As someone both blessed and cursed with a keen sense of smell, I sometimes wonder what it would be like to lose it. To never again inhale, for example, the sweetness of a rose. To be forced to go without the spicy, spring perfume of witch-hazel, or the fresh-earth scent of newly dug potatoes, or the sharp, vegetal tang of tomato plants softly baking in a hot glasshouse in high summer.
Indeed it’s the aromatic foliage of some species of plants – which are every bit as scent-loaded as but far longer-lasting than their floral counterparts – that I think I’d miss most.
Put aside, for example, the fact that the scent of mint is proven to boost our ability to concentrate, as well as to bolster memory function, ease a headache and soothe a sore throat. Instead, imagine not being able to enjoy the sensory pleasure that comes from sucking its clean fresh perfume deep into your nose and lungs. Likewise, imagine a world without the almost camphorous whiff of rosemary. Or the woody scent of sage. Or the herbal, slightly floral tang of bay, marjoram or thyme.
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Proving the old adage that not all books should be judged by their cover, it’s intriguing that some of the most ordinary-looking species of plants have the most intensely perfumed foliage. Crush just one tiny leaf of the innocuous-looking lemon verbena (Aloysia citriodora) between your fingers, for example, and you’ll be instantly transported back to your childhood and the sugary, citrusy, sticky pleasure of a bag of lemon bonbons.
Many of the scented-leaf pelargoniums share that same magic power, their oh-so-ordinary appearance belying the fact that, depending on the particular variety, their foliage can smell of pine trees (Pelargonium fragrans), cola bottles (P ‘Torrento’); rosewater (Pelargonium ‘Attar of Roses’); lemons (Pelargonium ‘Lemon Fizz’); and oranges (Pelargonium ‘Prince of Orange’). For this reason, many of them can be used in cooking to flavour cakes, puddings, pies, jellies, ice cream, biscuits and vinegars, as well as herbal teas and lemonade.
For many people the foliage of blackcurrants and flowering currant carries a distinct whiff of cat urine
Mint is similar in its beguiling range of fruity flavours, which include pineapple mint (Mentha suaveolens ‘Variegata’; apple mint (Menta suaveolens); banana mint (Mentha arvensis ‘Banana’); strawberry mint (Mentha spicata subsp citrata ‘Strawberry’) and grapefruit mint (Mentha x piperata f citrata ‘Grapefruit’). For chocoholics, there’s even a chocolate mint (Mentha x piperata f citrata ‘Chocolate’).
The foliage of many popular varieties of shrubby ornamental salvias such as Salvia ‘Hot Lips’, Salvia ‘Love and Wishes’ and Salvia yangi (Russian sage, formerly known as Perovskia atriplicifolia) also releases a pleasantly sweet, slightly minty scent on hot days, or when bruised. So do the leaves of the decorative, summer-flowering perennial known as bergamot or scarlet bee-balm, (Monarda didyma), whose leaves and young shoots can be eaten raw or cooked, added to salads and drinks, or used to make a herbal tea.
Another garden plant famed for its aromatic foliage is myrtle (Myrtus communis), the shrub or small tree whose aromatic, edible leaves are used as a flavouring in cooking. Fascinatingly, eating its leaves also causes people’s urine to smell of violets, an intriguing example of the complex ways in which plants affect our sensory experience of the world.
Other plants with strongly scented foliage that can be commonly found growing in Irish gardens include the sweet gum (Eucalyptus). This tree’s waxy, evergreen leaves contain the minty-smelling chemical known as eucalyptol and other terpenes (volatile organic compounds produced by many plants) called cineol, pinene and limonene that combine to create its distinctive perfume. Another is Cercidiphyllum japonicum, commonly known as the katsura tree, whose autumn foliage smells of toffee apples. And of course there are the conifers, a group of plants known for their strongly aromatic foliage from the citrusy smells of Douglas fir (Pseudotsuga menziesii), Monterey cypress (Cupressus macrocarpa) and juniper (Juniperus scopulorum) to the resinous smell of pine trees.
