Making the most of the sweet scent of summer

The delicious, tangy smell of tomato plant leaves is one of the season’s sensual delights

I’ve often wondered if we grow tomatoes as much for the scent of their leaves as for the taste of their fruit, because that sweet, tangy perfume is one of the glories of the vegetable garden, a wistfully evocative smell that sings of midsummer and sunny days working in the garden .

Once experienced, it's as curiously addictive as it is unforgettable. The cook and gardener Nigel Slater admits to liking it so much that he's formed the compulsive habit of regularly stroking the leaves of his own home-grown tomato plants. "Each time I pass them on my way up the garden, I rub their leaves and instantly sniff my fingers", he writes in his excellent new book, Tender, adding that he finds the perfume of the bruised leaves "faintly erotic".

The eccentric American perfumer, Christopher Brosius, is a fan too (cbihate perfume.com), so much so that he recreated the smell of tomato leaves as part of his collection of individual “accords” (the term that perfumers use to describe “a single scent that captures a very specific smell”). But Brosius is a man who appreciates the deep emotional connections between smell and memory, which is why one of the very first scents he ever made was called Dirt, and was a recreation of the smell of fresh, damp earth.

He’s since gone on to design many more perfumes, saying that, “I love the scents of green growing things: fresh cut hay, newly mown grass, the sharp bitter smell of weeds yanked from the garden”. Check out his website, if only to savour the descriptions of some of the other unusual scents available (these include Burnt Wood, Clean Sheets, Old Fur Coat, Wet Lawn, Cold Pressed Lemonade and Butter Crunch Lettuce).

In the OPW gardeners’ glasshouse in Phoenix Park, there’s no smell of freshly pulled weeds, old fur coat or freshly pressed lemonade but the scent of growing tomato plants is so strong that it meets you at the entrance, coming in perfumed wafts from the open doorway. Already 150cm-180cm tall, most of the plants are being grown in bags of garden compost (three plants per bag) with all unwanted side-shoots and basal shoots being nipped out when they develop.

“We neglected them while we were getting the walled garden ready for Bloom, so they needed a lot of pruning to get them back in shape,” admits Meeda, as she points to the wilting pile of unwanted shoots lying in a heap on the ground.

“They’d got themselves into a bit of a tangle and we had to cut away quite a few shoots but you need to do that if you want to get a good crop of fruit later on.”

Meeda and Brian are growing three different varieties of tomato, Sweet Olive (cherry), Octavio (standard) and Rosado (plum), in bags in the glasshouse, as well as a dwarf cherry variety called Tumbler that’s being grown in small, two-litre pots.

“They say that you can grow three Tumbler plants in a 30cm hanging basket so we reckon that there should be just about enough room in a two-litre pot for one plant as long as we keep it well-fed and well-watered,” explains Brian. Unlike the Tumbler tomatoes, the other varieties being grown by the OPW gardeners need some form of support and so Meeda is training them up taut lengths of garden twine, which are tied to a horizontal glasshouse support high above the heads of the plants.

“I tie one end of the string to the ridge of the glasshouse and the other end loosely to the base of the plant stem. Then I gently wind the main stem around the string until it’s got enough support to not flop over,” explains Meeda. “Without it, the stems would bend and crack as the fruit begins to swell and get heavy”.

The OPW gardeners planted the tomatoes about five weeks ago and will begin liquid feeding them within the next few days as the flowers begin to “set” fruit.

“The nutrients in the compost were using last for about six weeks or so, after which we need to keep feeding the plants regularly with a high-potash liquid feed. Otherwise growth would slow right down and they’d end up showing signs of nutrient-deficiency like yellowing of the leaves or blotchy ripening of the fruit. It’s also really important to keep the plants watered and ‘damped down’ but to avoid overwatering or wetting the leaves too much as that’ll encourage diseases like blight and leaf mould as well as reducing the flavour. You need to get the balance right, and have the compost moist but not wet”, says Brian.

Suitable liquid tomato feeds are available from most garden centres while organic-minded gardeners will prefer to use either a seaweed-based fertiliser (Health-Sea Liquid Seaweed is available from fruithillfarm.com) or to make their own from comfrey leaves.

If so, a booklet called Comfrey for Gardeners, which explains the different ways in which comfrey is useful in the garden, can be ordered from the Garden Organic website (organiccatalogue.com).

The OPW gardeners’ tomato plants are being allowed to grow to at least two metres tall, after which time Brian and Meeda will “stop” the plants by nipping out the tip of the growing shoot a couple of leaves above the last flower truss, to encourage the ripening of any fruit.

Emerging flower trusses, by the way, can sometimes be confusingly similar to young side shoots, so take care when you’re pruning your plants.

Elsewhere in the glasshouse, the OPW gardeners are growing fat pots of basil and boxes of lemongrass as well as the toothache plant, Acmella oleracea(also known as Spilanthes oleracea). Supposedly the leaves of this Brazilian native are tasty in salads but the flowers are a different matter entirely. Experimental chefs may enthuse about the taste of its yellow-red flowerbuds (they're nicknamed Buzz Buttons) but Brian has been forced to admit that they're revolting, (Meeda, quite wisely, refused point-blank to even taste them).

In the spirit of curiosity (call it nosiness), I ate one flower, which tasted mouth-wateringly awful – sour, salty and bitter all rolled into one. In fact, I’m not surprised that the active ingredient in the plant, Spilanthol, has proven highly effective at killing mosquitos and to have a strong diuretic action in rats. No, not surprised at all.

So goodbye to the toothache plant. Unlike the deliciously memorable smell of tomato leaves, the taste of its flowers is an experience that it’s definitely best to forget, and the sooner the better.

• The OPW's Victorian walled kitchen garden is in the grounds of the Phoenix Park Visitor Centre, beside the Phoenix Park Café and Ashtown Castle. The gardens are open daily from 10am to 4.30pm.

• Next week the Urban Farmer will cover growing strawberries.

• Fionnuala Fallon is a garden designer and writer.