Cannabis & Hemp

Using Cannabis Specific Bloom and Flower Enhancers

Throughout the growing process, cannabis cultivators make various changes to their garden’s environmental conditions, such as lighting and nutrition, to best suit the need of their plants. One of the first things a new grower learns is the different light cycles required by the vegetative and flowering stages of growth. In addition to the differing light cycle requirements, cannabis plants have different nutritional needs, depending on which stage of growth they are in. Once the flowering stage has been initiated, a cannabis grower should change their feeding regimen to fit the particular micro-stage of flowering the plants are in. The flowering or blooming stage of growth for cannabis plants can be broken down into three micro-stages: early flowering, mid-flowering, and ripening or late flowering. In order to boost yield and quality, many cannabis growers use different fertilizer additives for each of the three micro-stages within the flowering stage.

The Foundation: A Good Base Fertilizer Regimen

Before experimenting with various blooming additives, a cannabis grower needs to provide his or her plants with a good base fertilizer regimen. A solid base fertilizer will contain all of the essential elements needed for healthy plant development. Most base fertilizers are sold as either a “grow” or “bloom” formula. Although these base fertilizers are designed for different stages of growth, they both should contain all of the essential elements plants need. Cannabis plants need a higher percentage of nitrogen during the vegetative stage to grow fast and healthy. During the flowering stage, more emphasis is put on flower development than fast, green growth which is why blooming fertilizers contain a ratio of N-P-K more suitable for flower production. Generally speaking, a “bloom” base fertilizer will have less nitrogen and more phosphorus and potassium than a “grow” fertilizer. A quality “bloom” base fertilizer helps build the foundation that will maximize flower size and density. After a quality “bloom” base fertilizer is selected, a grower can focus on fine-tuning his or her feeding regimen with flowering additives.

Flowering Additives

As previously mentioned, the flowering stage for cannabis plants can be broken down into three parts. It makes sense then that there are three types of flowering additives that a grower can employ during his or her crop’s flowering stage. The three categories of flowering additives are: initiators, mid-blooming additives, and ripening additives.


Blooming initiators are products specifically designed to assist with the formation of flower sets during the early flowering stage. As a cannabis plant transitions into the blooming stage, it produces specific hormones for flower production. Most blooming initiators target these particular hormones. Normally, a blooming initiator contains a high percentage of phosphorus and potassium, usually derived from a chemical compound such as monopotassium phosphate. Blooming initiators rarely, if ever, contain nitrogen and should be carefully used as directed as they can cause nutrient lockout and toxicity if used incorrectly. By speeding up the onset of flowers, many blooming initiators can actually reduce the amount of time it takes for the plants to reach maturity. In other words, using a blooming initiator may lead to harvesting a crop earlier.

Mid-Flowering Additives

Mid-flowering additives are products designed to be used during the time of actual fruit and flower production or the mid-flowering stage. These products are meant to either boost or enhance hormonal production and/or supply a higher amount of nutrients commonly used during that particular stage. For most flowering plants, an increase of phosphorus and potassium will heighten hormonal responses, creating larger yields. The most beneficial mid-flowering enhancers contain slightly more potassium than phosphorus and are most effective when used from the time fruit or flowers first appear until two or three weeks before harvest. Like flower initiators, mid-flowering enhancers do not contain nitrogen. Most mid-blooming additives are derived from chemical compounds, such as monopotassium phosphate, potassium sulfate, potassium hydroxide, and magnesium phosphate.

Ripening Additives

Ripening additives are specific to the last two or three weeks before harvest. Like the mid-flower enhancers, many of these products contain a significant amount of phosphorus and potassium. These products are also commonly derived from the same chemical compounds as the mid-flowering additives. Some ripening additives target specific hormones created during the plant’s final weeks of life. Carbohydrate formulas, or flower “sweeteners”, are usually used as ripening additives and target flavor and potency enhancement. Carbohydrate formulas can be derived from a wide variety of sugars, including deoxyribose, xylose, xylulose, ribose, lyxose, maltose, galactose, and glucose.

