Bonsai soil & pots
Soil is the cheapest thing a beginner can get right and the most common thing they get wrong. A bonsai lives in a shallow pot with very little soil, so the soil has to drain fast enough that roots are never sitting in water, while still holding some moisture and air. Ordinary potting soil cannot do both. This silo decodes the components — akadama, pumice, lava — explains particle size, and shows how to adjust a mix by species, then points you to the bags worth buying.
Why bonsai soil is not potting soil
Potting soil is designed for deep pots and plants that like steady moisture. It holds a lot of water, packs down over time, and chokes off the air around the roots. In a shallow bonsai pot that means roots sit wet, run out of oxygen, and rot. The frustrating part is that a tree can look fine for weeks before it collapses from root rot you never saw coming. Switching to a gritty, fast-draining bonsai mix removes that risk, and it is the single highest-leverage thing a beginner can do after choosing the right species.
Particle size and why it matters
Bonsai soil is built from hard particles roughly 2–6 mm across, sifted to remove dust and fines. The gaps between those particles are where air and drainage live. Too small and the mix packs down and holds water like potting soil; too large and it dries out too fast and holds no nutrients. A good bag is already sifted to a useful range. If you mix your own, sifting out the dust is the step beginners skip and regret — un-sifted fines clog the air gaps and undo the whole point.
The three components
Akadama — the water-and-nutrient holder
Akadama is a fired Japanese clay that holds water and nutrients, then breaks down slowly over a couple of years — which conveniently signals when a tree is due for repotting. It is the traditional backbone of a bonsai mix. It costs more than the alternatives and softens with age, which is why many growers blend it with harder, stable components rather than using it alone.
Pumice — the light, airy stabiliser
Pumice is a light volcanic rock that holds some water and keeps the mix open and airy. It is cheap, stable, and does not break down, so it holds the structure of the mix together as the akadama ages. A reliable workhorse component.
Lava rock — the structure and drainage
Lava rock adds structure and free drainage, holds a little water on its rough surface, and never breaks down. It keeps the mix from collapsing and helps water move through quickly. Together, akadama, pumice and lava cover water retention, aeration and drainage — which is why the classic blend uses all three.
Mixing by species
A common all-purpose beginner blend is roughly equal parts akadama, pumice and lava. From there you adjust toward what the tree wants:
- Thirsty deciduous trees (maples, elms) — lean more akadama for extra water retention.
- Conifers (junipers, pines) — lean more pumice and lava for faster drainage, since they dislike wet feet.
- Tropical and indoor trees (ficus, jade) — a free-draining mix works well; a small share of an organic component can help hold moisture indoors.
You do not have to mix your own to start. A good pre-mixed bag is sifted and balanced for general use, and the best bonsai soil guide compares them.
A word on pots
Whatever pot you use, it needs drainage holes — the fast-draining soil only works if water can leave. A plain training pot is fine while a tree is in development; the showy glazed ceramic is for a tree you are finished styling. Shallow pots dry faster than deep ones, which is one more reason to water by feel rather than on a schedule. Dedicated pot buyer guides land in a later batch.
Featured guides
The current published guides in this silo. More land each batch.
Landing next: akadama buyer guide, a bonsai pots guide, and kanuma soil for acid-loving species like azalea.
Soil for your situation
If you just want a bag that works
Buy a pre-mixed, sifted bonsai soil rather than mixing your own at first. It removes the guesswork while you learn how often your tree dries out. See the best bonsai soil guide.
If you are growing indoors
Indoor air and lower light mean a mix dries more slowly, so a free-draining blend is even more important to avoid soggy roots. Pair the right soil with enough light — sometimes a grow light — and an indoor tropical does well.
If you want to mix your own
Start from equal parts akadama, pumice and lava, sift out the dust, and adjust toward the species. The soil guide covers the components to buy by the bag.