The term additives is synonymous with the words boosters and supplements


Additives is a term used to describe the sugars, vitamins, hormones, fungi, bacteria, and any other substances used to improve plant growth.  Carefully following the additive instructions is important to determine the correct dosage and timetable for application.  Additives are available in many forms, such as liquids, crystals, granules, powders and others.  Most additives manufacturers have a website that provide additional information about their product.  It is up to the horticulturist to ensure using multiple additives do not carry any contraindications. 

Many additives that claim to boost plant growth and yields fall under the classification of hormones and therefore are considered plant growth regulators (PGR's). Please be very careful when selecting products to ensure that no dangerous PGR's end up in the cannabis you cultivate.



Mycorrhizal fungi

Mycorrhizal fungi refers to a class of fungi that forms a mutualistic relationship between mycelium of specific fungi and roots of plants.  Plants and mycorrhizal fungi operate as a single working unit in nature. The plant performs photosynthesis and other above-ground functions, and the fungi handle underground nutrition-gathering and protect the roots. This mutualistic association provides the fungus with relatively constant and direct access to carbohydrates, such as glucose and sucrose supplied by the plant. The carbohydrates are translocated from their source (usually leaves) to root tissue and on to fungal partners. In return, the plant gains the benefits of the mycelium’s higher absorbtive capacity for water and mineral nutrients (due to comparatively large surface area of mycelium:root ratio), thus improving the plant’s mineral absorption capabilities

Plant roots alone may be incapable of taking up phosphate ions that are demineralized, for example, in soils with a basic pH. The mycelium of the mycorrhizal fungus can, however, access these phosphorus sources, and make them available to the plants they colonize.

Generally speaking, mycorrhizal fungi are classified as two types, endomycorrhizal and ectomycorrhizal.  Endomycorrhizal fungi (more commonly referred to as endomycorrhizae) is one of the major types of known mycorrhizae.  Unlike ectomycorrhizae which form a system of hyphae that grow around the cells of the root, the hyphae of the endomycorrhizae not only grow inside the root of the plant but penetrate the root cell walls and become enclosed in the cell membrane as well. This makes for a more invasive symbiotic relationship between the fungi and the plant. The penetrating hyphae create a greater contact surface area between the hyphae of the fungi and the plant. This heightened contact facilitates a greater transfer of nutrients between the two.


Trichoderma are free-living fungi that are common in soil and root ecosystems. Recent discoveries show that they are opportunistic, avirulent plant symbionts, as well as being parasites of other fungi. At least some strains establish robust and long-lasting colonizations of root surfaces and penetrate into the epidermis and a few cells below this level. They produce or release a variety of compounds that induce localized or systemic resistance responses, and this explains their lack of pathogenicity to plants. These root–microorganism associations cause substantial changes to the plant proteome and metabolism. Plants are protected from numerous classes of plant pathogen by responses that are similar to systemic acquired resistance and rhizobacteria-induced systemic resistance. Root colonization by Trichoderma spp. also frequently enhances root growth and development, crop productivity, resistance to abiotic stresses and the uptake and use of nutrients. (G. E. Harman et al, 2004)



Bacteria are tiny, one-celled organisms – generally 4/100,000 of an inch wide (1 µm) and somewhat longer in length. What bacteria lack in size, they make up in numbers. A teaspoon of productive soil generally contains between 100 million and 1 billion bacteria. That is as much mass as two cows per acre.

Bacteria fall into four functional groups. Most are decomposers that consume simple carbon compounds, such as root exudates and fresh plant litter. By this process, bacteria convert energy in soil organic matter into forms useful to the rest of the organisms in the soil food web. A number of decomposers can break down pesticides and pollutants in soil. Decomposers are especially important in immobilizing, or retaining, nutrients in their cells, thus preventing the loss of nutrients, such as nitrogen, from the rooting zone.

A second group of bacteria are the mutualists that form partnerships with plants. The most well-known of these are the nitrogen-fixing bacteria. The third group of bacteria is the pathogens. Bacterial pathogens include Xymomonas and Erwinia species, and species of Agrobacterium that cause gall formation in plants. A fourth group, called lithotrophs or chemoautotrophs, obtains its energy from compounds of nitrogen, sulfur, iron or hydrogen instead of from carbon compounds. Some of these species are important to nitrogen cycling and degradation of pollutants.  

What Do Bacteria Do?

Bacteria from all four groups perform important services related to water dynamics, nutrient cycling, and disease suppression. Some bacteria affect water movement by producing substances that help bind soil particles into small aggregates (those with diameters of 1/10,000-1/100 of an inch or 2-200µm). Stable aggregates improve water infiltration and the soil’s water-holding ability. In a diverse bacterial community, many organisms will compete with disease-causing organisms in roots and on aboveground surfaces of plants.

