---
title: Horticultural charcoal in a terrarium | Glass Jar Garden
description: Horticultural charcoal: Chunky wood charcoal that keeps the soil fresh for decades. In the jar it has holds water 25 % by volume, pore space 72.5 % by...
url: https://glassjar.garden/guide/soils/horticultural-charcoal/
---

Soils and layers

# Horticultural charcoal

Chunky wood charcoal that keeps the soil fresh for decades.

## What the simulation uses

- Holds water: 25 % by volume (Water it keeps after draining; the rest runs down to the drainage.)

- Pore space: 72.5 % by volume (Room for air and water between grains; low means roots suffocate when wet.)

- Weight: 360 g/L (How heavy a litre is.)

- pH: 7 to 10 pH (How acid it keeps the soil.)

- Mould risk: none (How much fresh food it gives white mould; high-risk soils fuzz over in the first weeks.)

- Breaks down in: 100 to 1000 years (How long it lasts before rotting down to fine soil.)

- Nutrients: low (Plant food it brings.)

- Presses down to: 97 % of its loose depth (How far pressing can pack it, keeping its weight.)

## Description
Unlike activated charcoal, these are plain wood charcoal chunks. Mixed into soil they add structure and gentle filtering, and fresh pieces raise pH slightly. They will outlast everything else in the jar by centuries.

Also called lump charcoal, biochar, orchid charcoal.

Estimated, where sources were thin: CEC develops only after ageing; water holding estimated.

## Sources

- [en.wikipedia.org/wiki/Biochar](https://en.wikipedia.org/wiki/Biochar)
- [engineeringtoolbox.com/density-materials-d_1652.html](https://www.engineeringtoolbox.com/density-materials-d_1652.html)
- [engineeringtoolbox.com/density-solids-d_1265.html](https://www.engineeringtoolbox.com/density-solids-d_1265.html)

[Grow it in a jar](https://glassjar.garden/?guide=soils/horticultural-charcoal)

[Fine clay pebbles](https://glassjar.garden/guide/soils/clay-pebbles-fine/) · [Horticultural sand](https://glassjar.garden/guide/soils/horticultural-sand/) · [All soils and layers](https://glassjar.garden/guide/soils/)