Certain species of escallonia also pack a powerful whiff of curry that’s strong enough to make some feel queasy
On the other side of the fence are the garden plants that are somewhat unpleasant smelling. Box hedging (Buxus sempervirens), for example, was famously banished by England’s Queen Anne from the royal gardens of Hampton Court on account of the distinctively acrid scent released by the plant on very hot, sunny days, or when clipped or bruised. For some, but not all of us, that smell, which is caused by oils and terpenes contained within the plant, is strongly reminiscent of cat pee. Likewise, for many people the foliage of blackcurrants and flowering currant carries a distinct whiff of cat urine, as do the leaves of the shrub known as Mexican orange blossom (Choisya ternata).
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Similarly, if you’re not a fan of curry, then don’t grow the pretty, silver-leaved Helichrysum italicum, whose sulphurous scent earned it its common name, the curry plant. Certain species of the evergreen hedging shrub known as escallonia also pack a powerful whiff of curry that’s strong enough to make some feel queasy, including Escallonia myrtoides, Escallonia viscosa, E coquimbensis and E illinita. Other useful garden shrubs and perennials such as cotton lavender (Santolina chamaecyparissus), tansy (Tanacetum vulgare), and artemisia are also known for the strong, slightly bitter smell of their leaves, although rarely to the point where gardeners deliberately avoid growing them.
Luckily, we don’t have snakes in Ireland... But if we did then it would be yet another reason to grow lavender
Fascinatingly, most plants with strongly perfumed or aromatic leaves have a significant advantage when it comes to fighting off attacks from pests such as slugs, snails, deer, rabbits, and insects, which typically dislike their taste and smell.
Tansy, for example, is a natural insect repellent that was traditionally used to treat lice, fleas and scabies, while many organic gardeners still use an infusion of garlic to ward off slugs and snails. For the same reason, kitchen gardeners also often use members of the onion family to protect plants from attack by growing them tactically next to more vulnerable crops such as brassicas and leafy vegetables, a technique known as companion planting.
Likewise, mint is so strong-smelling that it was traditionally used as what’s known as a “strewing herb” to freshen homes and deter pests, as well as by farmers in granaries to deter mice and rats, which loathe its clean, fresh scent.
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Luckily, we don’t have snakes in Ireland (thank you St Patrick). But if we did then it would be yet another reason to grow lavender, a plant long famed around the world for its intensely perfumed foliage. Not only does it have a long history of use in regards to its powerful antiseptic properties, as well as in cosmetics, soaps and perfumes, and to flavour cakes and icecrems, lavender can also be used topically to treat snake bites – yet more proof of how so many of our favourite scented garden plants are far more than just a pretty smell.
This week in the garden
Avoid the mistake of leaving recently harvested vegetable beds empty, which leaves them vulnerable to weed infestation and leaching of nutrients from the soil. Instead cover the ground with an organic mulch such as home-made garden compost, fresh clippings from a tightly mown lawn or well rotted manure, or sow a green manure as a “catch crop” to suppress weed growth, replace lost nutrients and protect the soil. Green manures suitable for sowing at this time of year include phacelia, mustard, clover, grazing rye, buckwheat and winter tares.
Once the plants have finished flowering, lightly clip back lavender, santolina and rosemary to encourage healthy, bushy plants and prevent them from becoming straggly. The traditional advice with lavender was to always avoid cutting into the old wood, but this has changed in recent years, with the recommendation now being to cut plants back to approximately 25 inches, while always making sure to cut back to just above a pair of new shoots.
Dates for your diary
Saturday, August 5th The last day of this year’s Carlow Garden Festival, which finishes with a bang via a talk about the famous gardens of Great Dixter in the UK by its head gardener Fergus Garrett at Huntington Castle (3pm-4.30pm). Pre-booking is essential. carlowgardentrail.com
Sunday, August 6th (10am-5pm, free admission): the Annual Farmleigh Autumn Plant Fair returns to the Farmleigh Estate in the Phoenix Park (admission free) with stands by many of the country’s very best small specialist nurseries and lectures by Mary Keenan, editor of the Irish Garden and co-owner of Gash Gardens in Co Laois, and flower-arranging demonstrations by Chelsea gold-medallist Christopher White of Three Gates Nursery.
Saturday, August 26th (3pm-5pm): the Delgany & District Horticultural Society will be hosting its annual Dahlia Show at St Patrick’s Primary School, Church Road, Greystones, Co Wicklow. Potential exhibitors should please email their entry forms to the show secretary at ddhs.showentries@gmail.com on or before Thursday, August 24th.
