On a recent Sunday morning, Matt Lightner, the bespectacled 29-year-old chef of the heralded Castagna Restaurant in Portland, Ore., was hunched over a bed of salicornia at Netarts Bay on the Oregon Coast. Salicornia, also known as pickleweed, is a salty-tasting succulent that grows like a weed — wait, it is a weed! — in marshy, brackish areas.

Lightner was leading a foraging field trip of sorts. He introduced the assembled group of foodists to Lars Norgren, a towering figure with a mop of unkempt gray hair and an encyclopedic knowledge of wild plants.

“This is a salt-marsh species of lamb’s quarter,” said Norgren, surveying a plot of salicornia. “You could flood the Portland market for several years with this little … what is it? An eighth of an acre?”

Norgren often accompanies Lightner on his gathering forays, steering him clear of Destroying Angel mushrooms and hemlocks and singling out oddities like an orange parasitic vine called dodder. Though he was once a full-time wildcrafter (he dislikes the term “forager,” preferring “wildcrafter” or “picker” instead), these days Norgren spends most of his time buying wild edibles from local pickers and selling them to Portland restaurants such as Castagna, EVOE, Le Pigeon and Nostrana via his company, Peak Forest Fruit.

“Matt is typically ordering things that nobody else buys,” Norgren told me.

Salicornia is still a marginal item, even in local-foods-obsessed Portland, where Norgren sells it at the Hollywood Farmers’ Market. Lightner uses a few sprigs of the raw plant on a dish of sea urchin, caramelized beets and black-garlic puree.

“You want to get this idea that you’re in the ocean,” Lightner said. “The salicornia is really crisp and livens things up.”

As unlikely as it sounds, foraging is hot. A recession-friendly habit — what could be cheaper than picking weeds for your supper? — it is also a logical (if extreme) extension of the local-foods movement. Slow Food chapters across the country are touting foraging walks; companies such as the botanist John Kallas ’s Wild Food Adventures run sold-out edible-plant workshops and clam digs; and community gleaning organizations are popping up like mushrooms from coast to coast.

But while high-end restaurants have long featured chanterelles and ground cherries on their menus, not many chefs actually take time out of the kitchen to harvest for wild ingredients themselves.

Lightner’s passion for foraging grew out of the time he spent in the Basque region of Spain, apprenticing with the chef Andoni Aduriz at the Michelin-starred Mugaritz. Aduriz and his team of foragers there collect mushrooms, flowers and wild plants in the hills surrounding the restaurant. (Lightner also spent a month working at Noma in Copenhagen under Rene Redzepi, who is also known for getting his hands dirty.)

During peak foraging times, the chef is in the forest as many as three times a week. “It’s not necessarily the coast,” he says, alluding mysteriously to fruitful groves that are closer to Portland.

Back on the coast, he and Norgren led their retinue into a moss-covered forest on the side of the road.

“This here is a sword fern,” Norgren said. “It puts up very impressive fiddleheads, but it’s seriously bitter. You get people who say ‘fiddlehead ferns,’ and there is no such species as fiddlehead ferns. It’s a stage of every fern!”

Norgren first pointed out an evergreen huckleberry bush and a chicken of the woods mushroom: “Within a couple of days of it appearing, it’s inedible; it goes from being as tender as raw meat to tough as cardboard!” He then gestured to a mat of oxalis, or wood sorrel, which Lightner was already busily collecting in a flat Tupperware container.

Wood sorrel, which has three heart-shaped leaflets (it’s often mistaken for a clover), has a sour flavor — and three times the level of iron found in spinach.“We use it for a lot of things at the restaurant, from desserts to savory dishes,” Lightner said. “It’s acidic, so it goes well with tartares and things that could use a little sour flavor.” Wood sorrel is also abundant in Portland: it grows in yards, parks, even on the side of the street. Not all Portlanders can swing a meal at Castagna, but they can pluck wood sorrel from their own backyard.

Fifty years ago, wild mushrooms were as rare on Portland menus as salicornia is now. (According to Norgren, chanterelles fetched just 15 cents a pound back then.) Though salicornia likely won’t gain the same foodie status as chanterelles any time soon, Lightner’s innovative use of these local weeds — elevating dishes with a crunchy texture here and a sour flavor there — is exposing Castagna diners to the riches in their own backyards.