Bonsai Soil — Mixes and Basics

Bonsai Soil Basics (https://www.bonsaiempire.com/basics/bonsai-care/bonsai-soil):

Deciduous tree bonsai soil (winter-hardy broadleaf): 50% Akadama, 25% Pumice, 25% Lava rock.

Coniferous / Pine bonsai soil: 33% Akadama, 33% Pumice (or expanded clay/keramzit and soil), 33% Lava rock.

Japanese Maple: A mix of 30% potting soil, 50% pine bark and 20% perlite drains well and allows air exchange at the roots; avoid adding sand. Alternatively use turface, chicken grit (pure granite without oyster shell) or haydite or lava plus pine fines, mixed 1:1:1. One suggested mix is 70% pumice, 20% Kiryu and 10% pine tree bark for Japanese maples; for other maples (trident, campestris) use akadama instead of Kiryu. Note on bark: all bark slowly decomposes in the pot and depletes nitrogen, so consider whether an organic component is really needed — the only necessary one may be the fertilizer used.

Sakura (cherry): Use loam or potting soil, akadama and some gravel at about a 3:3:2 ratio; cherry trees like water-retaining soil. A better ratio may be 50% Akadama, 25% grit or lava rock and 25% water-retentive organic material (2:1:1), then adjust to local weather.

For seeds: Use a peat pellet, or add more sand to potting soil at a 3:4 ratio. Tray method: (1) Fill the bottom of a tray with a cultivation mix of one part peat and one part perlite. (2) Add a thin layer of grit so the seeds remain visible, then draw uniformly spaced grooves in the grit. (3) Plant the seeds along the grooves, spacing them according to species and seed size. (4) Cover everything with a new layer of gravel, once to twice the size of the seed. (5) Water the tray thoroughly and place it outdoors.