Most articles on trees for poor soil stop at survival. The really useful question is which trees rebuild the soil while they grow.
Five trees that handle poor soils and leave the ground better than they found it.
How trees improve soil
Nitrogen fixing. Wattles and casuarinas form root nodules with nitrogen-fixing bacteria, pumping fertility back into depleted ground. Proteoid roots. Banksias produce specialised root clusters that extract phosphorus from the leanest soils. Mineral cycling. Eucalypts pull deep minerals up the trunk and drop them as leaf litter on the surface.
Coast Banksia
Proteoid roots pull phosphorus from low-nutrient ground. Drops nutrient-rich leaf litter and improves the root zone over time.
Manzanillo Olive
Prefers poor ground. Drops oil-rich leaves and slowly builds organic matter. Lives for centuries on the same patch.
Brittle Gum
Deep roots pull minerals from below and cycle them through leaf drop on the surface.
Weeping Myall
Fixes nitrogen, conditions clay soils and adds long-term fertility to country sites.
River Sheoak
Another nitrogen-fixer, and a serious anchor for poor or compacted soils. Drops a fine soft mulch of needles that builds the topsoil layer.
How to plant on poor soil
Backfill with the existing soil rather than imported compost, so the roots adapt to local conditions. Mulch heavily out to the drip line but leave the trunk collar bare. Water deeply through the first two summers. After that, the trees do the soil work for you.
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