The essential oils in the foliage and peel of citrus fruits is known to have an uplifting effect: just add a slice of lemon to a glass of water and it seems to become doubly refreshing.
This citrus aroma is in the essential oil in lemon peel – a compound called limonene and this is that we mean when we talk about lemon-scented plants. This lemony smell that so many herbs have is from another compound, citral, which is present in the oils of several plants and this can be in the form of geranial which has a strong lemon scent or neral which is less intense but sweeter. The quantity of each will determine the intensity of lemon scent in the foliage and flowers of the lemon-scented herb.
Lemon-scented herbs to try in the garden
Lemon grass (Cymbopogon citratus), a zesty staple in Asian cuisine, is now a commonplace ingredient in our kitchens. In the UK, though, it is not hardy, so while many seed companies are offering seed and you can also coax supermarket-bought rolls of lemon grass into growth, it will need winter protection. I have brought lemon grass plants on from year to year in the heated greenhouse.
Lemon verbena (Aloysia triphylla) is a woody shrub that loses its foliage in winter, at which time it is not massively ornamental in the garden. Still it wins its place as a lemony herb, as in summer its foliage is wonderfully refreshing when you crush it in your hands and it is also very useful in the kitchen. It is not hardy below 4 degrees C, but I grow several lemon verbenas in containers, which I used to haul in and out of the greenhouse for the winter. Now, I let the lemon verbena plants take their chance outdoors. They are in the lee of the house, so in a protected spot.
In summer it blooms with small mauve flowers arranged in delicate upright spikes. The plants do do well in full sun and will grow to a height of about 4ft. You can pick the foliage for use all through the summer, but the aroma is best just before flowering. I nip out the flower buds to prolong the good leaf aroma, but eventually let it flower. The leaves can be used fresh to flavour oil and vinegar, in baking and in salads, as well as to flavour fruity desserts. Dried leaves are good for tea, in scented bags and pillows, and in potpourri.
Lemon balm (Melissa officinalis) can be too much of a good thing, as it self-seeds and spreads to form large clumps, but I think it is a great ground-cover plant in a sunny site. And of course, it and the golden leaf form ‘Aurea’ have wonderful lemony flavoured foliage. I cut it back after flowering in an attempt to curb self-seeding. It is a perennial herb and the golden form does well in shade, as full sun seems to bleach out its foliage.
The leaves make a refreshing tea and can be used to flavour casseroles, soups and salads. They are a good substitute for lemon grass. In addition you can use the leaves under running hot water to fragrance baths, and also dried, in herb pillows.
Lemon thyme (Thymus citriodorus) and variegated lemon thyme (T. x citriodorus ‘Silver Queen’) are attractive growing in containers or in the ground. They also look good growing in a gravelled patio area. The leaves of both are good with poultry, fish and in sauces and dressings. Like all thyme plants they are evergreen and perennial. They grow to form small woody shrubs and I always cut the plants back after they have flowered. Their flowers are bee-magnets, and you can also use the flowers in salads or in baking.
Mints have a range of aromatic foliage, some described as orange or grapefruit scented, but the one with the lemon scent is Mentha x piperita f. citrata ‘Lemon’. Like all mints it has a spreading growth habit and produces spikes of mauve flowers in summer. Grow it in a container to keep it from overtaking other plants. Harvest the foliage up until it flowers, then after flowering cut back and use the new foliage growth.
If I had to choose one lemon-scented herb for my desert island herb garden then it would have to be lemon basil (Ocimum basilicum x citriodorum). This small leaved, bushy basil, with white flowers, packs a powerful punch and revives my spirits, as I harvest it in the greenhouse. It transforms salads into culinary masterpieces. I sow basil in spring into trays in a heated propagator in the greenhouse. When they are large enough to handle I prick them out and pot them, two-three to a pot. I know that you can plant them out into the garden or grow them in containers on a patio during summer, but I prefer to keep them in the greenhouse, where I harvest regularly for daily use and to freeze, for future use.