Molasses is the thick syrup left after sugar is crystallised from sugar cane or beet. Blackstrap molasses is the most concentrated grade, containing sugars plus some potassium, calcium, magnesium, iron and sulfur. Gardeners often add it to soil drenches and compost teas.
In practice
In soil and compost teas, molasses is a quick food for bacteria and fungi, which can boost microbial activity for a while. That is its real role. Plants make their own sugars by photosynthesis and do not take up meaningful sugar through the roots to use as food. In hydro and coco, sugar feeds unwanted biofilm and can lead to root problems, so keep it out of reservoirs. Use unsulphured grades in soil; sulphured molasses contains a preservative.
Don't confuse with
- Carbohydrate "bloom" additives: often similar sugars in a branded bottle.
- Humic and fulvic acids: organic acids, not sugars.
Myth check
Molasses and sugars feed soil microbes only, not the plant (GenetixBay house position, Evidence: Myth for "molasses sweetens buds" or "feeds the plant"). Flavour comes from genetics, overall health, drying and curing. See Mythbusters.
Sulfur (S) is a secondary nutrient taken up as sulfate, used in the amino acids cysteine and methionine; deficiency yellows new growth fairly evenly.Compost tea is a liquid made by steeping compost or worm castings in water, often aerated with food sources, to extract and multiply microbes for the root zone.The process in chloroplasts that uses light energy to turn carbon dioxide and water into sugars and oxygen; cannabis uses the C3 pathway.Coco coir is a growing medium made from processed coconut husk, prized for holding water and air at once; it binds calcium and magnesium unless buffered.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.Fulvic acid is the small, soluble fraction of humic substances that stays dissolved at any pH and binds metal ions; its benefit in cannabis is largely unproven.An organic fertiliser supplies nutrients from plant, animal or mineral-rock sources that soil microbes must break down into ions before roots can absorb them.A biostimulant is a product claimed to improve plant growth, uptake or stress tolerance by means other than supplying nutrients, such as seaweed extract, humics, amino acids or microbes.Potassium (K) is a mobile macronutrient that controls water balance, stomata and enzyme activity; deficiency scorches the edges of older leaves.Humic acid is a large, dark organic fraction of decomposed matter that binds nutrients and may modestly aid root growth; effects in cannabis are small and inconsistent.
