If you buy good compost or bagged soil, your native ground underneath doesn't matter.
Contested
Buying good soil doesn't let you ignore the ground underneath. A thin layer over compacted native soil perches water at the boundary, and roots reach the native soil within a season anyway. Improve your own soil with organic matter over time; if drainage is truly bad, go with a tall raised bed or containers rather than a shallow cap of bagged mix.
What is actually known
Good compost or a bagged mix helps, but a thin cap of it over unimproved ground is not a fix, and in-ground it can make things worse. Water moves poorly across the sharp interface between a fluffy imported layer and compacted native soil below, so it perches at the boundary; and roots reach the native soil within a season, so its drainage and structure still govern how the plant does. Raised beds are more forgiving because the rooting volume is deeper, but they still interact with the ground at their base. The durable answer is to improve the native soil with organic matter over time — and where drainage is genuinely bad, a tall raised bed or containers with a consistent mix, not a shallow layer of good soil over bad.
Evidence: not yet confirmed against its 1 source.
what this rests on - one pointer
a texture interface between an imported layer and compacted native soil perches water and impedes root and water movement across the boundary; roots reach native soil within a season; extension consensus on soil improvement vs layering
When would that grow at your place? →
Cite this page
Milpa Gardens. "If you buy good compost or bagged soil, your native ground underneath doesn't matter." Evidence grade: Contested. https://milpa.garden/beliefs/bagged-soil-topsoil-top/
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