Kiryuzuna Japanese Substrate, 3-6mm, 5L

What kiryuzuna is

Kiryuzuna is a hard, iron-rich volcanic sand from the Kiryu area of Japan. Unlike softer substrates it does not break down in the pot, so a mix containing it keeps draining freely for the whole interval between repots.

Which trees it suits

Conifers. Pines, junipers and other trees that prefer a drier, faster-draining root zone are the traditional use. It is normally blended rather than used on its own: mixed with akadama or Sakadama it adds drainage and weight, with a larger share of kiryuzuna for species that like it driest.

How it compares to akadama

Akadama holds more water and slowly softens over the years; kiryuzuna holds less water and keeps its shape and particle size. Blending the two lets you set how wet or dry the root zone runs. Kiryuzuna is also heavier than akadama, which helps stabilise top-heavy conifers in shallow pots.

How much a repot needs

As a guide, a 20 × 15 × 6 cm pot takes about 2 litres of finished mix and a 30 × 22 × 8 cm pot about 5 litres; the fill table above lists more sizes. Used as a third of a conifer blend, a 5 litre bag makes about 15 litres of mix.