Watercress

Sweet basil is the essential companion to tomatoes — both in the garden and in the kitchen. In UK conditions, it's best treated as a tender annual, started indoors from April and planted out only after all frost risk has passed in late May or June. It performs brilliantly on a sunny windowsill or in a greenhouse, but struggles outdoors in cool, wet summers. Pinch out growing tips regularly to encourage bushy growth and prevent it from flowering too quickly. Once basil flowers, the leaves lose their intensity. Harvest by cutting whole stems rather than picking individual leaves — this promotes fresh growth. 'Genovese' is the classic large-leaf Italian variety; 'Greek' basil forms a compact ball of tiny leaves that's more tolerant of cooler weather.

English lavender is one of the most reliable and rewarding perennials for UK gardens. Its silvery foliage and purple flower spikes are irresistible to bees and butterflies, making it a pollinator magnet from June to August. It thrives in poor, well-drained soil — in fact, rich soil and heavy clay are its enemies, causing leggy growth and winter die-off. Plant it in the sunniest, most well-drained spot you have. The key to keeping lavender compact and productive is annual pruning: cut back hard after flowering, removing spent flower stems and about a third of the leafy growth, but never cut into bare wood. 'Hidcote' and 'Munstead' are the most popular UK varieties. Lavender hedging along allotment paths is both beautiful and functional — the scent helps deter deer and rabbits.

Mint is one of the most vigorous herbs you can grow — which is both its greatest strength and its biggest challenge. Left unchecked in open ground, it will colonise entire beds via underground runners. The solution is simple: always grow mint in containers, or sink a large pot into the soil to contain its roots. Beyond this one caveat, mint is virtually indestructible. It thrives in partial shade and damp conditions that would stress most herbs. Harvest regularly by cutting whole stems, which encourages fresh bushy growth. There are dozens of varieties worth growing: spearmint for new potatoes and peas, peppermint for tea, apple mint for a milder flavour, and chocolate mint for a genuinely chocolatey undertone. Replace plants every 3–4 years when they become woody and less flavourful — simply dig up a section of runner and replant.

Rosemary is a Mediterranean evergreen that has adapted brilliantly to UK gardens, shrugging off cold winters as long as it has good drainage. It's one of the most useful culinary herbs — essential for roast lamb, focaccia, roast potatoes, and infused oils. The plants develop into handsome woody shrubs over time, with some varieties reaching over a metre tall. 'Miss Jessopp's Upright' is the best variety for hedging; 'Prostratus' cascades over walls and raised bed edges. Rosemary flowers early in the year, providing vital nectar for bees emerging from hibernation in February and March. It's almost impossible to kill from neglect — overwatering and waterlogged soil are the main killers. Prune annually after flowering to prevent the plant becoming leggy and woody. Take softwood cuttings in summer for new plants — they root easily in gritty compost.