Living mulch suppresses weeds and conserves soil moisture.
A good hunch · suboptimal if ignored → advise
How it works
A living cover keeps a leaf canopy over the ground: it intercepts light at the soil surface, so weed seedlings are shaded out before they establish, and it slows surface evaporation, so the soil holds more water. In a Three Sisters planting this is the squash's role — its broad leaves shade the bed.
The evidence
Evidence: confirmed against 2 sources in the research-based literature.
the 2 sources
UMN Extension, 'Mulching for soil and garden health', extension.umn.edu/managing-soil-and-nutrients/mulching-soil-and-garden-health (read 2026-07-11): mulch 'Suppresses weeds'; 'Studies show that mulch reduces evaporation from the soil surface and helps soil hold water.'
Cornell Cooperative Extension (Warren Co. Master Gardener), 'Creating a Three Sisters Garden', warren.cce.cornell.edu/gardening-landscape/warren-county-master-gardener-articles/creating-a-three-sisters-garden (read 2026-07-11): 'The large, prickly squash leaves shade the soil, preventing weed growth' — the living-mulch role in Three Sisters.
Change history
Every change to this rule is one commit. This is what the project's version history records — the date and the reason — not a summary of it.
- living mulch — fill the stub mechanism from its own sources
- promote to verified — living mulch suppresses weeds and conserves moisture
- cite UMN mulch + Cornell Three Sisters for living mulch (rule confirmed)
Cite this page
Milpa Gardens. "Living mulch suppresses weeds and conserves soil moisture." Evidence grade: A good hunch. https://milpa.garden/rules/living-mulch-suppresses-weeds-conserves-soil-moisture/
A garden-planning corpus: every claim states its evidence grade and links its sources on the page. Cite it with the grade, and add the date you read it.