Keep mint contained. Planted loose in a bed, it takes over
As recorded: Mint spreads aggressively by underground rhizomes and will colonize a bed, out-competing and crowding its neighbors if grown loose in open ground. Do not plant it directly in a shared bed. Contain it in a pot, or in a bottomless container sunk into the ground, and harvest and pull strays to keep it in bounds.
Promising A person has checked it against its sources. If you skip this, it still grows, just less well. The planner suggests it.
How it works
Rhizomatous, and stoloniferous, spread. Mint's horizontal underground stems (rhizomes) and its surface runners root at their nodes and send up new shoots, so an unconfined plant expands outward from the crown each season and reappears wherever a node reaches soil. This vegetative creep is why a loose planting takes over a bed, and why the control is a physical soil barrier. Spacing does not contain it.
What to do about it
Grow mint in a container above ground, or plant it in a large bottomless pot or buried edging sunk into the bed (roughly 3-4 inches proud of the soil and 10-15 inches below), so escaping rhizomes are forced up over the lip where they show. Cut back and harvest through the season, and pull any runner that clears the barrier before it roots.
How much it matters: No reliable magnitude is stated or estimated. Left unconfined in open ground mint spreads through the bed over a season and crowds its neighbors; contained in a pot or a sunken barrier it stays put. Because keeping it contained is a cultural practice the gardener performs, the rule only advises.
The evidence
Evidence: checked against 2 sources in the research-based literature.
The 2 sources
They grow from 1-3 feet tall and aggressively spread by underground rhizomes
Mint spreads quickly in open garden areas and will out-compete most garden plants
Plants it applies to
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How this rule has changed
Every change is dated, newest first. The full record, with each reason, is in the data download.
- Wording made clearer
- Wording made clearer
- Added to the rules
Cite this page
Milpa Gardens. "Keep mint contained. Planted loose in a bed, it takes over." Evidence grade: Promising. https://milpa.garden/rules/mint-spreads-aggressively-underground-rhizomes-will-colonize/
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- Well established
- The rule names its mechanism and is settled, by sources a person has read and checked or by plain arithmetic and geometry.
- Promising
- The mechanism is named and the literature backs it. A few questions are still open.
- A good hunch
- Plausible by its mechanism, but field studies are thin, so treat it as a lean.
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- The evidence points both ways, or no study has tested it, so the planner does not enforce it.
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