A bloom booster is a supplement, usually high in phosphorus and potassium and often based on monopotassium phosphate, sold to be added to a base feed during flowering. Labels such as 0-50-30 or "PK 13-14" are typical. Some products also contain sugars, amino acids or plant extracts.
In practice
A complete base feed already supplies enough phosphorus for flowering cannabis. Independent trials by Shiponi and Bernstein, Westmoreland and Bugbee, and Hershkowitz, Westmoreland and Bugbee found yield and cannabinoids plateau at moderate root-zone P, roughly 25-60 mg/L (ppm). Above that, extra P mostly leaves in the runoff, and can tie up zinc, iron and copper. Excess K from the same bottle can suppress calcium and magnesium.
Don't confuse with
- Bloom base: a complete flowering feed, not an add-on.
- Plant growth regulators: some historic "boosters" contained them; a separate concern.
Myth check
"More phosphorus in flower means bigger buds" is not supported: there is a plateau (Evidence: Established; GenetixBay house position agrees with the trials). See bloom boosters and Mythbusters.
Monopotassium phosphate (MKP, KH2PO4) supplies about 22.7% phosphorus and 28.7% potassium with no nitrogen, and is the base of most PK boosters.A cannabinoid is any compound that binds the body's cannabinoid receptors or shares the typical cannabis terpenophenolic structure; the plant-made ones are phytocannabinoids such as THCA and CBDA.Runoff is the water or nutrient solution that drains out of the bottom of a container after irrigation; growers test it to see what is happening in the root zone.Zinc (Zn) is a micronutrient needed for auxin production and many enzymes; deficiency gives small, twisted new leaves and shortened internodes.Copper (Cu) is a micronutrient used in photosynthetic electron transport and lignin formation; plants need only traces, and excess is toxic to roots.The reproductive phase of the cannabis life cycle, from the switch to flowering until harvest, during which the plant stretches, builds buds and ripens resin.Phosphorus (P) is a mobile macronutrient used in energy transfer (ATP), DNA and cell membranes; cannabis needs moderate amounts and gains nothing from excess.The N-P-K ratio is the three numbers on a fertiliser label giving percent nitrogen, phosphate (P2O5) and potash (K2O) by weight, not elemental P and K.Nutrient antagonism is when an excess of one element reduces the uptake or use of another, such as high potassium suppressing magnesium and calcium.A feed chart is a manufacturer's or grower's schedule of nutrient doses by week or stage; treat it as a ceiling to test against, not a rule.
