Reeferman Genetics – Chapter 6 – Grow Top Shelf Buds

Chapter 6 of a 14 part weekly series discussing crop nutrients and fertilizers. Follow step by step to grow top shelf harvests like a pro. The information and instructions are highly scalable. These proven and well developed methods and technologies will work for anyone. Whether you want to grow some personal crops of buds at home or if you intend to fill a warehouse.

Fertilizers are fuel for the fire in your cannabis genetics.

Your choice in crop nutrients and fertilizers as well as how you apply them can have a strong influence on growth rates, yields and crop quality in a hydroponics system. However, good nutrient programs and quality fertilizers do not guarantee you great harvests, your crop genetics are where great results begin.

Hydroponic Fertilizer Basics

In our growing model, whether you choose coco or stick with rockwool as the growing medium, you will want to source fertilizers that are intended for hydroponics. We do not recommend using organic fertilizers, additives, or crop inoculants (like beneficial bacteria, enzymes, fungi, etc0 in hydroponics.

Why not organics?

We like organic grown crops, please do not get us wrong. However, organic soils, nutrients and additives are not clean, sterile, or hygienic and belong outdoors or in a greenhouse. They absolutely do not belong in recirculating hydroponic reservoirs indoors. That is because organic gardening only works when microbial life is healthy and in the right balance.

Most organic nutrient sources do not typically have nutrients that are readily available to plants. The nutrient building blocks need to be broken down and converted by biological life. This is what happens naturally in healthy soils or compost, NOT IN YOUR HYDROPONIC RESERVOIR OR HYDROPONIC GROWING MEDIUM. The natural life you are counting on will not thrive or live in the right balances in a water tank. To keep this short, if anybody tells you to add organic products to a recirculating hydroponic reservoir or to a growing medium like rockwool, DON’T LISTEN.

Organics might work for a few days, or maybe even a week or two, after that your plants will begin to suffer, develop root rot and your reservoir will fill with smelly sludge and strange new life forms that cause nothing but trouble for you and your crop. Fouled up growing media, irrigation lines, tray surfaces, pumps, etc. will need a lot of cleaning or potentially replacement. Do not say we did not warn you. So, let us leave it at that, OK.

What’s Good About Hydroponic Nutrients?

Cannabis Hydroponic healthy rootsThe following benefits from High quality fertilizers that are made for use in hydroponics offer:

Macro and Micronutrients can be readily taken up by plants. There is not a dependency on biological life as the sources of nutrients are supplied in their plant available forms and in the right balances.

Hydroponic nutrient sources, whether purchased as a liquid formulation or in dry soluble powder forms are 100% clean and sterile; there is little to no risk of contamination of your system or plants.

Fertilizer sources intended for hydroponics are typically of a higher grade versus field agriculture fertilizers. They are less likely to burn or toxify your plants when used as directed. In fact, many of the individual nutrient sources used in good quality hydroponic nutrient formulations are Food Grade. You may be eating them already in places as food additives.

Hydroponic Nutrient Formulas

Hydroponic nutrient formulas help provide a stable pH and level of dissolved solids for plants. These are important factors in determining how well a hungry and fast growing crop can take up essential plant nutrients to fuel fast growth and heavy buds.

No bad aromas or foul odors are created in the growing area with soluble high quality hydroponic fertilizers; they will not bung up your irrigation lines or growing equipment easily too.

Harvests taste and smoke super clean. With high quality hydroponic crops you are tasting and smelling the plant’s essential oils (terpenes or “terps”) from the genetics of the plant. This is much better than harsh tasting and burning cannabis grown with lower quality fertilizers and funky organic additives. Who knows what it is you might be tasting and smoking there.

When sourced from a reputable manufacturer, your hydroponic nutrients and additives will be consistent from batch to batch. Once you find or dial in a feed program you like for your cannabis plant genetics, crops can be grown to consistent AAAA+ quality each time you grow.

Crop Feeding Programs

Cannabis Hydroponic Healthy rootsThere are a lot of choices if you want to buy hydroponic fertilizers and use them as directed in a crop feeding program or “nutrient recipe”, etc. Buyer beware, companies ARE in the business of selling you as much as your plants can possibly use, and sometimes beyond. Avoid programs that call for lots of different additives, especially if you are just starting out.

Remember, one of the big advantages of choosing recirculating hydroponics is that plant roots will be getting lots of oxygen, clean water and have essential elements supplied in forms favored by plants for fast uptake. There is not much to improve on in this equation.

