Why Mint Refuses to Stay Put

Mint is one of the most rewarding herbs a UK garden can offer. It'll grow in shade, shrug off a wet winter, and give you handfuls of leaves from April right through to the first frosts. The trouble is that it does all of this a little too enthusiastically. Unlike clump-forming herbs such as oregano or thyme, mint spreads by runners — creeping stems that travel just below the soil surface and pop up new plants wherever they fancy.

Left to its own devices in a border, a single supermarket pot can colonise a square metre within two seasons, threading itself through neighbouring perennials and making itself almost impossible to remove without disturbing everything else. The answer isn't to give up on mint. It's to give it walls.

Choosing the Right Container and Compost

Mint has a vigorous root system, so a dainty pot won't hold it for long. Choose something at least 30cm across and 30cm deep, with generous drainage holes. Terracotta, glazed ceramic, or a sturdy plastic pot all work well; the weight of terracotta is a bonus on a windy patio. Avoid anything narrower than a standard bucket, or you'll be repotting by July.

For compost, a soil-based mix such as John Innes No. 2 is ideal. It holds moisture without turning to sludge, and it has enough weight to keep the pot steady. A peat-free multipurpose compost works too, but mix in some garden soil or coarse grit to stop it drying out so rapidly in summer. Mint likes rich, damp conditions, so add a handful of well-rotted manure or garden compost at planting time if you have it.

Crucially, never mix shop-bought compost with soil from the border where mint has already grown — you may be importing fragments of root that will happily regrow.

Sinking a Pot into the Border

If you want mint in a flowerbed or among your cottage-style planting, the neatest trick is to bury the pot so its rim sits 2–3cm proud of the soil. This hides the plastic or terracotta, keeps the plant looking as though it belongs, and still stops the runners in their tracks.

• Dig a hole slightly wider and deeper than the pot.
• Check the rim will sit above soil level — if it's flush or below, runners will simply hop over the edge.
• Sit the pot in, backfill around it, and firm gently.
• Water well, then mulch around the rim with bark or gravel to tidy the join.

If you'd rather not see the rim at all, leave a shallow lip and disguise it with a ring of low-growing plants such as alpine strawberries or creeping thyme — but remember to check it each spring.

Growing Mint in Patio Pots

Free-standing containers are simpler still, and they let you move the plant into the shade when a heatwave hits. Position pots where they get morning sun and afternoon shade, or dappled light all day. Full sun is fine in the north, but in southern counties it will bolt, flower early, and the leaves will turn coarse and bitter.

Watering matters more than feeding. Container mint dries out fast, so check daily in July and August, and water until it runs from the drainage holes. Feed with a diluted liquid general-purpose fertiliser every three to four weeks through the growing season — no more, or you'll get all leaf and no flavour. Pinch out the growing tips regularly to keep plants bushy, and cut out flower spikes as soon as they appear if you want tender leaves for longer.

Varieties Worth the Space

Different mints earn their keep in different ways, so it's worth growing two or three in separate pots.

• Moroccan mint — the classic for tea, with a clean, sweet flavour.
• Spearmint — the traditional mint sauce variety, hardy and reliable.
• Apple mint — softer and slightly fruity; lovely with peas and new potatoes.
• Pineapple mint — variegated leaves that brighten a shady corner.
• Basil mint — a peppery, unusual choice for salads.

Keep varieties apart if you can. They cross freely, and a mixed pot soon loses its distinct character.

Refreshing Tired Plants Every Few Seasons

Even in a pot, mint eventually exhausts its compost and becomes woody in the centre, with all its energy pushed to the edges. Expect to refresh plants every two to three years. Spring is the best time, though early autumn works if you're in a mild area.

Tip the plant out, then pull or cut away the woody middle and tease out the healthiest young shoots from the outside of the rootball. Replant three or four of these in fresh compost, water them in, and compost the rest. You can also take 10cm cuttings in summer — strip the lower leaves, stand them in a jar of water on a windowsill, and pot them up once roots appear.

Watch for mint rust, which shows as bright orange spots on the undersides of leaves, and for ragged holes made by mint beetle. A hard cut back, removing all affected foliage and binning it rather than composting it, usually solves both. With a little containment and a biennial overhaul, a single pot of mint will keep you in tea, tabbouleh and mint sauce for years.