In the wine world, some grapes and regions ebb and flow in popularity. New Zealand sauvignon blanc comes on, and Australian shiraz goes away.

One category that's immune to such gyrations: red blends. These wines "are a stable platform," said Christian Nesheim, owner and wine buyer at Vini­fera in Plymouth.

Truth be known, most red wines are blends. The great Châteuneuf-du-Papes of the southern Rhone are all blends, as are most of Bordeaux's reds.

The nebbiolos of Piedmont and the pinot noirs of Burgundy and Oregon (but not California, where some vintners toss in some syrah, and it shows) are among the few 100 percent varietals. Some high-end Tuscan sangioveses and California cabs are all one grape, but many of them have other varieties added.

These wines can be called by the grape name as long as they contain 75 percent of said grape. Not so for "true" blends: the GSMs (Grenache-Syrah-Mourvedres) of Australia and France's Languedoc and Rhone regions, those increasingly popular reds from Portugal with the unfamiliar grape names and, most of all, the ripe reds coming out of California.

In recent years, Nesheim said, many customers have been asking for red blends rather than saying, "I need a pinot." Typical buyers fit no particular demographic, he said, but include mostly "people who want something not with dinner, but more drinkable to sit around the patio, something they can quaff."

The rationale behind these wines is that certain grapes can complement others, often by "filling in the holes" or shoring up weaknesses in color, structure or flavor.

The most popular of these "friendly wines," as he calls them, tend to be lower on tannins and acidity and long on ripe fruit. The prototypes: Menage à Trois (zin, cab and merlot), Apothic (syrah, zin, cab and merlot) and Marietta Old Vine (zin, petite sirah and more). These are fairly simple pleasures, showcasing grapes picked at peak ripeness, with chocolate notes and zinfandel's spice on display in each of them.

At similar prices, Reata's Whiplash "Redemption," Pedroncelli's "Friends," the Shebang! "Seventh Cuvee" and Bogle's "Essential" Old Vine are well worth checking out.

Quite a few other under-$20 red blends deliver bang for the buck: Columbia Winery's "Composition," Stephen Ross' Flying Cloud "Aviator" (named after the Eden Prairie airport), McKinley Springs' "Horsepower," Michael David's Petite Petit (petite sirah and petit verdot; get it?), Waterbrook's "Melange," Clif Bar's "The Climber" and Dr. Thurston Wolfe's "Doctor Wolfe's Family."

There's more on the way: After developing a cult-like following for his $30-plus "The Prisoner," vintner Dave Phinney is out with a trio of "Locations" blends labeled F (for France), I (Italy) and E (España/Spain) in the $17 range. They are approachable and true to their origins; those liking more acidity in their wine should say "I."

As usual, spending more will get you more. Bonny Doon's "Le Cigare Volant" and Tablas Creek "Esprit de Tablas" (formerly "Esprit de Beaucastel") are well worth the $45 to $50 price tags for those willing to spend that much. And Shafer's always-superb "Relentless" ($72) earned Wine of the Year honors from Wine Spectator in 2012.

That wine used to be called a syrah but now bears no varietal labeling and includes a healthy dollop of petite sirah.

Even the best wineries know when it's time to go to a blend.