A Few Important Bacteria

Nitrogen-fixing bacteria form symbiotic associations with the roots of legumes like clover and lupine, and trees such as alder and locust. Visible nodules are created where bacteria infect a growing root hair. The plant supplies simple carbon compounds to the bacteria, and the bacteria convert nitrogen (N2) from air into a form the plant host can use. When leaves or roots from the host plant decompose, soil nitrogen increases in the surrounding area.

Nitrifying bacteria change ammonium (NH4+) to nitrite (NO2-) then to nitrate (NO3-) – a preferred form of nitrogen for grasses and most row crops. Nitrate is leached more easily from the soil, so some farmers use nitrification inhibitors to reduce the activity of one type of nitrifying bacteria. Nitrifying bacteria are suppressed in forest soils, so that most of the nitrogen remains as ammonium.

Denitrifying bacteria convert nitrate to nitrogen (N2) or nitrous oxide (N2O) gas. Denitrifiers are anaerobic, meaning they are active where oxygen is absent, such as in saturated soils or inside soil aggregates.

Actinomycetes are a large group of bacteria that grow as hyphae like fungi. They are responsible for the characteristically “earthy” smell of freshly turned, healthy soil. Actinomycetes decompose a wide array of substrates, but are especially important in degrading recalcitrant (hard-to-decompose) compounds, such as chitin and cellulose, and are active at high pH levels. Fungi are more important in degrading these compounds at low pH. A number of antibiotics are produced by actinomycetes such as Streptomyces.    USDA NRCSS



Soil enzymes increase the reaction rate at which plant residues decompose and release plant available nutrients. The substance acted upon by a soil enzyme is called the substrate. For example, glucosidase (soil enzyme) cleaves glucose from glucoside (substrate), a compound common in plants. Enzymes are specific to a substrate and have active sites that bind with the substrate to form a temporary complex. The enzymatic reaction releases a product, which can be a nutrient contained in the substrate.

Sources of soil enzymes include living and dead microbes, plant roots and residues, and soil animals. Enzymes stabilized in the soil matrix accumulate or form complexes with organic matter (humus), clay, and humus-clay complexes, but are no longer associated with viable cells. It is thought that 40 to 60% of enzyme activity can come from stabilized enzymes, so activity does not necessarily correlate highly with microbial biomass or respiration. Therefore, enzyme activity is the cumulative effect of long term microbial activity and activity of the viable population at sampling. However, an example of an enzyme that only reflects activity of viable cells is dehydrogenase, which in theory can only occur in viable cells and not in stabilized soil complexes.

Why it is important: Enzymes respond to soil management changes long before other soil quality indicator changes are detectable. Soil enzymes play an important role in organic matter decomposition and nutrient cycling. Some enzymes only facilitate the breakdown of organic matter (e.g., hydrolase, glucosidase), while others are involved in nutrient mineralization (e.g., amidase, urease, phosphatase, sulfates). With the exception of phosphatase activity, there is no strong evidence that directly relates enzyme activity to nutrient availability or crop production. The relationship may be indirect considering nutrient mineralization to plant available forms is accomplished with the contribution of enzyme activity. Further research is needed to corroborate this information.

What you can do: Organic amendment applications, crop rotation, and cover crops have been shown to enhance enzyme activity.  Agricultural methods that modify soil pH (e.g., liming) can also change enzyme activity. Soil Quality for Environmental Health

For more information go to Soil Management Practices.



Plant hormones are chemical messengers that affect a plant's ability to respond to its environment. Hormones are organic compounds that are effective at very low concentration; they are usually synthesized in one part of the plant and are transported to another location.  They interact with specific target tissues to cause physiological responses, such as growth or fruit ripening. Each response is often the result of two or more hormones acting together.

Because hormones stimulate or inhibit plant growth, many botanists also refer to them as plant growth regulators. Many hormones can be synthesized in the laboratory, increasing the quantity of hormones available for commercial applications. Botanists recognize five major groups of hormones: auxins, gibberellins, ethylene, cytokinins, and abscisic acid.