Specialty Additives

In addition to base fertilizers, initiators, mid-flowering additives, and ripening additives there are specialty additives that can help boost cannabis plant’s flower size and density. Enzyme formulas, amino acids, humic/fulvic acids, microbes, and vitamins are sometimes found in base formulas, but can also be added individually to maximize performance. Most specialty additives can be used throughout the entire flowering stage, with the exception of flower hardeners. These specialty additives must be used as directed toward the end of the flowering cycle and are designed to do one thing: increase flower density.

Blooming Additives for Organic Growers

The vast majority of blooming additives are derived from chemical compounds and do not meet the standards for organic crop production. Cannabis growers who wish to grow organically can still “boost” their bloom by using organic ingredients throughout the flowering stage. Some of the most prevalent organic bloom boosters are formulas derived from guano, alfalfa, protein hydrolysate, and kelp.


Bat and seabird guano have been used to boost fruiting/flowering since the beginning of indoor horticulture. Guano with a high percentage of available phosphorus helps trigger flowering hormones within cannabis plants and contributes to an increase in flower sets. There have been many great advancements in the harvesting and extraction methods used by guano suppliers, many of which help preserve the powerful elements once lost due to outdated methods. One extraction method is “guano tea”; a liquid guano formula that contains many of the beneficial nutrients and microorganisms found in the guano. Liquid guano extracts are more easily absorbed by a plant and give a grower the option of foliar or root feeding. Liquid guano also gives a gardener more control over dosage; unlike guano that is directly amended into the soil or medium. Using a tea also enables the horticulturist to select which micro-stage(s) within the flowering stage he or she wishes to administer the guano. Typically, guano with a high percentage of available phosphorus would be used during the early flowering and mid-flowering stages.

Alfalfa Extracts

Another organic extract used by organic purists to boost flower production is alfalfa. Alfalfa has great nitrogen to carbon ratio, contains a variety of trace elements, and has been shown to promote large flowers. Alfalfa contains triacontanol, a growth hormone that is thought to speed up the rate of photosynthesis by increasing the amount of CO2 a plant can process. Many studies have shown an increase in flower site production and overall yield when using an alfalfa extract. Most alfalfa products contain nitrogen so their use should be discontinued about halfway through the mid-flowering stage.

Protein Hydrolysate

Protein hydrolysate is organic matter (usually soy protein) broken down into the essential L-amino acids. Amino acids are the building blocks for the proteins and enzymes that directly influence the structure and metabolism of plants. Supplementing a protein hydrolysate during the blooming period will enhance the utilization of other nutrients, boost the plant’s immune system, increase plant respiration, and reduce stress. Protein hydrolysate is a multifaceted additive that increases fruit/flower production in many different ways. Most protein hydrolysate formulas can be used throughout the entire flowering stage.

Kelp Extracts

Due to its high hormone content, kelp has been used for many years by indoor horticulturists. Although kelp was once rarely used as a bloom booster, some of the kelp formulations available today are specifically designed to do just that. When harvested at the correct time or in a particular manner, kelp extracts will contain a variety of hormones that help trigger flowering and ripening. Kelp also contains a high amount of trace elements which are beneficial in the fruiting/flowering stage. Kelp extracts that are specific to bloom stimulation will encourage rapid cell division during flowering and increase the production of specialized sugars found in fruit or flowers. It is important to select a kelp formula that is designed specifically for blooming or you could end up promoting vigorous growth during a cannabis plant’s ripening stage. Instead of dense, tight flower development, the result would be separated, wispy cannabis flowers.

Using blooming additives in addition to a solid base fertilizer is a great way for cannabis growers to fine-tune their feeding regimens. If all else is equal, plants given the proper blooming boosters at the appropriate time will produce more flower sets along with larger, denser flowers. Blooming additives are popular among cannabis cultivators and there is no shortage of product choices. In other words, there is a plethora of both conventional and organic blooming additives from which to choose. Most blooming additives are compatible with any base fertilizer so growers can get creative. Experimenting with products from various manufacturers is the best way for a cannabis grower to find out what works best for his or her particular crop.

Eric Hopper resides in Michigan’s beautiful Upper Peninsula where he enjoys gardening and pursuing sustainability.

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