How to grow mint in containers without it taking over

Why does mint spread so aggressively?

Mint isn't a polite clumping herb like chives. It runs. Underground rhizomes push out 15 to 30cm in every direction each season, and every node throws up a new shoot. Plant a small pot of mint in a vegetable bed in April and by August it will have invaded the rows either side and started eyeing up the lawn.

The only thing that actually works is a physical barrier. A 25cm container is the simplest version. A buried bucket with the bottom cut out does the job too, sunk into a bed to make a kind of pseudo-island.

Picking the right variety

A pot of mint should be a pot of one variety. Mints cross-pollinate freely, and the seedlings, and even some rhizomes, drift towards a generic peppermint flavour after a few years. Keep varieties physically apart (different pots, ideally 2m apart) if you want to preserve their character.

The four worth growing:

• Moroccan mint. Clean spearmint, no menthol; the tea mint.
• Common spearmint. The workhorse; salads, lamb sauce, drinks.
• Peppermint. Strong menthol; desserts, ice cream, infusions.
• Apple mint. Soft, fruity, a touch hairy; jelly and salads.

Skip pineapple mint (looks pretty, tastes thin), Bowles' mint (huge but coarse), and chocolate mint (a novelty that disappoints in the teapot).

Setting up the container

1. 1

   Pick the pot

   25cm diameter, 25cm deep. Terracotta breathes well; plastic works too, but dries less predictably.

2. 2

   Drainage layer

   Despite mint's love of moisture, the pot still needs drainage holes and a 2cm crock layer at the bottom. Stagnant water rots the rhizomes.

3. 3

   Use rich compost

   Peat-free multipurpose compost, with a handful of slow-release fertiliser mixed in. Mint is hungry. Lean soil gives you weak flavour.

4. 4

   Plant one variety

   A 9cm garden-centre pot of mint is plenty. Fill the rest with compost and water deeply once.

5. 5

   Position

   Half-sun to full sun. South-facing is fine as long as you keep on top of watering; east or west-facing is easier through mid-summer.

Watering and feeding

Mint drinks. In a sunny pot in July, expect to water daily; in cooler weather, every 2 to 3 days. The leaves wilt dramatically when thirsty, but the plant bounces back within an hour of a deep water, so wilting isn't a crisis, just a nudge that you're behind on watering.

Feed once a month from May to August with a balanced liquid feed at half strength. Skip feeding in autumn. You want the plant to slow down, not push on.

The annual divide

In its first year, a mint pot is glorious. By midsummer of year two it starts looking stringy. Long bare stems, smaller leaves, weaker flavour. That's the rhizomes strangling each other in a root volume they've completely filled.

Every March, tip the pot out, slice the rootball into three or four wedges with a serrated knife, repot one wedge in fresh compost, and give the rest away (or compost them. They won't regrow from a heap that's running hot). A divided mint is a fresh mint, and skipping this one job is why most kitchen-garden mint disappoints by year three.