Auxins are hormones involved in plant-cell elongation, apical dominance, and rooting.  They represent a group of plant hormones that regulate growth and phototropism.  A well known natural auxin is indoleacetic acid, or IAA which is produced in the apical meristem of the shoot. Developing seeds produce IAA, which stimulates the development of a fleshy fruit.  For example, the removal of seeds from a strawberry prevents the fruit from enlarging. The application of IAA after removing the seeds causes the fruit to enlarge normally.  IAA is produced in actively growing shoot tips and developing fruit, and it is involved in elongation. Before a cell can elongate, the cell wall must become less rigid so that it can expand. IAA triggers an increase in the plasticity, or stretchability, of cell walls, allowing elongation to occur.

1-naphthalene acetic acid (NAA)

Chemists have synthesized several inexpensive compounds similar in structure to IAA. Synthetic auxins, like NAA, are used extensively to promote root formation on stem and leaf cuttings. Gardeners often spray auxins on tomato plants to increase the number of fruits on each plant. When NAA is sprayed on young fruits of apple and olive trees, some of the fruits drop off so that the remaining fruits grow larger. When NAA is sprayed directly on maturing fruits, such as apples, pears and citrus fruits, several weeks before they are ready to be picked; NAA prevents the fruits from dropping off the trees before they are mature. The fact that auxins can have opposite effects, causing fruit to drop or preventing fruit from dropping, illustrates an important point. The effects of a hormone on a plant often depend on the stage of the plant's development.

NAA is used to prevent the undesirable sprouting of stems from the base of ornamental trees. As previously discussed, stems contain a lateral bud at the base of each leaf.  In many stems, these buds fail to sprout as long as the plant's shoot tip is still intact.  The inhibition of lateral buds by the presence of the shoot tip is called apical dominance. If the shoot tip of a plant is removed, the lateral buds begin to grow.  If IAA or NAA is applied to the cut tip of the stem, the lateral buds remain dormant.  This adaptation is manipulated to cultivate beautiful ornamental trees.

Indole-3-butyric acid (IBA)

IBA is a plant hormone in the “auxin”group.  It is applied exogenously and used as a plant growth regulator.  IBA exerts different effects on plant growth and development, e.g. regulating responses of plants against biotic and abiotic stresses, or increasing plant yield, but it is primarily implicated in adventitious root formation and widely used commercially for the induction of roots.


In the 1920's scientists in Japan discovered that a substance produced by the fungus Gibberella caused fungus-infected plants to grow abnormally tall. The substance, named gibberellin, was later found to be produced in small quantities by plants themselves. It has many effects on a plant, but primarily stimulates elongation growth. Spraying a plant with gibberellins will usually cause the plant to grow to a larger than expected height, i.e. greater than normal.

Like auxins, gibberellins are a class of hormones that have important commercial applications. Almost all seedless grapes are sprayed with gibberellins to increase the size of the fruit and the distance between fruits on the stems.  Beer makers use gibberellins to increase the alcohol content of beer by increasing the amount of sugar produced in the malting process. Gibberellins are also used to treat seeds of some food crops because they will break seed dormancy and promote uniform germination.


The hormone ethylene is responsible for the ripening of fruits. Unlike the other four classes of plant hormones, ethylene is a gas at room temperature. Ethylene gas diffuses easily through the air from one plant to another. The saying "One bad apple spoils the barrel" has its basis in the effects of ethylene gas.  One rotting apple will produce ethylene gas, which stimulates nearby apples to ripen and eventually spoil because of over ripening.

Ethylene is usually applied in a solution of ethephon, a synthetic chemical that breaks down and releases ethylene gas. It is used to ripen bananas, honeydew melons and tomatoes. Oranges, lemons, and grapefruits often remain green when they are ripe. Although the fruit tastes good, consumers often will not buy them, because oranges are supposed to be orange, right? The application of ethylene to green citrus fruit causes the development of desirable citrus colors, such as orange and yellow.  In some plant species, ethylene promotes abscission, which is the detachment of leaves, flowers, or fruits from a plant. Cherries and walnuts are harvested with mechanical tree shakers. Ethylenetreatment increases the number of fruits that fall to the ground when the trees are shaken. Leaf abscission is also an adaptive advantage for the plant. Dead, damaged or infected leaves drop to the ground rather than shading healthy leaves or spreading disease. The plant can minimize water loss in the winter, when the water in the plant is often frozen.


Cytokinins promote cell division in plants. Produced in the developing shoots, roots, fruits and seeds of a plant, cytokinins are very important in the culturing of plant tissues in the laboratory.  A high ratio of auxins to cytokinins in a tissue-culture medium stimulates root formation. A low ratio promotes shoot formation. Cytokinins are also used to promote lateral bud growth in flowering plants.

