by parasites attacking the roots.




Zinc (Zn)
Like copper and manganese, zinc is linked to chlorophyll synthesis.



Strawberries need one year or longer to mature from seed. Try and find a cutting to propagate. Also try to get a self pollinating variety. They require a high level of light for 16 - 18 hours per day. Any standard hydroponic nutrient should be sufficient.

Strawberries grow well hydroponicaly, I tried it myself with very good results! I used Rockwool as a growing medium and a flood and drain system.

Nutrients   http://www.gchydro.com/art_Mantra.asp  Some mineral-based nutrients are slightly better than others depending on the source of the nutrients.



Flushing Program   http://www.hydroponics.com.au/back_issues/issue37.html  "Unless you keep a good regular program of flushing, there is a build-up of salts, not just of sodium and chloride, but potassium and nitrogen as well," observed Keith.

Beneficial Bacteria

In the early days, Keith and Vivian thoroughly cleaned the lettuce system between crops; anything they could do to minimise the transfer of disease was no effort. But all that stopped 3 years ago when they started using Amnite 100, a blend of 23 beneficial bacterial and fungal organisms.
Beneficial bacterial and fungal organisms are marketed in Australia under different names including Amnite 100, Get-Back-Teria, Ag-Bact L, Organosol and OGP, among others. Initially, it was used as a foliar spray, and put through the lettuce root zone, but Keith found the foliar spray caused too much bacteria on the leaves of the lettuce.
He now restricts the friendly micro-organism to the root zone. For the flower crop, Keith uses the micro-organisms as a foliar spray, rather than through the roots where they tend to block the drippers.
"One very clear problem that it cleared up amongst the flowers is botritus, and whenever I don't have enough bacteria, the botritus returns," commented Keith. According to Keith, the 'friendlies' make the nutrients in the solution more available to plants, however he warns that the micro-organisms will not work properly outside of certain temperature parameters, or if there's not enough oxygen in the system.
"I have found it definitely works for me, and we've found certain ways to apply it which helps it to work better, added Keith.

Gravel Filtration System

The lettuce system incorporates a fast-flowing gravel filtration system. Using a 1000 litre fibreglass tank, the filter consists of a series of different size gravels, from fine through to coarse grade. An inlet pipe extends across the diameter of the gravel filter, its underside peppered with large holes to disperse the nutrient solution across the breadth of the gravel filter, at a rate of 3 litres per second. The inlet pipe is covered with a 'pantyhose' stocking to act as a fine filter. The filter system is used to distribute the beneficial micro-organisms throughout the system.
"The gravel filter is an excellent area for the bacteria to exist," Keith explains, "and I feel
I'm getting the same type of result as the sand filtration system (Practical Hydroponics & Greenhouses - September/October 1995 - Issue #24), but at a much faster rate."
Testimony to the health of the biofilter is evidenced by the colony of worms that live within the gravel.
"People say that inorganic fertilisers are not in 'sync' with normal biosystems, but to find worms in the gravel filter indicates to me that it is a very healthy system," commented Keith.


Although there has been little scientific work done to support the claims of products such as Amnite 100, there is a wealth of anecdotal evidence to suggest these products deserve closer scrutiny.
The symbiotic relationship between plant root systems and beneficial bacteria and fungi is widely recognised by many horticulture growers. It is now understood that there are extensive interrelationships between micro-organisms and plant roots. Some examples include seed innoculants which are used to sow legumes to provide nitrogen fixing bacteria for their roots; the use of beneficial fungi like actinomycetes spp, which are used as an adjuvant to fertilisers applied to fields; and vescular arbuscular mycorrihizae (VAM), which plays a critical role in helping plant roots extract nutrients from depleted soils.
It is known that crops like lettuce, grown in recirculating NFT systems, eventually accumulate large populations of pathogens such as Fusarium, Pythium spp and Verticillium spp. They cause destruction of roots and leaves, leading to plant death. In some horticultural applications, treatment often involves the use of agricultural surfactants, which are used to suppress the development/reproduction of such pathogens. However, surfacants are not registered in New South Wales for use in hydroponic nutrient solutions, with the exception of Agral 500.
Surfactants mimic the hormone oestrogen. When they get into the aqueous environment, they contaminate marine and riverine animal species causing males to lose their ability to produce testosterone, thereby having a feminising effect. This problem has been clearly demonstrated in the Florida Everglades where alligators are failing to reproduce.
Medical scientists know that our intestines are full of millions of bacteria, which are responsible for many of the reactions that occur during digestion. They assist us in assimilating the nutrients in our food. It is now recognised that
as we age, it is harder to maintain the population of friendlies in our gut. A depletion of beneficial bacteria leads to replacement and colonisation by harmful bacteria and fungi. An example is candida albicans, a harmful fungus that lives in the gut, producing harmful toxins that circulate in the bloodstream. This is why we are encouraged to eat yogurt daily, to replenish the friendly bacteria and maintain the balance.
Much work still needs to be done to fully understand the complex interrelationships between friendly micro-organisms and plants. Although controlled scientific experiments using products such as Amnite 100 have so far proved inclonclusive, strong anecdotal evidence suggests that these organisms seem to play an important role in the control and prevention of plant disease in hydroponic applications.

