Biochar for Tree Planting & Established Trees
Blend into backfill at planting, or mulch-layer and irrigate existing trees. Improves the structure of the root zone for the life of the tree.
Last updated April 18, 2026
At planting
The single best moment to add biochar is when the root ball goes into the ground. The backfill you make is the pore structure the tree lives in for decades.
- Ratio: 1 part charged biochar to 2 parts native soil (by volume) — about 33 % biochar in the backfill.
- Blend thoroughly before backfilling. Do not concentrate the biochar in a ring around the root ball.
- Water in heavily. The whole planting hole should be saturated once.
- Mulch on top with wood chips; the biochar is integrated in the backfill, not on the surface.
For an established tree
You cannot get biochar to deep roots without digging. But you can:
- Drill-injection: Use a soil auger to bore 30 cm deep holes in a circle at the drip line. Fill each with charged biochar + compost mix. 8–12 holes per tree.
- Mulch ring: Layer biochar 1 cm thick under your usual wood-chip mulch, around the drip-line radius. Water in; the root zone will wick it downward over seasons.
Coverage
Math assumes a 1:2 charged-biochar-to-soil backfill at our measured bulk density of 235 kg/m³. Hole volumes are approximate (diameter × diameter × depth for a cylindrical hole). One 6.5 L bag holds 1.5 kg.
| Application | Biochar |
|---|---|
| New shrub, 45 cm × 30 cm hole (~0.05 m³) | ~17 L / 3.9 kg — three 6.5 L bags |
| New small tree, 60 cm × 45 cm hole (~0.13 m³) | ~43 L / 10 kg — seven 6.5 L bags |
| New medium tree, 80 cm × 60 cm hole (~0.30 m³) | ~100 L / 24 kg — see wholesale for volumes this size |
| Established tree drip-line injection (medium tree, 8–12 holes × ~2 L each) | ~20 L / 4.7 kg — three 6.5 L bags |