Maximize Cannabis Yield: The Flowering Phase

The end is almost in sight, and in just another couple of months of blossoming we will be ready to get our sheers out of the cupboard. In order to get the very best out of each plant we need to tune all the possible factors and harmonise them with each other.

Budding stage cannabis plants require large amounts of nutrients. Using an enriched soil or nutrient solution dissolved in water ensures that the plant is getting enough nutrients. In order to understand the finishing process, it helps to know how the plant absorbs nutrients.

The roots of the cannabis plant are connected to the two vascular (think circulatory) systems: the xylem and the phloem.

The xylem carries water from the roots to the branches and leaves. A combination of surface tension and adhesive forces, formally known as capillary action, allows the plant to pull the water up the stem against gravity.

The phloem is the part of the system that carries sugars, hormones, enzymes and wastes from the upper canopy down to the lower portions of the canopy, the stem and ultimately the roots. The roots flush and exude sugars, enzymes and wastes that are digested by micro-organisms in the rhizosphere, the area surrounding the roots that supports micro-organisms including mycorrhizae. There is no indication that the phloem carries raw nutrients, the dissolved solids that make up fertilizers, out of plants.

Since cannabis is such a valuable crop it is sensible that farmers try many methods and techniques for enhancing crop quality and yield. Fertilizer companies have introduced dozens of products for bud enhancement, many of which are described below. The companies have followed two paths, nature and science.

Well-known growth and flower enhancers such as humic acid, kelp, molasses and sugars, guano, and mycorrhizae increase crop performance by enhancing the root environment, which increases ability to absorb water and nutrients that stimulate the plant’s growth.

Formulas dependent on the new botanical sciences include: amino acids, vitamins SAR stimulators, as well as plant hormones to increase quality and yield while shortening ripening time.

In the very first weeks of flowering, your cannabis plants will be in the transition stage. Thinking that winter is not far away and that she will soon have to carry a big load of bud, your plant will likely grow rapidly. Some strains can almost double in height during this time. Because of the fast growth that your plant is undergoing now, this early flowering phase is also known as the stretch phase.

While your plant is putting in quite some overtime to gain size and height, she will grow a number of new leaves mostly at the top of the main colas. Your cannabis plant is busy growing “green stuff,” like leaves and stems so she can become stronger and sturdier.

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Although your plant has officially entered the flowering phase, she will now have an increased need for growing nutrients. You should not abruptly change your nutrient schedule and use flowering nutrients from one day to the next. It is usually recommended that you continue to give growing nutrients for at least one more week once flowering starts.

You shouldn’t introduce blooming nutrients until your plants actually start to flower.

This means that usually, the first week after you’ve switched to a 12/12 cycle, you keep feeding vegetative nutrients…

And once you start seeing the first real flowers…NOW is the time to start feeding your plants with blooming / flowering nutrients.

During the flowering phase, you have to switch to bloom fertilizer. Some growers keep giving their plants grow fertilizer in the first and sometimes in the second week of the flowering phase because it is a kind of transition period and the plants still need building blocks to grow quickly. This will make the plants grow a bit taller. It all depends on what you want. By managing your use of fertilizer, you can control the size of your plant. If your plants already have the right size and you want to keep them smaller (because for instance space is limited), immediately start giving them bloom fertilizer. If your plants are still a bit small and space is not used optimally, you can continue administering grow fertilizer. They will grow a bit taller. The differences are not extreme, but a couple of centimeters can make quite a difference.

After a blooming period of three weeks, the plants have achieved their maximum size. They will no longer grow in height and width but will start forming buds. It is really important to administer blooming fertilizer then because the plants need more phosphorus and potassium. These are important building blocks for a good bud formation. PK 13/14 is a mixture high in phosphorus/potassium that stimulates flowering and fruiting. It is usually indicated on the bottle how much you have to administer. Make sure you do not give the plants too much, otherwise you risk overfertilizing them.

Even if you think that you are giving the right nutrients, the plants may lack something. If so, you can administer foliar feeding to your plant. The nutrients are rapidly absorbed in this way and any nutritional deficiencies are corrected quickly. The chance of overfertilizing is minimal when administering foliar feeding. When growing inside, the best moment to administer foliar feeding to your plants is half an hour before the lamps go on. The light of the lamps is very powerful from the beginning, so you run the risk of burning the leaves if they are still too wet. Outdoor plants are best being administered foliar feeding early in the day, before the sun is too strong. It’s no use giving them feeding when there is no light because then the plants don’t grow and they don’t need extra feeding. Besides that, you increase the risk of mold if they are too wet. Foliar feeding has to be sprayed on top of the leaves, once or twice per week. When giving foliar feeding, you also have to watch your plant closely to discover which nutrients it needs.

Finishing Products For Your Cannabis Plants

All finishing companies keep their formulas proprietary. However, they all work based on one of two theories:

They either bind the nutrients so they are no longer available to the roots (whether they remain or are washed away).