Baking Power for Mildew and Fungal Diseases –Abstract http://attra.ncat.org/attra-pub/bakingsoda.html

There has been considerable interest in the use of baking soda (sodium bicarbonate, NaHCO3) and potassium bicarbonate (KHCO3) to control powdery mildew and other fungal diseases of plants. This publication provides a brief survey of observations, research, and recommendations on the use of bicarbonates in horticulture. 

The use of baking soda as a fungicide is not a new idea. In Alfred C. Hottes' A Little Book of Climbing Plants, published in 1933 by the A.T. De La Mare Co. of New York, mention is made of using one ounce of baking soda per gallon of water to control powdery mildew (PM) on climbing roses. The author credits the idea to a Russian plant pathologist, A. de Yaczenski.(1)

In the August, 1985 issue of Organic Gardening magazine, a short article by Warren Shultz entitled "Recipe for Resistance" reports that researchers in Japan obtained effective control of PM on cucumbers, eggplants, and strawberries. They suggested weekly sprays of ¼ ounce baking soda per gallon of water.(2)

An article in the June, 1990 issue of Greenhouse Manager magazine summarizes the results of three years of testing baking soda as a fungicide for roses. Cornell University researcher Dr. R. Kenneth Horst observed suppression of PM and blackspot—both major problems for New York rose growers. Roses were sprayed every 3 to 4 days with a water solution of baking soda and insecticidal soap. The latter was included for its surfactant qualities. (Surfactants are chemical agents that alter the surface properties of a liquid.) The soap improved the effectiveness of the bicarbonate by making it stick to, and spread evenly over, the leaf surface. Further experimentation proved that the insecticidal soap itself was not responsible for suppressing the diseases. While no specific concentration of baking soda is indicated as being most effective in PM suppression, the article states that a 0.5% solution was most effective in preventing blackspot.(3)

Some of the work at Cornell has focused on controlling fungal diseases on cucurbits.(4) A single spray application (to runoff) of 0.5% (wt./vol. of water) baking soda, plus 0.5% (vol./vol. of water) SunSpray UFP® horticultural oil almost completely inhibited PM on heavily infected pumpkin foliage. Baking soda without spray oil was ineffective, and a 2% (wt./vol. of water) solution of baking soda damaged the leaves. Baking soda/oil sprays also provided good control of urocladium leaf spot in cucumber, alternaria leaf blight in muskmelon, and gummy stem blight in muskmelon.(5) Other diseases against which baking soda may prove effective include anthracnose in cucurbits (6); rust, dollar spot, and pythium blight in turf; late blight in potato; rust in wheat; and diseases affecting peanuts, banana, and alfalfa.(7)

Researchers in Israel reported the successful use of baking soda and SunSpray oil in controlling PM on euonymus.(8) In this research a 2% baking soda and 1% oil solution proved most effective.(9)

On-farm observations on melon acreage in Virginia resulted in one farm operation switching from synthetic fungicides to a baking soda/oil spray. These growers incorporated a liquid fertilizer into the mix.(10)

Research in Germany evaluated baking soda as a control for PM on `Bacchus' grapes. Three spray applications were made, beginning when symptoms first appeared. Good control was achieved with no loss of grape quality. The optimum concentration was a 1% solution.(11)

