Makes perfect scents: Let the perfumed tropical nurseries at Kew soothe you

Dendrochilum - with delicate interlocking white flowers like the elegant bony backbone of a fossil fish - hardly resembles our normal notions of an orchid (Royal Botanical Gardens, Kew)

It's easy to be sad in February. It's easy to find your brain filled with worries, with fragments of tasks you should be getting on with, a perpetual to-do list cycling in the frontal lobes.

You could step out into the cold, late-winter air, and take a long walk around streets still scattered with the windblown trash from recycling day; you could swim 100 lengths, feeling it all wash away with each sleek turn. Or, distinctly more pleasantly, you could let perfume fill your brain.

Scent does something physical to me. I always used to think that perfume was just for wearing to parties, essentially a posher kind of teenage preventative against the dreaded and endlessly discussed BO. These days, I wish I could see a brain scan of what's happening inside my head when I pull back the door of the Tropical Nurseries at the Royal Botanic Gardens, Kew, on a fierce day of spitting rain, and step inside.

I'd like to think that the scan would show a tiny pulse of deep rose, beginning at the core of my olfactory bulb, which spreads within milliseconds to my amygdala, the frontal cortex, the hippocampus: staining my whole brain sunset-pink within a fraction of a moment.

I'd like to think this because that's how it feels: you breathe in the scent inside this greenhouse, and your whole head fills with it. The daily niggles are swept away by a wave of perfume that seems as if it goes straight through your nose to your brain, completely, instantly, giving you a headrush, displacing whatever rubbish it was that you were churning over previously.

The Tropical Nurseries are normally off-limits to the public, as they are the workplace of Kew's specialist cultivators, growing on tiny micropropagated conservation rarities as well as huge plants reaching to the roof. However, during the current Orchid Festival, which runs to 9 March, guides are taking special tours around these prestigious specialist glasshouses, letting you add another whole level of treat to the festival glasshouses and the riotous public displays.

The first scent in the Tropical Nurseries is a row of citrus trees, heavy with fragrant blossom. We look like a line of dogs turning our noses towards it. But room after room is filled with plants, in neat, green rows, and each has a scent of its own, to fill your lungs, your nose, your entire head.

Here you can see the growing mediums, find out about Kew's specialist cultivation techniques, and best of all, sniff. Here is Dendrochilum (pictured), with delicate interlocking white flowers like the elegant bony backbone of a fossil fish, hardly resembling our normal notions of an orchid. But what perfume! "In the morning, I think it starts off like vanilla, and in the afternoon, it goes a little bit more like one of those spicy gobstoppers," one of the horticulturalists tell me.

Reading about the smell centre of the brain on that well-known totally true source of knowledge, Wikipedia, I'm delighted to discover a section claiming that rats which have their olfactory senses removed are used to research antidepressants, so close is the effect to that of human depression. Forget about the wasted hour-and-a-half in that meeting where you might as well have been having your nails done; forget about the Friday afternoon reply you were waiting for which never arrived. Clear your mind. Breathe in perfume.

Tours of the Tropical Nurseries (on Saturdays) and Orchid Nursery (Thursdays) take place throughout the Orchid Festival and must be booked at kew.org in advance, priced £5 (or £15 including a Q&A with staff cultivators)

What to do: Highlights of the Orchid Festival

Orchid Hunters' Island

To be found in the centre of the Princess of Wales conservatory. Complete with 19th-century mahogany collecting boxes used on Kew expeditions.

Micropropagation jars

To be found in the cool orchid display. Showing the microscopic scale of Kew's modern orchid-growing, used when conservation is a major issue.

Tillandsia harrisii

A spectacular individual plant with a dramatic story, confiscated by the UK Border Agency after being illegally imported. Seems to be loving its current home…

Vanda Cascade

Vandas in every shade of violet and mauve, hanging down towards the visitor, providing the perfect photo opportunity.