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 few inches of good mix over poor soil keeps roots in that thin layer, so plants need more watering and feeding. Work amendments into your soil. Don't just lay them on top, and in shallow raised beds mix in the ground below.

What is actually known

Good compost or a bagged mix helps, but a thin layer of it over poor ground is not a fix. With a few inches of good soil on top, roots stay mostly in that layer, which shrinks the soil they draw water and nutrients from and means more watering and feeding. Plants do best in deep soil that is similar in texture throughout, so amendments need to be mixed down into the soil, and a raised bed shallower than 18 inches should have the original soil mixed in. Over time, roots grow down into the native soil and organic matter improves it. (For permanent plantings such as trees and shrubs the advice differs. There, topdress with mulch and don't dig amendments in.)

The evidence

Evidence: checked against 3 sources in the research-based literature.

The 3 sources

ndsu.edu Read by a person on September 24, 2026

Evaluating, Preparing and Amending Lawn and Garden Soil NDSU Extension

Plants develop better in deep, homogenous soil layers that are similar in texture

extension.umd.edu Read by a person on September 24, 2026

Soil to Fill Raised Beds University of Maryland Extension

Plant roots will grow through the decomposing turf and weeds into the underlying soil

s3.wp.wsu.edu Read by a person on September 24, 2026

The Myth of Soil Amendments, Part III Washington State University Extension, Linda Chalker-Scott

Do not incorporate organic amendments into landscapes destined for permanent installations; topdress with mulch instead

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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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