Keeping mint under control in the garden

Why mint is so troublesome

Mint is a blessing and a curse. The plant grows unchecked and appears everywhere you do not want it. A single root breaks into a hundred pieces, and each piece immediately grows into a new plant. Within three years you have turned a modest mint into a wild jungle that takes over your entire border. This article teaches you how to keep mint enjoyable without digging it out.

The key is containment. Mint has no problem with poisonous soil compounds, no problem with any soil, no pests that interest it, and no diseases. It just wants to grow. You cannot kill it through neglect, and you cannot control it without a plan. Fortunately there are four ways.

Burying a root barrier: the reliable method

This is the recipe gardeners use everywhere. You bury a pot. Not just any small pot: use a sturdy bucket or planter at least 30 cm deep and 30 to 40 cm across, with no drainage hole at the bottom. The mint grows inside that pot, and its underground roots cannot escape.

Here is how you do it. In spring (April or May) prepare your mint plant. If it is old and tangled, divide it with a spade: just cut it in two pieces. Plant each piece in a pot at least 30 cm deep with good potting soil. Water until it settles well. Place it in a sheltered spot with at least 4 hours of sun a day (mint can also tolerate partial shade, but then grows more slowly and less full).

Now dig a larger hole in the ground: large enough for that pot, so the rim sticks out at least 5 cm above the ground. This matters, because mint spreads not only through underground roots but also through surface runners that can creep over a low rim and root outside the pot. Bury the pot itself in the ground, with the mint inside it. Fill the hole back in around it with soil.

Now the mint grows mainly in that pot. Check two or three times during the growing season for runners creeping over the rim, and snip them off straight away. Harvest by simply cutting the stems. Water once a week in full summer, twice a week in spring.

After two to three years the pot is completely packed with roots. Then you dig it out, divide the rootball into two or three pieces, and replant it. Or you enjoy that it grows less wildly because its roots compete with each other. Want to see your mint ahead of time in a garden design? Visit gardenworld.app and see how your mint grows together with other herbs.

Which mint varieties: the less wild-growing ones

Not all mints are equally invasive. Some varieties grow much more carefully and are therefore better for planting in the ground.

Mentha suaveolens (Apple mint or pineapple mint): grows more calmly than most, has a fruity apple or pineapple scent, with coarse, felty leaves. Good for the open ground if you do not want to dig it out every week.

Mentha spicata (Spearmint or garden mint): the classic kitchen mint found in most Belgian and Dutch gardens. Still spreads, but a bit more manageable than peppermint. Flowers white to pale purple in July and August.

Mentha pulegium (Pennyroyal): stays low, around 20 to 30 cm, with small narrow leaves and a sharp smell. A safety note: pennyroyal naturally contains a lot of pulegone, a compound that is toxic in larger amounts for people and pets. Never use it for tea or cooking, and keep it out of reach of children and animals. As a non-edible groundcover in a closed pot, purely for the scent, it can work.

Mentha aquatica (Water mint): belongs naturally in wet, boggy soil, where it spreads just as eagerly as other mints. Only plant it in a pond edge or bog corner with its own barrier, never loose in an ordinary border.

Mentha x piperita (Peppermint): very aromatic, the strongest flavour of all the mints. Grows extremely wild. Only in a pot or with a solid root barrier.

Chocolate mint (Mentha x piperita 'Chocolate'): a peppermint cultivar with a soft cocoa scent, lovely with tea or dessert. It spreads just as enthusiastically as ordinary peppermint, so it also belongs only in a pot.

Harvesting: when and how

You can harvest mint from May onwards, as soon as you have enough leaf. For fresh eating pinch off the top 10 cm of the stem, just above a leaf pair. This encourages the plant to branch more and gives you bushier plants.

For drying do this better in full summer (June, July, August) when the essential oils are strongest. Cut a bundle of stems (about one third of the plant), and tie them loosely with twine. Hang them upside down in a dry, warm place with air movement. This can be in the garden under a shelter, in a shed, or indoors above a radiator. The mint is dry when the leaves feel crispy (this usually takes 10-14 days).

If you want to pick fresh until autumn, reverse this: harvest lightly in June, July, August, and pick only what you need in September and October. Do not let the plant flower if you want fresh: as soon as you see the flower buds, cut everything off.

Step by step

Step 1: Choose your mint variety and pot

Choose apple mint (calmer) or spearmint (somewhat wilder). Get a pot or bucket at least 30 cm deep, with no drainage hole.

Step 2: Fill the pot with potting soil

Fill the pot about three-quarters full with good potting soil. Put your mint plant in. Water until moist.

Step 3: Dig a hole

Dig a hole in your border exactly the size of your pot. Choose full sun or partial shade. Place the pot in the hole so the rim sticks up at least 5 cm above the ground.

Step 4: Fill in and water

Fill the hole around the pot with soil. Water. Done.

Step 5: Harvest regularly and check for runners

From June, pick regularly and check that no runners are creeping over the rim of the pot. Snip them off at once. This stimulates the mint and keeps it inside its boundaries.

Step 6: Dry in full summer

In July-August harvest for drying: cut stems, hang upside down, wait 2 weeks. Rub off leaves and store.

Step 7: Refresh after three years

After three years the pot is full of roots. Then dig it out, divide it into pieces, and replant.

Frequently asked questions

Can I just plant mint in the ground without a pot?

Absolutely not. After a year you will have mint everywhere. Always use a root barrier or pot.

How do I get mint out of my border that is already everywhere?

This is a job of months. Dig as deep as possible and remove every root piece. Do this three times a week. Let the hole lie fallow for three months and dig out what grows back again. With persistence it works.

Can I grow mint indoors in a pot?

Yes, but mint wants to grow outside. Indoors on a sunny window works, but it becomes thin and tall. Better outside in a pot.

Is mint limited by frost in winter?

No. Mint is hardy to below minus 10 degrees. The above-ground parts die back in autumn, but the roots sleep. Next spring everything grows again.

Cats and mint

Many cats respond to mint, but it is catnip (Nepeta cataria) that really sends them wild, thanks to a compound called nepetalactone. Ordinary mint (Mentha) usually smells pleasant to cats too, but attracts them less strongly. If your cats like to roll through the border, plant your mint pot somewhere they cannot reach, or accept that the plant gets flattened now and then. Some gardeners grow a separate pot of mint or catnip just for their cat.

The benefits of dried mint

Dried mint is as good for the kitchen as fresh, and keeps for months. A small handful of dried leaves tastes as strong as a much bigger handful of fresh ones. This saves a lot of picking in winter. Put your dried mint in a glass jar in a dark spot in your kitchen, and you have tea until March.

Common mistakes

Too much water in the pot: Mint holds plenty of water, but not constantly wet. Water once a week in normal summer, not every day.

Pot in shade: Mint grows in shade, but much slower and thinner. Full sun is better.

Not cutting stems: If you let the mint grow without harvesting, it secretly becomes woody and thin-leaved. Regular harvesting keeps it thick.

After drying not stored properly: Dried mint quickly loses its aroma in the light. Store dark and dry.

See it in your own garden first

Not sure if mint fits well into your garden plan? On gardenworld.app you can see it first in a design of your own garden. Upload a photo of your spot, view a free preview with mint and other herbs next to it, and check that it all works together. The sharp image with a full plant list costs 7.99 euros, once only, no subscription.