A year or so ago, I gave a keynote speech at a Pinot Noir conference in Wellington, New Zealand. I don’t think that I’m going too far in saying that some of the points I made caused a bit of a stir.

One of them involved modern methods of growing Pinot Noir. Without wishing to rehash the matter, suffice it to say that I submitted that Pinot Noir producers in the New World use too few clones; that too often the clones are too narrowly chosen for flavor intensity at the expense of nuance (the so-called Dijon clones); and that the vineyards themselves are planted too “rationally.”

This last point was the one that seemed to stick in some people’s craws. A great Pinot Noir vineyard, I asserted, is one where there are 30 or 40 clones interplanted like wildflowers in such a way as to preclude picking each clone separately at “optimum ripeness,” as is regularly done when clones are “rationally” planted in separate blocks.

For many—although not all—this was a step too far. Give up control? Don’t be ridiculous.

I was surprised at the intensity of this response because, after all, what I proposed is what the Burgundians have been doing for centuries, what they call sélection massale, or mass planting: Cuttings are taken from a variety of vines in an existing (old) vineyard and its clonal/genetic mix is perpetuated by reproducing the vineyard’s lineage.

This approach works best in old vineyards where a “wildflower variety” of clones already exist. To achieve that effect in a brand-new vineyard means assembling as many clones or strains as you can and then, figuratively speaking, strewing them about.

You might be interested to learn that at least two wine producers I know have decided to experiment along these lines of “irrational” planting of numerous strains, both of them generously acknowledging that my presentation inspired them to do so. One is in California (Hahn Estates in Monterey County); the other is in New Zealand (Craggy Range Vineyards). Interestingly, both are sizable, highly successful clear-eyed-about-business producers, rather than the micro-loony one might expect.

All this came back to me forcibly as I looked down upon a small vineyard parcel in Portugal’s Douro Valley. I was standing there surveying the stunning landscape with Tomás Roquette, who, along with his brother, Miguel, owns and runs one of the Douro’s greatest estates, Quinta do Crasto.

“That vineyard down there is our greatest single plot, called Vinha Maria Teresa,” said Mr. Roquette. “And we are very concerned here in the Douro that what that vineyard has—and others like it elsewhere—must be preserved for the future. The biggest mistake we can make here in Portugal is to be ‘varietal,’” he added, making quote marks with his hands to emphasize “varietal.”

This is no airy philosophizing. The Roquette family has engaged university researchers to genetically identify every grapevine in the 11.7-acre Maria Teresa vineyard. “The vines in Maria Teresa are all at least 100 years old,” said Mr. Roquette. “Some are probably 120 yeas old, but we can’t prove that.”

“What we know for sure is that the wine we make from Maria Teresa, which we bottle separately in the best vintages, cannot be seen as anything other than the whole of the vineyard itself. You would call it a field blend. But really, it’s much, much more than that. It’s like the vineyard is one integrated being, if that makes any sense.”

With the use of high-resolution satellite mapping and the genotyping performed by researchers, the goal is to create a Maria Teresa “gene bank,” a kind of viticultural Noah’s Ark.

“So far, we have identified 47 different grape varieties in this 4.7-hectare plot,” he continued. “There are 36 different red varieties, nine different whites and even two rosés [Alicante Espanhol and Ferral Roxo]. We have to preserve it at all costs, at least if we want to create what we, anyway, think is greatness.”

The project, which is not yet complete, is to first genetically identify each individual vine and then, in a different location, reproduce that specific genetic expression so that it will be available when needed.

“We will have a map that shows every grapevine by genotype, identified as, say, Row 27, Grapevine 33. When just one vine dies or has to be removed, we will be able to replant that vine with its exact genetic duplicate. If we don’t, then the wine we know today as Maria Teresa won’t exist tomorrow. And that would be a huge loss.”

Living in Portugal has powerfully reinforced my increasing sense, as a taster as well as a professional observer, of the need to broaden our overly simplistic notion of “varietal.”

“Portugal has a phenomenal number of indigenous varieties,” said Jorge Rosas of the Port producer Ramos Pinto. He feels a personal connection to this matter of indigenous varieties because his father, José António Ramos Pinto Rosas, helped create in 1982 a non-profit research organization called ADVID (Association for the Development of Viticulture in the Douro Region) that has been actively involved in identifying vines and strains.

“In the Douro alone we have 64 red grape varieties and 47 white grapes—so far. And they’re all interplanted,” noted Mr. Rosas. “In all of Portugal, we’ve so far identified 280 indigenous Portuguese grape varieties. But there’s surely more than that, because the work is far from complete. I mean, we’ve so far identified 197 clones just of Touriga Nacional!”

Seeing and hearing all this, to say nothing of tasting, has brought home to me not just the desirability of preserving the world’s array of indigenous varieties, but of catapulting ourselves from an over-reliance on “varietalness.”

Sure, Pinot Noir likely is best presented in solitary glory, but how many grape varieties are truly complete in themselves? Nebbiolo perhaps. (I once wrote that blending Nebbiolo is like putting Pavarotti in the chorus.)

What Portugal has taught me, if nothing else, is that “indigenous” doesn’t mean merely a pinpoint recognition of just one local grape (however necessary and useful that identification may be), but of the reality—the necessity, even—of a vineyard mosaic.

That’s the key word—mosaic. It could be a matter of a mosaic of many varieties. Or a mosaic of many clones or strains within a single variety. But somehow, in some fashion, a multiplicity must be present among the vines.

Without that, we will surely lose our grasp on nuance, shadings, even greatness, don’t you think?