Our Fertilizer and Nutrient Recommendation

We recommended you stick with complete base nutrients stated for use in hydroponics (like Veg A&B, Bloom A&B or three parts like Grow, Bloom and Micro).

For additives, you might add a Calcium-Magnesium (Cal-Mag) supplement if you use reverse osmosis filtered water (recommended, and we will talk about that some more), and a Bloom Booster (something that adds extra Phosphorous, Potassium and

Magnesium without adding much extra Nitrogen). Vitamins like B-1 supplements can have some benefits too, however, usually more so in early plant development.

Some additives intended for hydroponics may add hormones or growth regulators for plants. We do not recommend these. Kelp extracts can be effective as foliar sprays, although are not necessary when healthy growing strong cannabis genetics are receiving all the vital elements they require from fertilizers.

NPK Basics

Here is a quick lesson in fertilizer basics. Plants need the following elements from complete fertilizer sources. Loosely ranked in order of amounts usually needed for healthy plant development: Nitrogen (N), Phosphorous (P), Potassium (K), Sulfur (S), Calcium (Ca), Magnesium (Mg), Iron (Fe), Boron (Bo), Copper (Cu), Manganese (Mn), Zinc (Zn) and Molybdenum (Mo).

This is not to say there are not any other elements needed. These other elements are required in small amounts and are usually found as impurities in the water or other fertilizer components, for example Chloride (Cl). Other elements may come from the air around the roots (oxygen, hydrogen) or from the air around the leaves (Carbon Dioxide i.e., Carbon).

Do not worry too much about understanding chemistry, just make sure that you are applying a fertilizer that is complete and intended for hydroponic use; it will have everything your plants need and supplied in the right ratios and forms.

A Note on Chelates

Chelates (pronounced “Key-Lates”) are elemental chains found in higher quality fertilizer formulations. All or most of the micro elements (iron, boron, copper, manganese, zinc, and molybdenum) should be supplied in “Chelated Forms”. Ask your supplier or check the fertilizer label. The most common chelate compound used is “EDTA”, however “DTPA” and “EDDHA” are also used in hydroponic nutrient formulations.

What Do Chelates Do?

Notice that micro elements we listed are “metals”. Plants need these elements just as much as they do others, just in small amounts (that is why they are referred to as “micro” nutrients).

However, when supplied as simple elements, micronutrients are hard for plants to take up because they have an electrical charge to them, typically a “+” positive charge. To neutralize this charge, a chelate is combined with the element (they bond together). When the plant takes up the neutralized element like iron (that would normally have a triple + electrical charge), it strips away the chelate chain and drops the chelate chain back into the solution. In simple terms, chelated trace elements help make sure your plants have easy access to all the vital elements they need, with no interruption for fast and healthy growth, root development and blooms.

Fulvic Acid is an example of a natural chelator. Note that sometimes chelated nutrients are referred to as “complexed” nutrients. Just like iron supplements intended for human or animal diets.

How to Use Hydroponic Nutrients & Crop Feeding Programs?

Cannabis plant hydroponic feedingFollow the label or feed chart, remember that it is usually better to start about 50% weaker than recommended. It is quite easy to correct underfeeding in hydroponics. Simply add a little more and you will see your plants green right up within hours or a day. Overfeeding can damage plants, stunt growth, or create nutrient imbalances that might be difficult to diagnose (to a newbie it could look like a deficiency).

The complete hydroponic fertilizer you choose will supply everything in the right ratios. Follow the weekly recommendations designated into several or all the following growth phases:


Early Vegetative Growth (AKA Pre-Veg)

Vegetative Growth

Transitional/Early Bloom




Do not be intimidated by all this discussion of elements, chemistry, different phases, etc. Follow the label or chart sparingly and compare what the dilution ratio yields in terms of TDS/PPM or EC in the guidelines we provide below, and you will do fine.


These are different terms or measures used to designate, quite specifically, how strong a fertilizer solution is. You will want to buy an electronic device to make this measurement, there are lots to choose from. It is important to note that EC (Electrical Conductivity) is the best one to use or get acquainted with. It is the base measurement that others like PPM (parts per million) or TDS (total dissolved solids) are converted from. Most of the time when fertilizer manufacturers talk about PPMs it is on the “700 Scale” where 1.0 EC is equal to 700 parts per million.


