Pearls of wisdom: discovering the UK's exceptional native oysters

Watching Helio Garzon handle an oyster is like eavesdropping on a romance. As he holds one out for me to see, cradling the gnarled shell like the hand of a lover, his Latin American accent flares with affection.

"I can tell the age of an oyster just by looking at it," he says, tracing the growth rings of the shell with the edge of his knife. "See. Like the circles in a tree. This has been in the water three years." Then, sliding the knife in and under – killing it softly – he twists and cracks it open, revealing the glistening, plump oyster meat within. All love affairs, it seems, must come to an end.

Not so for Garzon, the master shucker of Bentley's oyster bar; the tryst between man and mollusc has lasted over 50 years, and Bentley's itself has been dishing out the decadent delicacy for 100 years this month.

September marks the start of Britain's oyster season and I've come to Richard Corrigan's fishy outpost to learn the art of going native. There are oyster fisheries all over the UK, with beds in Cornwall, Devon, Dorset, Kent, Essex, Scotland and Ireland.

Each oyster has a different taste, body and nose depending on their environmental conditions, or terroir – merroir, if you want to get fancy. For example, oysters from the River Fal bloom with notes of melon and cucumber before easing into a metallic finish, whereas Loch Ryan oysters are meaty and earthy, culminating in a tuning-fork tingle of iodine.

Native oysters from the same body of water can differ wildly when it comes to taste

Even oysters that are from the same body of water can differ wildly depending upon the location of their bed. As Wright Brothers' Robin Hancock says: "Oysters take their flavour from the environment that they're grown in, and with such variations of minerality and salinity we have wonderfully diverse-tasting oysters in the British Isles."

When we think of oysters, we might think of the devilish Casanova scoffing 50 for 'sexfast', or 'the world's mine oyster', a line borrowed from William Shakespeare's The Merry Wives of Windsor. And when we eat oysters we often eat 'Pacifics' (a nod to the species' original home in the warmer Pacific waters), otherwise known as rocks.

While natives (ostrea edulis) are smaller, lighter and with smoother shells, rocks (crassostrea gigas) are larger, heavier and rougher to the touch. Both kinds thrive in British waters, but since the rock's introduction some 30 years ago – ironically intended to boost native stocks – the adopted and artificially grown oyster has risen to prominence.

Cheaper to farm and quicker to grow, they can be ready to eat in two years compared to the native's three or four. They're also hardy little so-and-sos, as seventh-generation oysterman Richard Haward, of West Mersea Oysters – whose family have been plucking native oysters from the Blackwater in Essex since 1798 – explains: "The first thing a native thinks of doing is dying," he says. "It doesn't like extremes in natural conditions. Too much heat, too much cold, too much of anything. Whereas rock oysters don't take any notice. Their mortality rate is very low and they breed prolifically."

As a result rock oysters are farmed, sold, and consumed all year round. The native oyster, however, is only available from September to April (all the months with 'r' in their names). Haward asserts that the best time to eat your first native of the season is in November, once stocks have had a chance to rest in the cold water and plump back up after the summer's spawning has left them "skinny and milky" (and, although OK to eat, aesthetically undesirable for most).

This slower method of production is the key to the natives' superior body and taste. Oysters feed by filtering water through their system – the greedy beggars can get through up to ten litres per hour – and their flavour develops as a direct result of the minerals, salinity, and algae types they eat. And the longer they filter, the better the flavour.

In fact, even land run-off can impact the way an oyster tastes. That metallic tang of the Fal oyster described earlier? That comes from the tin mines on the Cornish coast. Talking of which, Chris Eden, Michelin-starred head chef at the Driftwood Hotel in Portscatho, believes the lesser-known Port Navas native – which tastes of "sweet brine and seaweed marine" – should be a treated as a seasonal great in the same way that asparagus, peas and Cornish new potatoes are.

Andrew McLay, head chef at seafood mecca J Sheekey – a glistening pearl in the urban oyster of Covent Garden – feels similarly about the West Mersea of Colchester because it's "nice, plump and earthy, and just a good oyster." He also acknowledges that it won't be everyone's cup of char. "If you had six different native oysters in front of you, you'd be able to taste the difference between the six. But taste is down to the individual and you should try more than one variety."

There is, however, one thing he is certain on: how to taste them. As a general rule of thumb, once shucked, an oyster should be sniffed (it should smell of the sea), sipped, and then tipped up until the meat slides out of the shell and into your mouth. It may need persuasion to leave its home with a fork.

When it's in your mouth, however, the advice varies. Garzon says you should always push the oyster against the roof of your mouth with your tongue to make sure that it's solid and flavoursome, as bad oysters will instantly reveal themselves with an acidic taste. He then says the oyster should be swallowed whole.

Hancock recommends a few chews to release the juices and let the complex minerals swim around the mouth, and McLay agrees: "Swallow an oyster whole and you don't get the whole experience," he says, adding that natives should always be eaten au naturel, with a pinch of black pepper and a squeeze of lemon if needed.

Back at Bentley's, I take his advice, swigging down a West Mersea for the first time. It smacks the chops with a salty kiss before mellowing to a meaty sweetness, leaving a pleasing sea scent lingering at the back of the throat. I can almost feel the sand between my toes, and the sun on my skin. I am blissed out on the beach.

Garzon nods sagely. "An explosion of happiness," he says – and there's romance in his voice once again.