# Iron chelate

> An iron chelate is iron bound to an organic molecule (EDTA, DTPA or EDDHA) that keeps it dissolved and available; each type holds up to a different pH.

- Canonical: https://genetixbay.com/knowledge/glossary/iron-chelate.html
- Also written: chelated iron, Fe chelate, Fe-EDTA, Fe-DTPA, Fe-EDDHA, iron EDTA
- 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"

An iron chelate is ferric iron held in a ring-like organic molecule, the [chelating agent](https://genetixbay.com/knowledge/glossary/chelate.md), which stops it from forming insoluble hydroxides. The three common types are Fe-EDTA (about 13% Fe), Fe-DTPA (about 10-11% Fe) and Fe-EDDHA (about 6% Fe). They differ mainly in how high a [pH](https://genetixbay.com/knowledge/glossary/ph.md) they survive.

## In practice

Fe-EDTA works well up to about pH 6.0-6.5, fine for most hydro but weak in high-pH soil or water. Fe-DTPA holds to about pH 7.0-7.5 and is the usual choice for [coco](https://genetixbay.com/knowledge/glossary/coco-coir.md) and hydro. Fe-EDDHA stays effective to pH 9 or more and is used for alkaline soils; it stains solutions dark red. [EDTA](https://genetixbay.com/knowledge/glossary/edta.md) iron also breaks down in strong light, so opaque reservoirs help. Feeds typically target about 1-3 mg/L (ppm) Fe.

## Don't confuse with

- **Iron sulfate**: unchelated iron, precipitates quickly above pH 6.
- **Iron oxide or rust**: insoluble and unavailable to roots.
- **Amino acid chelates**: weaker, less stable bonding, different behaviour in solution.

## Related terms

[Iron](https://genetixbay.com/knowledge/glossary/iron.md), [Chelate](https://genetixbay.com/knowledge/glossary/chelate.md), [EDTA](https://genetixbay.com/knowledge/glossary/edta.md), [DTPA](https://genetixbay.com/knowledge/glossary/dtpa.md), [EDDHA](https://genetixbay.com/knowledge/glossary/eddha.md)

## Read more

- [Iron (Fe) in cannabis: yellow new growth, chelates and pH](https://genetixbay.com/knowledge/nutrients/iron.md)
- [Hydroponic salts explained: what each fertiliser salt supplies](https://genetixbay.com/knowledge/nutrients/hydroponic-salts.md)

## Sources

1. HortScience. 2025. Iron chelates (Fe-EDTA, Fe-DTPA, Fe-EDDHA) in high-pH soilless media. HortScience 60(3):404. https://journals.ashs.org/view/journals/hortsci/60/3/article-p404.xml
2. Sonneveld C, Voogt W. 2009. Plant Nutrition of Greenhouse Crops. Springer. https://doi.org/10.1007/978-90-481-2532-6