An article in the February, 1996 issue of GrowerTalks magazine follows up on the continuing research at Cornell. Testing with a variety of bicarbonates revealed that selecting the correct bicarbonate for a particular disease is important. Dr. Horst's research team found that ammonium bicarbonate had the strongest effect on some diseases, while potassium and sodium bicarbonates worked best against others. Potassium bicarbonate provided the best control of PM. "Sodium bicarbonate is okay, but it's not as good," Horst is quoted as saying. "And ammonium bicarbonate doesn't do the job on powdery mildew." He points out that while conventional chemical controls for PM are preventatives only, bicarbonates can eliminate the disease after it has already appeared on certain crops—he mentions roses and an unspecified ornamental—provided the infection is not severe. The only plant damage associated with bicarbonates applied in the trials was foliar burning when application rates exceeded recommended concentrations. Testing established that sodium bicarbonate does not increase the levels of sodium in plant tissues, soil, or runoff water. While their precise mode of action against fungi is not understood, Horst states that bicarbonates seem to damage the cell wall membrane in PM spores. He also believes pH to be a factor in bicarbonate effectiveness. In any case, bicarbonates are contact fungicides, and kill PM within minutes.(7)

The Federal EPA ruled (as of December, 1996) that sodium and potassium bicarbonates are exempt from residue tolerances.(12) This action served to facilitate the development and release of commercial bicarbonate products for horticultural use. It also lent weight to the belief that these materials are largely innocuous from a food safety perspective.

Connecticut researchers evaluated the effects of a spray solution containing 1% each of baking soda and horticultural oil on PM infection in zucchini, pumpkin, and cantaloupe. Four applications were made and disease suppression was definitely observed, accompanied by reduced insect pest damage. These researchers maintain that the treatment is preventative—not curative; that it is only necessary in years where early outbreaks may threaten yields; and that spraying should accompany proper nutrition and water management.(13)

In 1998, Church & Dwight Co. (14)—the manufacturer of Arm & Hammer™ baking soda—received EPA registration for Armicarb 100®, a potassium bicarbonate formulation, for use against PM, downy mildew, botrytis, and alternaria leaf-spot.(15) This product is the direct result of Dr. Horst's research at Cornell, which was funded by Church & Dwight. Armicarb 100 is now available from Helena Chemical Company.(16) A similar product is sold under the name FirstStep® by the W.A. Cleary Chemical Co.(17)

The EPA and the California Department of Environmental Protection have provided registration to Monterey Chemical Co. (18) for a product called Kaligreen®. A potassium bicarbonate fungicide for PM control, it is cleared for use on grapes, cucumbers, tobacco, roses, strawberries, and a wide range of other crops.(19, 20, 21) Directions for use include the addition of a sticker-spreader surfactant and a caution against use in acidic spray mixes. Since the product contains 30% potassium it is also touted for its fertilizer value.(22) One source of Kaligreen® is Peaceful Valley Farm Supply.(23)

Yet another potassium bicarbonate product, Remedy®, by Bonide™ (24), is now available from Gardener's Supply Co.(25) This formulation, which includes a surfactant oil, is labeled for use on ornamental, nut, and fruit trees, shrubs, and many vegetable plants. Said to control PM, black spot, leaf spot, anthracnose, phoma, phytophthora, scab, botrytis, and many other diseases, Remedy is particularly targeted toward rose growers.(26)

Various carbonates and bicarbonates have been proven effective against gray mold, the number one post-harvest disease of grapes. Researchers found that carbonates were more effective than bicarbonates at reducing gray mold (Botrytis cinerea) spore germination, and that sodium and ammonium bicarbonates were better than potassium bicarbonate.(27)

While industry was in the process of developing bicarbonate products for commercial and home horticulture, a number of recommendations for using kitchen-grade baking soda surfaced in print. These include:

  • J. Howard Garrett—a well-known horticultural columnist and radio personality in the Dallas, Texas, area—recommends baking soda sprays at a concentration of 4 teaspoons per gallon of water for control of PM, blackspot, brown patch, and other fungal diseases. He also suggests that a light soil spray of baking soda solution can suppress fungus gnat problems, while cautioning that overuse should be avoided because of possible negative effects (sodium accumulation and alkaline pH) on the soil.(28)
  • The authors of an organic pest control handbook suggest the same concentration mixture as Garrett, but advise the addition of an equal quantity of liquid dish soap or insecticidal soap as a surfactant.(29)
  • The P. Allen Smith Gardens website advises mixing 1 heaping tablespoon of baking soda, 1 tablespoon of dormant oil, and ½ teaspoon of insecticidal or dish soap in one gallon of water as a PM spray. Stating that plants should be well hydrated prior to spraying, this source recommends irrigating a couple days in advance.(30)


1. Williams, Greg and Pat Williams. 1993. Baking soda vs. powdery mildew: Not a new idea! HortIdeas. June. p. 62.

2. Williams, Greg and Pat Williams. 1985. Baking soda for powdery mildew control. HortIdeas. September. p. 101-102.

3. Anon. 1990. Baking soda can ward off fungus. Greenhouse Manager. June. p. 24.

4. Ziv, O. and T. A. Zitter. 1992. Effects of bicarbonates and film-forming polymers on cucurbit foliar diseases. Plant Disease. Vol. 26, No. 5. p. 513-517.

