# Cobalt

> Cobalt (Co) is not essential for cannabis; it is needed by nitrogen-fixing bacteria in legume nodules, so it appears only as a trace in some feeds.

- Canonical: https://genetixbay.com/knowledge/glossary/cobalt.html
- Also written: Co, Co2+, cobalt nutrient
- Glossary category: Nutrients · Evidence: Established
- 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"

Cobalt is not an essential element for higher plants. It is required for vitamin B12 and by the bacteria that fix nitrogen in legume root nodules, which is why it is sometimes listed as "beneficial". Cannabis does not form those nodules and has no known requirement for cobalt.

## In practice

Some fertiliser blends and [micronutrient](https://genetixbay.com/knowledge/glossary/micronutrient.md) premixes contain trace cobalt, mostly as a carry-over from formulas designed for legumes and other crops. Growers should neither add it nor worry about its absence. At higher concentrations cobalt is toxic and can interfere with iron uptake, causing [chlorosis](https://genetixbay.com/knowledge/glossary/chlorosis.md) on new growth. If a label lists cobalt, the amount should be tiny, well below 0.1 mg/L (ppm) in the final solution.

## Don't confuse with

- **Copper (Cu)**: an essential micronutrient; easy to confuse by symbol.
- **Molybdenum**: essential for [nitrate](https://genetixbay.com/knowledge/glossary/nitrate.md) reduction; also needed by nitrogen-fixing bacteria.
- **Nickel**: essential in trace amounts for urease.

## Related terms

[Micronutrient](https://genetixbay.com/knowledge/glossary/micronutrient.md), [Beneficial element](https://genetixbay.com/knowledge/glossary/beneficial-element.md), [Nickel](https://genetixbay.com/knowledge/glossary/nickel.md), [Molybdenum](https://genetixbay.com/knowledge/glossary/molybdenum.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