# Zinc sulfate

> Zinc sulfate (ZnSO4) is the standard soluble zinc salt for micronutrient mixes, about 22.7% Zn as the heptahydrate and 35.5% as the monohydrate.

- Canonical: https://genetixbay.com/knowledge/glossary/zinc-sulfate.html
- Also written: ZnSO4, zinc sulphate, ZnSO4·7H2O, zinc sulfate monohydrate
- 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"

Zinc sulfate is the salt of [zinc](https://genetixbay.com/knowledge/glossary/zinc.md) and [sulfate](https://genetixbay.com/knowledge/glossary/sulfate.md). The two common forms are the heptahydrate (ZnSO4·7H2O, about 22.7% Zn) and the monohydrate (ZnSO4·H2O, about 35.5% Zn). Which one is in the bag changes the dose by more than half again, so read the label.

## In practice

It supplies zinc in DIY [micronutrient](https://genetixbay.com/knowledge/glossary/micronutrient.md) stocks. Plants need only a fraction of a mg/L (ppm) in solution, so the salt is weighed in milligrams or made into a concentrated stock. Like other unchelated metals, it becomes less available as [pH](https://genetixbay.com/knowledge/glossary/ph.md) rises and is tied up by high phosphorus. Overdosing is easy with a kitchen scale; a 0.01 g scale or a [stock solution](https://genetixbay.com/knowledge/glossary/stock-solution.md) is the safe route.

## Units and formula

1 mg/L of the heptahydrate gives about 0.23 mg/L (ppm) Zn; 1 mg/L of the monohydrate gives about 0.36 mg/L Zn.

## Don't confuse with

- **Zinc oxide**: insoluble, used in soil blends and sunscreen, not hydro.
- **Zinc chelate (Zn-EDTA)**: stays soluble at higher pH.

## Related terms

[Zinc](https://genetixbay.com/knowledge/glossary/zinc.md), [Sulfate](https://genetixbay.com/knowledge/glossary/sulfate.md), [Micronutrient](https://genetixbay.com/knowledge/glossary/micronutrient.md), [Stock solution](https://genetixbay.com/knowledge/glossary/stock-solution.md)

## Read more

- [Zinc (Zn) in cannabis: small leaves, margin burn and the phosphorus link](https://genetixbay.com/knowledge/nutrients/zinc.md)
- [Hydroponic salts explained: what each fertiliser salt supplies](https://genetixbay.com/knowledge/nutrients/hydroponic-salts.md)

## Sources

1. Sonneveld C, Voogt W. 2009. Plant Nutrition of Greenhouse Crops. Springer. https://doi.org/10.1007/978-90-481-2532-6