# Boron

> Boron (B) is a micronutrient needed for cell-wall structure and growing tips; the gap between deficient and toxic levels is narrow.

- Canonical: https://genetixbay.com/knowledge/glossary/boron.html
- Also written: B, borate, boron deficiency, boron toxicity
- 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"

Boron is a [micronutrient](https://genetixbay.com/knowledge/glossary/micronutrient.md) taken up mainly as uncharged [boric acid](https://genetixbay.com/knowledge/glossary/boric-acid.md). It cross-links pectins in cell walls and is needed wherever cells are dividing and expanding: [shoot tips](https://genetixbay.com/knowledge/glossary/apical-meristem.md), root tips and developing flowers. In cannabis it is largely immobile.

## In practice

[Deficiency](https://genetixbay.com/knowledge/glossary/nutrient-deficiency.md) kills or deforms growing points: brittle, thickened or hollow stems, distorted new leaves and dying tips. It can look like [calcium deficiency](https://genetixbay.com/knowledge/glossary/calcium.md). Toxicity shows as yellowing and burning of older leaf margins. The safe window is narrow, so hydro feeds use small amounts, usually about 0.2-0.5 mg/L (ppm) B, typically from boric acid or a borate. Some tap and [well waters](https://genetixbay.com/knowledge/glossary/tap-water.md) carry enough boron to matter; check the water report.

## Don't confuse with

- **Calcium deficiency**: similar new-growth symptoms; check [pH](https://genetixbay.com/knowledge/glossary/ph.md), humidity and the feed for both.
- **Borax or boric acid as insecticide**: a different use at very different concentrations.
- **Potassium deficiency**: margin burn on older leaves but with a different pattern and history.

## Myth check

"A pinch of borax" is a risky home fix. With a narrow margin, measure grams per litre, not pinches. See [boron](https://genetixbay.com/knowledge/nutrients/boron.md).

## Related terms

[Micronutrient](https://genetixbay.com/knowledge/glossary/micronutrient.md), [Immobile nutrient](https://genetixbay.com/knowledge/glossary/immobile-nutrient.md), [Boric acid](https://genetixbay.com/knowledge/glossary/boric-acid.md), [Calcium](https://genetixbay.com/knowledge/glossary/calcium.md), [Nutrient toxicity](https://genetixbay.com/knowledge/glossary/nutrient-toxicity.md)

## Read more

- [Boron (B) in cannabis: distorted tips, dying roots and a narrow safe window](https://genetixbay.com/knowledge/nutrients/boron.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
2. Cockson P, Landis H, Smith T, Hicks K, Whipker BE. 2019. Characterization of nutrient disorders of Cannabis sativa. Applied Sciences 9(20):4432. https://doi.org/10.3390/app9204432