How to Stop Mint Taking Over the Garden

Decide first: ground or pot

This is the only decision that really matters with mint, and it has to be made before you plant, not after. Everything people write about mint being a thug follows from getting this one wrong.

1. When planting in the ground is fine A narrow strip enclosed on three sides by paving or walls, or a bed you are content to give over to mint for several years. If nothing else perennial is nearby and you can simply tread on what escapes, mint grows best in the ground.
2. When it has to be a pot A corner of a border, the end of a vegetable bed, anywhere touching a lawn. In all of those the runners will travel into the next area, and from the following year mint appears between your other plants.
3. If you are unsure Grow it in a pot for the first year. Once you know you like the variety and where you want it, you can always plant it out. Going the other way means digging runners out of a border.

Where the runners go, and when

The runners are white, jointed and about the thickness of a pencil, and they travel mostly in the top six inches (15 cm) of soil. They move fastest at two points in the year.

Keeping it in a pot

A pot solves the spreading problem completely, but only if you also stop the runners escaping through the drainage holes and over the rim.

1. Use a large, deep pot At least ten inches (24 cm) across and genuinely deep. In a shallow pot the roots fill it quickly and it dries out in summer, and you get small leaves with little scent. Ordinary compost is fine.
2. Do not stand the pot on soil A stem that flops over the rim and touches the ground roots at the node and starts a new plant. Raise the pot a few inches on bricks and use a saucer, and there is no route out.
3. Divide it once a year Once pot bound, the leaves shrink and the scent thins. In spring or autumn, tip it out, keep a third of the vigorous outer growth and replant that. Give the rest away.
4. Plenty of water, very little feed Mint dislikes drying out, so water thoroughly when the surface dries. Too much fertilizer gives you large leaves with weak scent, so a little slow release in spring and autumn is enough.

Runners will come out of the drainage holes and root into the ground below. Move the pot once a year and check underneath.

Planting in the ground with a barrier

A barrier is not permanent unless you check it. The annual walk around the edge is what makes the difference between contained and gradually escaping.

1. Sink a bottomless container Take a large pot or deep container, remove the base, and sink it with the rim standing an inch or two (3 cm) proud of the soil. Level with the soil and the runners simply go over the top.
2. Barrier board a foot deep Most runners stay in the top six inches, but sink a barrier at least a foot (30 cm) down for margin. They escape through joints, so overlap the sections.
3. Only cultivate inside the barrier Raking across the barrier drags fragments of runner outside, and each fragment becomes a plant. Keep the trowel inside and knock the soil off before you bring it out.
4. Walk the edge every spring Once a year, walk round the outside of the barrier, and where you find a shoot, follow the runner back and pull it. Once a year is enough to hold the area.

Getting it back once it has spread

Clearing mint is a two season job rather than a one afternoon job, and knowing that in advance stops it feeling like a failure.

1. Dig in autumn or early spring Choose a time when the top growth is small and the runners are easy to see. Digging through summer growth means fragments get lost in the soil and you miss them.
2. Work from the outside in Cut off the leading edge of the spread first and work back towards the center. The other way round pushes runners outward as you dig.
3. Pick out every white runner Sift the soil as you go. Runners snap easily between your fingers, so follow them rather than pulling hard, and lift them whole.
4. Check again the following spring You will not clear it in one go. Dig the shoots that appear the next spring and after two seasons it is largely gone. Even just pulling every shoot you see reduces it substantially.

Do not pile the runners you dig up in a corner of the garden. They root there. Shake the soil off and dry them out, or put them in the household waste.

Growing it near other plants

Mint is often recommended as a companion plant, and it does work, but only if you put it next to the bed rather than in it.

1. Not in a vegetable bed Runners cross the bed and come up between root crops. If you want mint nearby as a companion, stand the pot at the end of the bed and you get the same effect.
2. Be careful in a perennial border The top dies back in winter so you cannot see where the mint is. It all comes up at once in spring, and small perennials that were there the year before have gone.
3. Keep it away from dry loving herbs Rosemary and thyme want dry soil and mint wants moisture. In one container the watering cannot suit both.