Akadama Ibaraki Hard Quality 5/10 mm grain - 10 litre pack

What it is and where it comes from

Akadama is a volcanic soil quarried in Japan, here in the Ibaraki selection in "Hard Quality" grade. The granules are clayey, porous and ochre in colour, and arrive fully sterilised. Made in Japan.

The Hard Quality designation indicates the most compact fraction: it is the one that does not break down in water and produces no sludge, so much so that akadama soil is also used for aquarium substrates.

How it behaves in the pot

The granule absorbs water and releases it slowly to the roots, while the excess drains away and leaves air-filled spaces between one piece and the next. It is this twofold behaviour, retention inside the granule and drainage outside, that makes akadama the benchmark bonsai substrate: roots run into it, branch out finely and never sit in the wet.

The critical point of any akadama is how it holds up over time. Soft grades turn to paste after just a few winters and the pot seals up. The hard selection copes far better with frost and watering, keeping the grain recognisable until the next repotting. If you are looking for akadama because your old one turned to mush, that is the difference that matters.

Features

• Japanese volcanic soil (akadama)
• Grade: Hard Quality
• Origin: Ibaraki, Japan - Made in Japan
• Average grain size: 5/10 mm
• 10 litre pack
• Sterilised product
• Can be used pure or mixed with other soils
• Also suitable for aquarium substrates: it does not break down in water

Which grain and for which plants

The 5/10 mm is a medium-coarse grain. It is at home in medium and large pots, on growing specimens and during thickening stages, where you need an airy substrate that will not compact under its own weight. On shohin and shallow pots it is too coarse: a finer fraction is the better choice there.

As an akadama soil it suits most bonsai species, both broadleaves and conifers. On conifers many prefer to lighten it with pumice or lava rock; for acid-loving plants such as azaleas and rhododendrons kanuma remains the correct choice. This grain also works well as a simple drainage layer at the bottom of deep pots.

How to use it when repotting

First of all, sieve it. Even in a hard quality some dust forms during transport, and that dust is what clogs the pores of the pot: it must be removed. Then cover the base, settle the plant in place and work the substrate down between the roots with a chopstick, without pressing it with your thumb.

After repotting, water thoroughly until the water runs clear from the drainage holes. Akadama changes colour when saturated and lightens as it dries: it is the simplest way to know when to water again.

Frequently asked questions

What is akadama and why is it used for bonsai?

It is a Japanese volcanic soil with porous granules. It is used because it combines two things that are hard to find in the same substrate: it holds the water needed inside the granule and lets the excess drain away, keeping the roots oxygenated. It also enriches the substrate with minerals.

Does Hard Quality break down like ordinary akadama?

No, that is its main feature. The hard selection withstands frost and repeated watering while keeping the granule intact, instead of collapsing into suffocating clay. The clearest proof is its use in aquarium substrates, where it stays submerged and creates no sludge.

Can I use this akadama pure?

Yes, medium akadama can be used pure or mixed with other soils and free-draining components such as pumice and lava rock. The choice depends on the species, the climate and the depth of the pot: in rainy areas it is best to lighten it, in hot, dry climates it works well on its own.

What is included

• 1 pack of 10 litres of Ibaraki Hard Quality akadama
• Medium 5/10 mm grain size, sterilised product

If you prefer to measure out the components yourself, you can put together your own mix on the made-to-measure soil page.