5. Williams, Greg and Pat Williams. 1992. More on baking soda/horticultural oil vs. fungal disease. HortIdeas. June. p. 69.

6. Hofstetter, Bob. 1993. Homemade pesticides. The New Farm. February. p. 14-16.

7. Moore, Sallyann Roberts. 1996. Bicarbonates offer effective disease control. Grower Talks. February. p. 72.

8. Ziv, O. and A. Hagiladi. 1993. Controlling powdery mildew in euonymus with polymer coatings and bicarbonate solutions. HortScience. Vol. 28, No. 2. p. 124-126.

9. Williams, Greg and Pat Williams. 1993. Baking soda and horticultural oil vs. powdery mildew. HortIdeas. May. p. 51.

10. Byczynski, Lynn. 1995. New ideas for a new year. Growing for Market. January. p. 1, 4-5.

11. Williams, Greg and Pat Williams. 1997. Sodium bicarbonate for control of mildew on grapes. HortIdeas. June. p. 70.

12. Otten, Paul. 1997. Can kitchen products control powdery mildew? Northland Berry News. Fall. p. 20.

13. Elmer, Wade H. and Frank J. Farandino. 1997. Managing powdery mildew of cucurbits. The Natural Farmer. Summer. p. 26-27.

14. Church & Dwight Co., Inc.
469 N. Harrison St.
Princeton, NJ 08543-5297


15. Anon. 1998. EPA approves reduced-risk fungicide. The Grower. December. p. 8.

16. Helena Chemical Co.
225 Schilling Blvd. Suite 110
Collierville, TN 38017
901 537-7280
Armicarb® is available in 5 and 25 lb. bags, for about $5/lb. Call the number above or visit the website to locate the Helena Chemical dealer nearest you.

17. W. A. Cleary Chemical Co.
1049 Corporate Rt. 27
Somerset, NJ 08875
FirstStep® is available in 5 lb. bags and 20 lb. cases. Call the number above for price information.

18. Monterey Chemical Co.
P. O. Box 35000
Fresno, CA 93745-5000

Kaligreen is available in 5lb. and 10lb. bags. Prices vary from dealer to dealer.

19. Anon. 1998. Powdery mildew fungicide. The Grower. March. p. 6.

20. Anon. 1999. EPA expands Kaligreen label. The Grower. August. p. 10.

21. Anon. 2000. Label Changes (Kaligreen) American Vegetable Grower. March. p. 14.

22. Anon. 1998. Peaceful Valley Farm Supply 1998-1999 Main Catalog. Peaceful Valley Farm Supply. Grass Valley, CA. p. 92.

23. Peaceful Valley Farm Supply
P. O. Box 2209
Grass Valley, CA 95945


24. Bonide Products, Inc.
Oriskany, NY 13424

25. Gardener's Supply Co.
128 Intervale Rd.
Burlington, VT 05401-2850

e-mail: info@gardeners.com

26. Anon. 1998. Fungus remedy. B.U.G.S. Flyer. Vol. 12, No. 1. p. 5.

27. Anon. 1999. Baking soda and gray mold. Conference notes: ESA and APS joint meeting. IPM Practitioner. April. p. 10-11.

28. Garrett, J. Howard. 1989. J. Howard Garrett's Organic Manual. Lantana Publishing Co. Dallas, TX. 104 p.

29. Ellis, Barbara W. and Fern Marshall Bradley. 1992. The Organic Gardener's Handbook of Natural Insect and Disease Control. Rodale Press. Emmaus, PA. 534 p.

30. Anon. 1997. Garden lore—Baking soda solution. P. Allen Smith Gardens. Hortus Ltd.


By George Kuepper, Raeven Thomas, and Richard Earles
NCAT Agriculture Specialists
Copyright © 2001 National Center for Appropriate Technology
Slot 102


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