Two herbs that earn their keep

By midsummer, most UK gardens have far more mint than they can reasonably use. It runs along the edge of a border, pops up in the lawn and fills the gaps between paving slabs, and every year it seems to arrive a fortnight earlier. Lemon balm behaves much the same, though it is quieter about it. Between them, these two herbs will keep a household in fresh tea from April until the first proper frost, and they cost nothing but a few minutes of picking.

Spearmint, Moroccan mint and apple mint all work well in a cup, and lemon balm — Melissa officinalis — brings a soft citrus note that blends beautifully with them. Our damp, mild climate suits both herbs down to the ground. Neither is fussy, neither needs feeding, and both will grow happily in a pot on a north-facing windowsill if that is all the space you have.

Picking at the right moment

The essential oils that give these herbs their scent are at their most concentrated in mid-morning, after the dew has dried but before the sun gets fierce. Pick then if you can. Take the top two or three pairs of leaves and pinch the stem just above a leaf node, which encourages the plant to bush out rather than run to flower.

For lemon balm, harvest before the flowers open. Once those small white blooms appear, the citrus scent fades noticeably and the leaves taste distinctly of nothing much. Mint is more forgiving, but young growth is always the sweetest.

• Water the plants the day before you plan to pick, never the morning of — wet foliage bruises and the leaves keep better dry.
• Never strip a stem bare; leave at least two sets of leaves behind so the plant can regrow.
• Carry a shallow basket or a paper bag rather than a plastic tub, which sweats and wilts the leaves.
• Aim for about ten mint leaves or eight lemon balm leaves per mug. Lemon balm is considerably stronger, so start cautiously.

Preparing and steeping

Rinse the leaves well in cold water. This matters more than it sounds: mint grows close to the ground, and a colander of picked leaves almost always hides grit, a stray greenfly and the occasional slug. A gentle swill under the tap is enough — do not scrub or bruise the leaves yet.

When you are ready to brew, tear or lightly crush the leaves between your fingers and drop them into a mug or a small teapot. Bruising is what releases the oils, so do it just before the water goes on rather than in advance.

Use just-boiled water — not a furious rolling boil, which can flatten the delicate citrus notes in lemon balm. Something around ninety degrees is ideal, which simply means letting the kettle settle for thirty seconds after it clicks off. Cover the mug with a saucer while it steeps. The oils are volatile, and covering keeps them in the cup rather than in the kitchen. Five to seven minutes is about right. Strain, or fish the leaves out with a spoon, then sweeten with a little honey if you like. Do not leave mint steeping for half an hour; it turns bitter and slightly medicinal.

Blends worth trying

Once you have the basic method, the garden offers plenty of variations. A few favourites:

• Equal parts mint and lemon balm, which is soothing in the evening and tastes like a summer evening smells.
• Lemon balm with a slice of fresh lemon and a sprig of thyme for something sharper and more refreshing.
• Mint with a bruised cardamom pod or a few slices of root ginger, steeped a minute or two longer.
• For a cold version, brew at double strength, cool completely, then pour over ice with a few cucumber slices and a sprig of mint.

Keeping a reliable supply

Mint is a thug. Plant it in a large pot sunk into the border, rim just above soil level, or give it a rough corner where nothing else is expected to survive. Lemon balm self-seeds freely, which in a relaxed cottage-style planting is a gift rather than a nuisance — let it wander among the hardy geraniums and aquilegias, and simply cut the flower spikes back before seed sets if you want to keep it in check.

Both herbs do well in partial shade, which makes them useful plants for awkward spots. A damp shade bed works particularly well: a clump of apple mint beside male fern and soft shield fern, where the ferns enjoy the same moisture and the mint fills the gaps while the fronds unfurl. Ferns ask for little beyond consistent damp and their crowns kept clear of mulch, so the two sit together comfortably. In dry spells, water both — thirsty mint and lemon balm will sulk and flop, and the leaf flavour suffers.

Drying and freezing for winter

To keep the harvest going, cut whole stems on a dry morning and either hang them in small bunches in a dark, airy room or drop them into a paper bag with the stems poking out of the top. Once the leaves crumble easily, strip them and store in an airtight jar away from light. Dried mint keeps its character well for a year or so; dried lemon balm fades quickly. Freezing suits it far better — pack whole leaves into ice cube trays, top up with water, and drop a cube straight into a mug when the garden has gone quiet.