How do I stop mint taking over the garden?
How mint spreads, the containment that actually works, and how to remove it from a bed it has already colonised.
- Difficulty
- beginner
- Time
- 45 min
- Read
- 3 min
Short answer
Mint spreads by runners just below the surface. Grow it in a pot — either freestanding or sunk into the bed with its rim standing 50mm proud — and repot it every couple of years. Once it is loose in a border, removing every fragment of root is the only way out.
Mint is not invasive by accident. Its runners travel horizontally at shallow depth and every fragment left behind regrows, which is why digging it out half-heartedly makes the problem worse rather than better.
What you'll need
- Large pot or bucket
- Spade
- Fork
- Cardboard and mulch (optional)
Step by step
- Grow it in a container by default.A 30cm pot or a bucket with drainage holes drilled in it. This is the standard answer and there is no good reason to plant mint loose in a bed.
- Sink the pot if you want it to look planted.Bury the pot in the border but leave the rim standing at least 50mm above soil level. Runners escape over a flush rim within a season.
- Check the pot each spring.Runners find the drainage holes and escape into the ground beneath. Lift and check the base annually.
- Repot or divide every two years.Mint exhausts its compost and the centre of the clump becomes woody and unproductive. Split it, keep the young outer pieces and replant in fresh compost.
- Keep different mints apart.Mints hybridise readily and a vigorous one will simply outgrow a delicate one in the same pot. One variety per container.
- Dig out an established patch thoroughly.Fork the whole area over, sifting out every white runner. Any fragment left will regrow, so this needs doing properly once rather than roughly three times.
- Follow up for a full season.Whatever you missed will show itself over the following months. Pull or dig each shoot as it appears, and the patch is exhausted within a year.
- Exclude light where digging is impractical.Thick cardboard and a deep mulch, or heavy light-excluding sheeting, left in place for a full growing season kills it without digging.
- Do not rotavate it.Rotavating chops the runners into hundreds of fragments and each one grows. It is the most reliable way to turn a small patch into a large one.
- Cut it back hard in midsummer.Mint gets leggy and flowers by July. Cutting the whole plant to about 50mm gives a fresh flush of good leaves for late summer.
Tips
- Sink the pot with the rim standing proud. Flush with the soil and it escapes in one season.
- Never rotavate mint — you multiply it.
- Cut it right back in midsummer for a second flush of good leaves.
Common mistakes
- Planting mint directly into a border because the spot looks contained — Runners travel under paths, under edging and through gravel. Within three years it will be in the lawn and among the neighbouring plants.
- Digging out most of the roots and calling it done — Every fragment regrows. Half-clearing a patch spreads it further, because you have loosened and distributed the runners.
If it doesn't work
Mint appearing across the whole border
Cause: Runners spreading underground — Fix: Fork the area over and sift out every white runner, then follow up on regrowth for a full season.
Escaped from a sunk pot
Cause: Rim flush with soil, or runners through the drainage holes — Fix: Lift the pot, remove escaped runners, and reset with the rim 50mm proud.
Sparse woody growth in a pot
Cause: Exhausted compost and a congested crown — Fix: Divide, keep the young outer pieces, and repot into fresh compost.
Mint gone leggy and flowering
Cause: Midsummer — Fix: Cut the whole plant back to about 50mm and water. Fresh growth follows within a fortnight.
Questions people ask
Can I plant mint in the ground at all?
Only inside a sunk container with the rim standing above soil level, or in a bed physically enclosed on all sides and underneath. Anywhere else it will spread.
How do I get rid of mint that has spread?
Fork the area through and remove every white runner, then pull regrowth as it appears for a full season. Alternatively exclude light with cardboard and deep mulch for a growing season.
Why has my mint stopped producing good leaves?
Exhausted compost or a congested woody crown. Divide it every couple of years, keeping the vigorous outer growth, and cut the plant hard back in midsummer.