They make the salts more soluble so they flush out of the soil easily.

The following chart lists a range of finishing products readily available in stores and online. This chart and the appendix that follows list the specific ingredients comprising various finishing formulas.

ALGAE EXTRACT: Kelp extract

AMINO ACIDS: Primarily glutamine and cysteine, but includes others. May be absorbed through the root system, increasing stress tolerance, growth, yield and vitality.

AMMONIUM MOLYBDATE: Molybdinum (Mb) micro-nutrient

AMYLASE: An enzyme that acts as a catalyst for breaking down starches, turning them into sugars. These sugars provide a source of energy for the plant


AZOMITE: A natural mineral complex that stimulates growth.

B VITAMINS: Use of B Vitamins noted in literature or practice.

B1 VITAMIN: Touted as a stress relief for plants. Proven to have no value.

B2 VITAMIN: Also known as Riboflavin. There is no direct literature or note of its use in plants, which produce it in abundant quantities. However, it is known to protect some organisms from UV light

BAT GUANO: Source of organic N or P

BONE MEAL (STEAMED): Moderate release source of P (N:1.6-2.5, P:21, K:0.2)

CACO3: Calcium carbonate, source of Ca

CARBOHYDRATES: Simple sugars such as glucose or dextrose that plants can uptake

CARROT (WILD, AKA QUEEN ANNE’S LACE): Ferments into amino acids that stimulate flower growth

CHARCOAL: Soil conditioner that stimulates plant growth.

CHELATED: Many micro-nutrients are metals that have little availability. When bonded with other elements (chelation) they become much more available.

CHITOSAN: Found in crustacean shells, insect exoskeletons and fungus cell walls. Plant growth enhancer, and bio-pesticide substance that boosts the innate ability of plants to defend themselves against infections .

CITRIC ACID: Vitamin C. When sprayed under stress conditions, improves growth and internal citric acid concentration, and also induces defense mechanisms by increasing the activities of antioxidant enzymes. May play a positive role in stress tolerance.

CYSTEINE (L): An amino acid high in sulfur. Effective against bacterial infections in plants and may stimulate terpene production.

DOLOMITE: Mined combination of Ca (lime) and Mg

EXTRACT: A preparation containing the active ingredient of a substance in concentrated form FE Iron

FESO4: Iron sulfate

FISH MEAL: Made from ground fish byproducts and non-food fish, 60-70% protein. A rich source of amino acids

FISH PROTEIN: Concentrated fish meal

GLUTAMINE (L): (Glutamate) An amino acid involved in plant growth. Supplementation may increase stress resistance and growth

GUANO: Seabird or bat poop

HUMIC ACID: A complex of acids that result from the decomposition of plant matter. It contains humic and fulvic acids as well as other molecules. It

JASMONIC ACID: Regulates plant growth and development processes including growth inhibition, senescence, flower development and leaf abscission.

K2CO3: Potassium carbonate, a common fertilizer

KELP: The seaweed, ascophyllum nodosum.

Kh2PO4: Potassium phosphate, a common fertilizer

KhSO4: Potassium hydrogen sulfate (potassium- bisulfate); a common fertilizer

K2O: Potash, a common fertilizer

Kh2PO4: Potassium phosphate, a common fertilizer

KNO3: Potassium nitrate, a common fertilizer

K2SO4: Potassium sulfate, a common fertilizer

K: Potassium, always used as a compound

MGSO4: Magnesium sulfate aka Epsom Salts

MICRONUTRIENTS (MICROS): Elements used by plants in small quantities. They are: boron (B), zinc (Zn), manganese (Mn), iron (Fe), copper (Cu), molybdenum (Mo) and chlorine (Cl). In total, they constitute less than 1% of the dry weight of most plants.

MNSO4: Manganese sulfate- Micro-nutrient helps to regulate the bio-availability of nutrients to the roots.

MOLASSES: Sugar concentrate made from sugarcane

MYCORRHIZAE: Fungi that grow in association with plant roots in a symbiotic relationship. Ectomycorrhizae form a cell-to-cell relationship with the root hairs. Arbuscular mycorrhizae penetrate the root cells. Both provide nutrients and protection in return for root exudate containing their food, sugars.

MG: Magnesium, an essential element

MGHPO4: Magnesium phosphate

N: Nitrogen

P: Phosphorous, Always used as a compound

PHOSPHATES: Phosphorous compounds

PO4: Phosphate

P2O5: Phosphorous pentoxide, commonly used fertilizer

*POTASSIUM SORBATE: Preservative and fungicide commonly used in foods and cosmetics

PHYTO-ACIDS: (Bloom Master, Earth Juice). Undetermined plant products.

RADISH: Ferments into amino acids which are growth stimulators

SAPONINS: Derived from Yucca. Reduce water surface tension and loosens minerals from around roots


SUGAR: Plant food supplement absorbable by roots

TRIACONTINOL: Plant growth stimulator. Large quantities are found in alfalfa.

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