Abscisic Acid

Abscisic acid, or ABA, generally inhibits other hormones, such as the auxin IAA.  ABA helps to bring about dormancy in a plant's buds and maintains dormancy in its seeds. ABA causes the closure of a plant's stomata in response to drought. Water stressed leaves produce large amounts of ABA, which triggers potassium ions to be transported out of the guard cells. This causes stomata to close, and water is held in the leaf. It inhibits shoot growth and may stimulate root growth.  ABA is a gibberellin inhibitor.  When used in horticulture, ABA may help plants resist drought as well as improve performance, strength and productivity.



Amino acids are used by plants to make proteins.  These proteins are needed for enzymes, membranes and other cellular structures. Every plant like any organism needs certain components for growth over and above soil, sun, rain and air. The basic component of living cells is Proteins, with building block material, Amino Acids. Proteins are formed by sequence of Amino Acids.

Fig. 1. Schematic representation of amino acid transport between the sites of primary nitrogen assimilation and the import-dependent tissues. Amino acids synthesized in the root from inorganic forms of nitrogen or symbiotic relationships are transported to mature leaf tissue in the xylem. Amino acids synthesized in the leaf after primary assimilation, or arriving from the root in the xylem, are transported out of the leaf in the phloem to satisfy the needs of heterotrophic sinks. Import-dependent tissues include developing leaves, roots, cortical cells in the stem, seed and fruits, and apical meristems.  D.R. Bush, in: Singh, B.K. (Ed.), Plant Amino Acids: Biochemistry and Biotechnology, Marcel Dekker, New York, 1999, pp. 305–318

Fig. 1. Schematic representation of amino acid transport between the sites of primary nitrogen assimilation and the import-dependent tissues. Amino acids synthesized in the root from inorganic forms of nitrogen or symbiotic relationships are transported to mature leaf tissue in the xylem. Amino acids synthesized in the leaf after primary assimilation, or arriving from the root in the xylem, are transported out of the leaf in the phloem to satisfy the needs of heterotrophic sinks. Import-dependent tissues include developing leaves, roots, cortical cells in the stem, seed and fruits, and apical meristems.

D.R. Bush, in: Singh, B.K. (Ed.), Plant Amino Acids: Biochemistry and Biotechnology, Marcel Dekker, New York, 1999, pp. 305–318

Plants synthesize Amino Acids from the Primary elements, the Carbon and Oxygen obtained from air, Hydrogen from water in the soil, forming Carbon Hydrate by means of photosynthesis and combining it with the Nitrogen which the plants obtain from the soil, leading to synthesis of amino acids, by collateral metabolic pathways. Only L-Amino Acids are part of these Proteins and have metabolic activity. The requirement of amino acids in essential quantities is well known as a means to increase yield and overall quality of crops.

The application of amino acids for foliar use is based on its requirement by plants in general and at critical stages of growth in particular. Plants absorb Amino Acids through Stomas and is proportionate to environment temperature. Amino Acids are fundamental ingredients in the process of Protein Synthesis. About 20 important Amino Acids are involved in the process of each function. Studies have proved that Amino Acids can directly or indirectly influence the physiological activities of the plant.

Amino Acids are also supplied to plant by incorporating them into the soil. It helps in improving the microflora of the soil thereby facilitating the assimilation of nutrients. Foliar Nutrition in the form of Protein Hydrolysate (Known as Amino Acids Liquid) and foliar spray provide readymade building blocks for Protein synthesis.

Figure 1. and the below excerpt are from a review on amino acid transporters in plants. These insights further support the important role amino acids play in plant growth. "Amino acids are the currency of nitrogen exchange in plants. Although inorganic salts of nitrogen are initially acquired from the soil solution, these compounds are rapidly incorporated into amino acids in root or mature leaf tissue. While some of the newly synthesized amino nitrogen is used in protein biosynthesis or as the precursor of other essential nitrogen containing molecules in these tissues, most is transported in the plants vascular system from the sites of primary assimilation to satisfy the nutritional needs of other organs that do not play a major role in nitrogen assimilation. Those tissues, which include developing leaves, meristems and reproductive organs, must import amino acids to support growth and development. Amino acid transport also plays a key role in leaf senescence and seed germination. In rice, for example, as much as 60% of the amino acids delivered to the developing seeds are derived from amino acids recovered from senescing leaves. Clearly, amino acid transport is a fundamental activity in plant growth."

Biochimica et Biophysica Acta (BBA) - Biomembranes Volume 1465, Issues 1–2, 1 May 2000, Pages 275–280



Humic substances are a group of complex organic compounds consisting of humic acids, fulvic acids, natural salts of these acids (e.g., calcium humates), and sponge-like substances called humin.  Humic substances (which includes humic acids) naturally constitutes a large fraction of the organic matter in soil, and is formed through the process known as “humification.” Humification is the natural conversion of organic matter into humic substances by microorganisms in the soil.

