The silhouette slung between two trees is unmistakable: a crescent moon, a daisy petal, a lazy smile — a hammock. The image is nostalgic in the way that we tend to file simple pleasures under the heading of "bygone times."

But 'mocking is what's happening right now.

Not only are hammocks a trend, they're also a verb, as in, "Wanna 'mock tomorrow?" or, in the guiding principle of a burgeoning movement called the Hammock Initiative: "When in doubt, hammock it out."

That's what Tess Linville and three girlfriends, all 14, do on pleasant afternoons — albeit without any apparent doubt — looping the straps of their featherweight nylon hammocks to the tracery of tree branches near Lake Harriet's rose gardens. If they get the right spot, they all can face each other, like sitting around an arboreal card table.

Last summer, they'd likely have been "in our rooms, on our phones, watching TV," Linville said. Now most of their friends own hammocks.

"You can pack it up so easy," said Paulina Delmont, who biked to the lake. They can spend hours talking or reading or, as Molly McChesney noted, "catching up on sleep you missed the night before."

Hammocks have been around for centuries. Columbus brought them back with him to Spain. Today's boost in popularity is driven in part by advances in technology.

Made of nylon, many hammocks now weigh barely a pound and scrunch up into packets the size of a sandwich bag. You can start swaying for less than $100 — but then may be tempted by the rain tarps, underslings for gear, bug nets and little battery-operated lanterns to hang within reach.

Little wonder that more hammocks are swaying on college campuses, parks and some hip offices such as Google and Buzzfeed. Swayers share tips (so to speak) on sites such as hammockforums.net.

There's even a group, the Hammock Initiative, or HI, founded last year in North Dakota. Yes, North Dakota, the state known for its absence of trees, although the group is based in relatively forested Fargo. Last month, more than 200 people convened for HI's first formal Sway Day, said founder Drew Spooner.

"I've been a big fan of hammocks since I spent time in Colorado working a trail crew," said Spooner, a 23-year-old marketing student. "Now I carry one in my backpack for emergency purposes. It's a fun, playful gesture, but a great way to relax."

Hammock Day for sway

July 22 is National Hammock Day. It's been around for a few years, although its origins are murky and therefore possibly retail-based. But why quibble?

The Minneapolis gathering will be from 4 to 7 pm. Wednesday at Lake Nokomis, where Minnehaha Creek meets the lake, east of Cedar Avenue on Minnehaha Parkway. Check the Hammock Initiative's Facebook page for updates.

Benjamin Davis is Minnesota's "hammbassador" and is organizing the event, although that term may overstate the goings-on.

"We're not too ambitious about it," said Davis, 25, a professional musician and president of the Minnesota Viola Society. "If you spend too much time and energy on this, that defeats the point."

Heed the Hammock Initiative's vision statement: "We want to see people gathered together for the purpose of relaxing, enjoying each other's company and, literally, hanging out. This vision may not sound audacious or ambitious, and that's the point. It's an opportunity for people to be, not do."

Davis knows that just "being" isn't always easy.

"Everybody's always doing, doing, doing," he said. "But if you stay home and just sit around, you feel as if you're not doing anything.

"The hammock is the perfect way to 'not do,' and yet you're doing something."

That's how Sam Klein and Anna Patterson described what, to the uninformed eye, looked like sloth as the 18-year-olds shared a hammock near Lake Calhoun.

"It's way more popular than last summer," Klein said of hammocking. He'll have his along when arriving at the University of Kansas this fall. "I think it'd be a lot more comfortable to use when you're doing homework or reading."

Klein said he most often likes to hang with other hammockers. "It's fun when it's a communal thing," he said. "But if you really need some alone time, a hammock is a good place to be."

Portability is a lure

Barb Anseth saw hammock sales start to rise about three years ago at the REI store in Bloomington, where she's sales manager. This year?

"It's really, really crazy," she said, with more interest from younger teenagers. "They're coming in with their parents, who are usually looking at me, like, 'What is this?'

"But then you get people in that age group who are going up to the Boundary Waters and are totally getting into it," she added. "It's all I can do stay on top of our inventory."

Eagles Nest Outfitters in North Carolina is the industry leader, touting hammocks that fit in bags "the size of a grapefruit." Wide nylon straps are meant to minimize damage or stress to tree bark.

The trend has spurred a debate about outdoor ethics. Several universities have banned hammocks from campus trees. Michigan State University singles out the slings for potential tree damage from the straps. That's prompted a campus hammocking club to propose hammocking "safe zones" or designating trees that are "strap-friendly."

Ralph Sievert, director of forestry for the Minneapolis Park and Recreation Board, said his staff hasn't seen any damage, but is watching to see if repeated use has an impact. If so, they'll likely begin educating park users about responsible hammock use, "but for now, we're just kind of letting folks enjoy the trees."

Anseth of REI said staffers encourage customers to choose more mature trees 10 inches or more in diameter. But they're also boosting their stock of hammock stands.

"Who knew this would be so big?"

Swaying in the moment

Spooner, known as the Chief of Sway in the Hammock Initiative, said that 'mockers often are motivated by the power of a warm memory.

"People would say, 'I got this on a mission trip to Honduras and haven't used it since,' or, 'I brought this back from the lake,' " he said. "And some have not-so-great memories of hammock tipovers, but we try to help them overcome this so they can hammock again."

The trauma of hammock tipovers is real — especially if you do an Internet search for "hammocks up high." Davis explained his technique, beginning with simply sitting in the hammock.

"First, get your tushie in there," he said. "Then arrange the back of the hammock so you sort of have a basin to fall into." Then lean back, pivot and bring in your feet.

"Like being rocked in your mother's arms," he said, and if there's a vestigial memory about such things, that observation probably is spot-on.

Davis tries to sway daily, either in his front yard or in a nearby park.

"I can't clock in and clock out of work," he said of his musician's life. "My work is me and my computer. But when I grab my hammock and go outside, I can shut that out."

Then he looked down at the front of his shirt. Slinging his hammock between two glorious pines, he'd also set himself up for nature's consequences.

"I was looking up and a drop of sap dripped on me," he said with a jokey grimace as he tried scratching it off. "It smells lovely, but it's really sticky."

He paused, then smiled.

"On the other hand, I was in a place where I could notice a drop of sap hitting me."

Kim Ode • 612-673-7185