Akadama
Also known as Red ball earth, Akadama clay
In short
Akadama is a granular volcanic clay mined in Japan, used mainly in bonsai soil. It holds water and air well and darkens when wet, which helps judge when to water, but it gradually breaks down into mud.
How it looks
Rounded, reddish-brown to orange granules that turn noticeably darker when wet. Sold in sizes such as shohin (under 1/16 inch, about 1.6 mm), small (about 1.6–6 mm) and medium (about 6–13 mm). Its composition is mainly silica and aluminium oxide with some iron oxide.
Signs
Breaking down: granules crumble into fine silt that clogs the pot and slows drainage. Colour change from light (dry) to dark (wet) shows moisture at the surface.
What favours it
Akadama has a pH of about 6.9. Harder, higher-quality grades hold their structure longer; softer grades disintegrate sooner, especially when kept wet.
Prevention
- Sieve out dust before use.
- Mix with harder materials such as pumice or lava rock to keep drainage open as the akadama ages.
- Choose harder grades where available.
Treatment
Start with the first step and move down only if the problem persists.
- Repot when the mix has broken down and drains slowly.
Pros and cons
Pros
- Holds water and air while draining freely.
- Changes colour when wet, making watering easier to judge.
- Roughly neutral pH; small grades suit cacti and succulents.
Cons
- Breaks down over time, so repotting is needed.
- Mined in Japan, so elsewhere it is an imported product.
- Lower-quality grades disintegrate quickly in wet conditions.
Look-alikes
Typical uses
Bonsai of most kinds; also cacti, succulents and other container plants that need a free-draining mineral mix.
Related
Sources
Written in our own words from these sources. Check a product label before using any treatment.