This process begins with microorganisms separating out sugars, starches, proteins, cellulose, and other carbon compounds from the organic matter. The microorganisms use these components in their own metabolic processes. Subsequently, the microorganisms transform the majority of the organically bound nutrients into a mineral form that areused by plants and other organisms. The portions of the organic matter that are not digested by the microorganisms accumulate as humic substances.

Humification does not occur in one step, but involves an intermediate substance called compost, which consists of a mixture of humic substances and partially decomposed organic matter. As the humification process proceeds, various chemicals dominate at different times until conversion to humic substances is complete

Humic and fulvic acids have been shown to perform 4 plant functions:

  1. Increase cell permeability, which allows for more optimal nutrient uptake
  2. Act as chelating agents to facilitate nutrient availability within the plant.
  3. Providing structure for the soil by acting as a colloid.
  4. Providing a cation-exchange site for elements to bind with the plants roots.



A carbohydrate is a biological molecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1. Carbohydrates are known as sugars, starches, saccharides and polysaccharides. 

The following chemical equation demonstrates that when carbon dioxide and water combine in the presence of light, the leaves produce oxygen and carbohydrates in a process known as photosynthesis:

6CO2 + 6H2O → C6H12O6 + 6O2

To put it simply, carbohydrates are the primary and most abundant products of light-energy transformation by plants. Leaves take the solar energy from your lamps or the sun, the CO2 from the air, and the water from the growing medium to produce the energy your plants need to grow and thrive. 

Carbohydrates represent roughly a quarter of all organic soil matter, a substantial amount of which is derived from polysaccharides in roots and plant debris. Carbohydrates can be as simple as sucrose, which is table sugar, or as complex as cellulose, which is the tough, fibrous polymer that plants are made of. All carbohydrates end in –ose. All contain energy. Furthermore, plants utilize this versatile source of energy in a variety of ways. They use carbs to grow tissues and build construction materials of all kinds: roots, stems, leaves, blossoms. In fact, they metabolize carbohydrates into almost everything imaginable, from starch, an energy accumulator, to THC. Carbs are even involved in the synthesis of DNA—deoxyribonucleic acid, whose name is derived from deoxyribose, a carbohydrate.

Any excess carbohydrates your plants do not burn off, they store up in specialized bodies called vacuoles. These reserves are made readily available later on when your plants channel all that energy into producing denser flowers and fruits. Indeed, carbohydrates play their most critical role in the weeks just before harvest. It is during ripening that buds make their biggest weight gains while burning through those precious energy reserves.  Because of this, an enormous amount of metabolic energy is expended on manufacturing carbs throughout the late vegetative and early flowering stages. Once ripening sets in, carbohydrate production all but stops, and plants must rely almost solely on their carbohydrate reserves. 

An important point to note is that plants roots do not uptake carbohydrates.  Instead, the plant uses photosynthesis to manufacture carbohydrates and then sends these sugars into it's root system to perform an energy exchange with the soil bacteria and fungi.  When you add carbohydrates to the soil, you are in essence feeding the soil microbiology that helps promote nutrient uptake. 



Vitamin B

The University of California, Davis reports that there is no basis to the claim that vitamin B-1 benefits plants by stimulating root growth or reducing transplant shock as many advertisements claim. By contrast, Advanced Nutrients' researchers assert that application of B vitamin supplements produces stronger plants with a higher yield than those without the treatment. More research is needed to establish the connection, if any, between plant growth and vitamin B.

Vitamin C

University of California, Riverside biochemistry professor, Daniel Gallie indicates that vitamin C appears to increase a plant's smog tolerance, improve the process of photosynthesis and make the fruit more nutritious. His findings report that vitamin C supplementation acts as a protection against the ozone, the most damaging part of smog, decreasing brown spots, avoiding stunted growth and raising crop yields. He cautions that more research is needed in this area, however.

Vitamin E reports a study from the University of Toronto and Michigan State University that indicates vitamin E supplements decrease a plant's susceptibility to cold temperatures. The result could be the development of cold-resistant plant species, which would benefit gardeners in cooler climates by producing better crops and yield. Cool-weather gardeners can experiment with how applying vitamin E to developing plants affects the longevity or growth of their crops.

Selected References

Nature Reviews Microbiology 2, 43-56 (January 2004). Authors: Gary E. Harman, Charles R. Howell, Ada Viterbo, Ilan Chet & Matteo Lorito