Cannabis Hydroponic monitoring phThis is an important factor. In most basic terms it is the measurement of acidity to alkalinity of your crop nutrient solution and growing medium, measured from 0 to 14 with 7.0 being neutral (distilled water). The nutrient solution should be maintained between a 5.5 to 5.8 pH range for optimal nutrient uptake in rockwool or coco coir. Out of this range, some nutrients become unavailable while others more available. Keeping the right pH range keeps nutrient uptake balanced, avoiding crop nutrient deficiencies or imbalances. Do not sweat this too much. Measuring and adjusting the pH is simple and inexpensive using “pH Up” (alkaline, potassium hydroxide) and “pH Down” (acidic, phosphoric acid).

Monitoring & Measuring EC & pH

You can spend a LOT on expensive monitors, automatic dosers, etc. for hydroponics. If you are just getting started and want great results and reliable readings without calibrating your monitoring equipment constantly you cannot go wrong with using a Bluelabs “Truncheon”. A little more than a hundred dollars to measure your EC/PPMs and a simple liquid test kit for pH. The General Hydroponics test kis is just a few dollars and is accurate enough.

Crop Feeding Recommendations for Hydroponic Cannabis in Rockwool

The following will give you a good baseline to work with for the different cannabis crop phases we touched on earlier in this section.


Seeds do not need any fertilizer at all. After germination, once the first set of true leaves emerges, 0.3 to 0.5 EC vegetative growth fertilizer is plenty.

It is advised to presoak the rooting medium in a mild nutrient solution when root clones. A solution from 0.5 to 0.7 EC of a complete hydroponic vegetative formula.

Early Vegetative Growth (AKA Pre-Veg)

This is an important phase, usually lasting only a week or so. Here plants are transitioning from life in propagation conditions (little air movement, high humidity) to drier conditions with more air flow. This is a critical time to develop a sturdy root system that will support small plants as conditions become more intense later. 0.5 to 0.7 EC using a complete vegetative formula for hydroponics is recommended.

Vegetative Growth

Plants are established with good root systems and are ready to increase in size, number of shoots. They will fill the final container size or grow cube with roots before flowering is initiated. Vegetative hydroponic formulas can be supplied from 1.0 EC gradually increasing up to 1.4 to 1.8 EC. This will depend on how hungry the genetics are in your growing environment and how big the plants are. Bigger plants need more fertilizer.

Transitional/Early Bloom

This is the crop development that immediately follows shortening day length and increasing dark hours to initiate budding in regular cannabis genetics. Auto flower strains will initiate budding all on their own, regardless of photoperiod. Your crop is going through profound physiological changes at this time. 1.4 to 2.0 EC is recommended using a half and half combination of Veg and Flower A&B formulations or using equal parts of each Grow, Bloom and Micro in three part fertilizers.


Cannabis hydroponic bloom boostUsually a week or two after initiating the budding cycle flowers begin to form. At this time plants can be fed with complete hydroponic bloom fertilizer formulations. Adding a bloom booster can further help to enhance results. Bloom boosters should be used sparingly and are available for early, peak, and ripening stages. Gradually increase fertilizer concentrations through the early to late bloom stages. Typically, from 1.8 all the way as high as 2.6 EC. If you are unsure where the feeding threshold is for your strain, it is best to stay below 2.2 EC (including any additives).


Ripening period when flowers are fully formed and swell as they begin to reach maturity usually last the final two weeks. At this point, it may not look like plants are growing much. However, during this period the mass of the flowers is on the increase. Your patience will be reflected in the final dry weight of the harvest of buds as well as qualities like potency, flavor, and aroma. Plants are transferring stored nutrients into the buds during ripening, and do not need feeding strengths to be as strong. Too much fertilizer at this stage can hinder aroma and flavor although it may add density to cannabis flowers. An EC of 1.4 to 1.8 EC is typically a good level for most strains at ripening.


Traditionally, cannabis growers do not feed their crop any fertilizer the final week or two before harvest. This is said to help improve tastes and aromas in the dried buds. While it is often the case in traditional soil gardens or where organic fertilizers are used, it is not necessary following our model using hydroponic nutrients in rockwool. At most running pure pH adjusted water (5.5 to 5.8 for rockwool or coco) for a few days before harvest is recommended. Keeping plants lightly feeding during ripening will improve the density and harvest weight of your buds. Still delivering clean burning and tasting flowers that did not have any funky stuff added to them to begin with.

Continue reading “Reeferman Genetics – Grow Top Shelf Buds” by clicking on a chapter below.