Reefer Madness turned to Reefer Gladness in the Big Apple on Thursday, as thousands of stoners turned out in parks and performance spaces to celebrate the unofficial 4/20 holiday — the first annual fête since pot was legalized in New York.

But the weed-wonderland gathering under sunny skies in Washington Square Park, the past site of raucous “legalize pot” rallies, had all the thrills of a street fair that’s run out of tube socks.

I expected that the stoner hordes, flush with triumph, would turn the park into a hell-raising victory party.

But now that weed’s for sale on practically every block, the once impassioned event felt denatured, filled with hemp-lovers who had lost their spark. (Unlicensed sales can get dealers into legal trouble, but purchasers have no worries.)

FIT students Noelle D’Antuono and Sophie Browne, puffing merrily on joints they brought to the park, noted the almost too-laid-back atmosphere.

“Last year it was protest-y and messy,” Browne said.

“There were pizza boxes all over the ground,” she recalled of the 2022 event, sounding wistful.

But she noted it was still early.

“We’re going to stay into the night,” she said, with an anticipatory smile.

The air was shockingly fresh and smoke-free, unlike in previous years when a nuclear mushroom that could be smelled from a block away hung over the Washington Square Arch and the park fountain.

There was less acrid aroma than I often encounter walking under a sidewalk scaffold.

Afternoon merchandise sellers almost outnumbered smokers, peddling pot paraphernalia, books, cheap art, sneakers, “magic” oils, jewelry and Mexican shaved ice. 

Caricaturists and tarot card readers were on hand to provide their essential services, just like on any other day in the park.

In the almost annoyingly wholesome atmosphere, men outnumbered women three-to-one. Some visitors puffed, but many more munched on junk food alongside their boyfriends, girlfriends, families or dogs.

The closest thing I saw to a confrontation came when a hot dog buyer first mistook the posted 240-calorie count for $2.40.

The actual price was $4, which he coughed up without a struggle.

“Ain’t gonna fight it,” he laughed — which expressed the day’s mood.

Still, enough NYPD officers to cover Times Square on New Year’s Eve slinked from one sales booth to the next, quizzing vendors to make sure they weren’t actually selling pot without a license.

The picture-shy police seemed more bent out of shape by the presence of a working photographer than by drug-law violations.

One cop challenged The Post’s Brian Zak, “Can I help you? You’re following me around.”

Their time would be better spent poking their heads inside the park’s new public toilets, where Zak observed a man shooting up heroin, right in plain view.

In the absence (mostly) of actual marijuana for sale, there were oodles of gadgets to deliver a kick without lighting up.

Ashlin Simpson, from California, inhaled hash oil from an ENCO Disposable Vape Cup — one of scores of hard-to-identify instruments of inhalation.

Was it her first 420? “Noooooo,” she said with a laugh before she enthusiastically returned to the task.  

I braved a sniff of “platinum cookies,” a potent marijuana strain with a high THC level at a stand called Top Shelf. They looked like fresh white truffles and were almost as pungent, but in a flavor that’s too nasty for my non-stoner’s nose.

I finally took the plunge on a $20, marijuana-infused, chocolate-based “cookie monster” from L&T Sweets.

Tara, one of the owners, predicted, “You won’t eat the whole thing today.”

I soon learned why: The stuff kicked in when I was halfway through the cookie. It was delicious, too, a far cry from the execrable “dope brownies” of my college days.

Washington Square Park has seen worse days of crime, rioting and squalor. Things were so sleepy on 4/20, I almost missed the sound and fury of past marijuana holidays.

But not the smoke.