# Molasses

> Molasses is a sugar-rich by-product of sugar refining added to soil feeds; its sugars feed soil microbes, not the plant, and do not sweeten buds.

- Canonical: https://genetixbay.com/knowledge/glossary/molasses.html
- Also written: blackstrap molasses, unsulphured molasses, carbs (additive), carbohydrate additive, sugar additive
- Glossary category: Nutrients · Evidence: Myth
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

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](https://genetixbay.com/knowledge/glossary/sulfur.md). Gardeners often add it to soil drenches and [compost teas](https://genetixbay.com/knowledge/glossary/compost-tea.md).

## 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](https://genetixbay.com/knowledge/glossary/photosynthesis.md) and do not take up meaningful sugar through the roots to use as food. In hydro and [coco](https://genetixbay.com/knowledge/glossary/coco-coir.md), 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](https://genetixbay.com/knowledge/mythbusters.md).

## Related terms

[Organic fertiliser](https://genetixbay.com/knowledge/glossary/organic-fertiliser.md), [Biostimulant](https://genetixbay.com/knowledge/glossary/biostimulant.md), [Potassium](https://genetixbay.com/knowledge/glossary/potassium.md), [Humic acid](https://genetixbay.com/knowledge/glossary/humic-acid.md)

## Read more

- [Organic vs mineral nutrition for cannabis: what the trials show](https://genetixbay.com/knowledge/nutrients/organic-vs-mineral.md)
- [Living soil (no-till, water-only organic growing)](https://genetixbay.com/knowledge/systems/living-soil.md)

## Sources

1. Marschner P (ed.). 2012. Marschner's Mineral Nutrition of Higher Plants, 3rd ed. Academic Press. https://doi.org/10.1016/C2009-0-63043-9