A sharp citrus tang is essential in the kitchen, and in the cocktail cabinet – not as a substitute for lemon but to provide that extra edge to drinks, salads, and hot and chilled soups, as well as savoury dishes and desserts… not to mention Asian cuisine. And there’s a number of citrus-flavoured plants that can be relied on to bring us the flavour and which are also easy to grow.
Lemon balm (Melissa officinalis) should probably top your list as this tough perennial packs a real lemony punch and is also exceptionally easy to grow in sun or shade. In fact it can be a little too easy as it self seeds enthusiastically. Keep nipping out the shoot tips to use and that will prevent it flowering and seeding. It can spread strongly, but the yellow variegated form, ‘Aurea’, and the all-yellow form ‘Allgold’, grow a little less vigorously (although they may scorch in hot, dry positions); ‘Allgold’ self seeds true; ‘Aurea’, not so much.
There’s a number of mint varieties whose foliage has citrus flavours and these, of course, are also vigorous. ‘Lemon’, ‘Lime’ and ‘Orange’ are all descriptively named forms of peppermint, Mentha × piperita. The pale green foliage of ‘Lemon’ and the rich dark ‘Lime’ have a more true flavour than the almost purplish leaves of ‘Orange’. Perversely, M. × piperita f. citrata has a lavender/bergamot scent! The usual mint warnings apply - they're best planted in containers or restricted in some way to prevent them spreading too much.
The names of the lemon-scented thymes have become very confused and, although the name Thymus × citriodorus is used for a number of different forms at least they all should be lemon-scented. ‘Culinary Lemon’ will give you the best flavour, and there are several variegated forms but, again, the names are muddled. Look for ‘Archer’s Gold’, ‘Aureus’ (see photo) and ‘Bertram Anderson’. All are bushy, rather than creeping, and all enjoy sun and well-drained soil.
Lemon grass (Cymbopogon citratus) has become widely used in recent years, especially in Thai recipes and drinks. It makes an attractive, upright container specimen in summer, or with coleus (Solenostemon) or Plectranthus in a large container. But this is not a hardy plant and needs a minimum temperature of 7°C (45°F), so move it into the conservatory for winter.
Finally, a shrub. Lemon verbena (Aloysia citrodora), makes rather a thin plant that can reach 3m (10ft) in well-drained soil on a sunny wall when left unpruned. But snipping off shoots for summer drinks helps keep it shorter and bushy, and the leaves are always so tempting that keeping it in shape is not difficult.
Look out, too, for lemon basil (Ocimum × africanum), the many new forms of the giant Mexican hyssop (Agastache mexicana), and even lemon catmint (Nepeta cataria spp. citriodora 'Lemony'). All are well worth a try and all have that sharp lemon tang.