Ah, the Clary Sage, I presume: On the hunt for the rarest plants

You don't need to be a snob to take a delight in plants no one else has ever heard of. Emma Townshend heads to the spring fairs to search out the weirdly wonderful

I don't really want to think of myself as a plant snob. I mean, plant snobs are people who talk in loud voices at flower shows so that you hear them being terribly knowledgeable. "It's Salvia sclarea turkestanica," they boom, "Very rare. That label is completely incorrect."

But there is a certain pleasure in seeing a plant for the first time. The pleasure of a plant-hunting discovery, when you realise the world just got a little bit bigger. It could be that salvia from a former Soviet republic, or the moment you realise that your own self-seeded poppies are producing blooms in a range of gaudy pinks Thompson & Morgan would pay to get their hands on. Either way, it's a proper buzz.

For this reason alone, garden-centre plant-hunting can be a dispiriting business. Garden centres are fab at this time of year for brightly coloured window-box fillers, baby vegetable plants and massed, bargain plants they've chosen to sell in high volume. But for unusual plants, those thrilling discoveries for which you feel not a single fragment of recognition, you need to go elsewhere.

Luckily, each year more and more organisations cotton on to the number of potential British plant-hunters hidden in our midst. These days, schools, charities and stately homes all run rare-plant fairs. You might think a rare-plant fair sounds like a guaranteed boring day out; yet they are a properly British experience you need to have at least once in your life. Sure, there will be a few plant snobs in tow. But you'll also overhear tantalising snatches of conversation about the best clematis for a shady patch, and get to try weird and wonderful local delicacies (watercress roulade and cheese scones, at my favourite Hampshire fair). Handsome young men carry your purchases to your car in wheelbarrows, for tips – and that's another thing you don't get at the garden centre.

And best of all, there will be carloads of plants, all looking their spruced-up best, on trestle tables and upturned crates, arranged to empty your pockets. I have more than once found myself driving back to the nearest cashpoint from one of these fairs, after realising that the 30 quid I turned up with isn't going to cover it.

Look out for gauras, the soft, pretty perennials with long stems of star-like flowers, a new favourite for those who want something a bit penstemon-ish to fill a gap. And all the different sea hollies in the Eryngium family, azure blue and totally stunning. Or just seek out Salvia sclarea turkestanica. The White Clary Sage, as it is known to acolytes, is an irresistible, foxglove-like spire of pinky-white flowers. Ooh, plant snobbery beckons.

Three local plant fairs

St Michael's School in London's Highgate, will run a spring plant fair on 8 May, from 10am-5pm. Fifteen specialist nurseries will be in attendance. Admission £2.50

Tremenheere Sculpture Gardens will be running the inaugural West Cornwall Plant Fair on 2 May from 10-5pm. An exciting range of Cornish nurseries will have plants on sale to match the extraordinary setting. Admission £5, under-11s go free; tremenheere.co.uk

Gilbert White's House in Selbourne holds my favourite annual plant fair (below). You will never encounter a better organised field-based car-parking system — and the fair is wonderful too. Admission £6, 11am- 5pm, 19-20 June, gilbertwhiteshouse.org.uk