A little before noon on Oct. 5, Richard Morrison was hanging a glass ornament that resembled a head of garlic on a small metal tree. It was one of several trees that had been installed inside a John Derian store in Manhattan’s East Village neighborhood, where Mr. Morrison, a floor manager, and his colleagues had been setting up holiday décor since Sept. 30.

It was the earliest that John Derian, 61, had begun the Christmas season at his store since he started his namesake retail business in New York in 1995.

Mr. Morrison, 36, was one of five employees unpacking and arranging ornaments at the shop on Oct. 5, a balmy Thursday. As he hung the ornament, he wiped a streak of glitter from his brow. “It’s a hazard here,” he said of the glitter. Claire Cook, 28, a store manager who was also decorating, added, “If you work here, you can’t be bothered by glitter.”

Mr. Derian, who owns three stores on East Second Street, not only started the season earlier than ever this year, but he also dedicated more space than before to holiday décor by turning a shop normally used as a furniture showroom into a festive wonderland. “People don’t buy furniture as Christmas gifts,” he said, “so I thought it might be fun to do it in here.”

Inside are a dozen trees bearing hundreds of ornaments, along with wreaths; vintage garlands made of glass; papier-mâché tree toppers; and a giant snowman named Tony that Mr. Derian bought from an antiques dealer in Rhode Island. He paid about $1,200 for the snowman, he said, adding that if a customer wanted to buy it, he would charge around $2,400.

But on Oct. 5, the day before the holiday shop opened to the public, it was still in disarray. Around 1 p.m. that afternoon, a young woman wearing a blush-colored athleisure set walked in as “Over the Rainbow” by Judy Garland was playing.

“We are actually not open,” Mr. Morrison told her, “but feel free to look around. Just be careful!”

A group of Angel ornaments in blue and pink pastel shades hung from copper meat hooks near the register. Cardboard boxes strewn about the shop contained even more ornaments: Pickles, mermaids, artichokes, caviar tins, corgis, oysters, vegetables and toadstools were just some of the designs. Most were made of glass in Poland or Germany. Their prices vary: A small glass peacock ornament costs $32; a large glass dragon costs $352.

As the young woman left the shop, her L.L. Bean tote bag, embroidered with the word “slay,” barely missed a peacock.

Mr. Derian said that he had about 50,000 ornaments for sale online and at his stores this year. Employees try to keep three of each style on display. As ornaments are sold — or broken — they are replaced. Some extras are stored in a courtyard behind the holiday shop for easy access. Others are kept down the block, at a space used for shipping and storage, and at a studio on Chrystie Street where Mr. Derian makes decoupage, a type of cut-and-paste art.

Mr. Derian estimated that a couple of ornaments were broken each day at his stores, but there is no you-break it-you-buy-it rule. “When someone breaks an ornament, we say an angel gets its wings,” he added, referring to a line from the film “It’s a Wonderful Life.”

Several were destroyed as the shop was being set up on Oct. 5. Their shattered remains were tossed into a box that the employees called the “ornament graveyard.”

“Every once in a while you hear a crash and hope for the best,” said Patrick Dugan, 36, a sales associate helping to decorate the shop.

Near the back of the store, a towering artificial spruce tree dappled with fake snow was being adorned with fungi ornaments of various shapes in colors like red, green, purple, pink and aquamarine. Many employees said that the mushroom tree, versions of which have been set up in past years, had become the most popular holiday display.

Piotr Morawski, whose family’s business, Morawski Ornaments in Lodz, Poland, has been selling items to Mr. Derian for about a decade, called him “the mushroom guy.”

Mr. Morawski, 29, added, “He loves them.”

Mr. Derian said his fondness for fungi grew after he began foraging for mushrooms in his spare time, adding that he has typically used what he has found for decorating, not for cooking. “You can forage your own mushrooms here,” he said of the shop, with “no ticks.”

He started selling ornaments 15 years ago because of his love for Christmas, he said, “and it just kept growing and growing.”

The actress Amy Sedaris, a longtime customer and now a friend of Mr. Derian’s, likened the inside of the holiday shop to “the bottom of the ‘I Dream of Jeannie’ bottle.” Anna Wintour, the Vogue editor and another longtime customer, said in an email, “There’s always something surprising or whimsical or amusing.”

Certain people have made a tradition of visiting Mr. Derian’s stores this time of year, he said, and some bring their children. He added that collaborations with Target, for which he recently designed a line of Thanksgiving décor, had brought him more exposure. “It turned into something that I didn’t expect it to turn into,” he said.

A newer element of Mr. Derian’s holiday setup is the rope stanchion he has used on East Second Street to limit the number of customers who can shop at a time. He started using it in 2020, when pandemic-related restrictions set strict capacity limits on stores. But he has continued to use the stanchion, he said, because “if you have too many people inside, it isn’t fun for anyone.”

Sometimes, especially on weekends in December, a line forms outside. At first, Mr. Derian said, “I would feel bad about the line.” But then he started noticing the lines that can form nearby on Lafayette Street outside Levain Bakery and the clothing store Kith. “I would go over there and there are lines and people are fine,” he said. “It’s a neighborhood of lines.”

Mr. Derian, who was raised in Watertown, Mass., and whose father managed a local supermarket, does not use point-of-sale software at his stores. Prices are written on paper tags and customers are given handwritten receipts. “I’m a creative person running a business, not really a business person,” he said, adding that he has been having online meetings with a business coach since 2022.

He said that around a quarter of his stores’ sales were holiday related. As in years past, he is opening some stores, including the holiday shop, for the season on Sundays, when they are normally closed. Mr. Derian also hired five seasonal workers this year. He employs about 40 people full time, and also has stores in the West Village and in Provincetown, Mass.

He thought that starting the season earlier and converting the furniture showroom into a holiday shop would help increase sales, he said, and offer a better shopping experience, in part because he is using a larger space. “It’s easier to get in and out of,” Mr. Derian said.

On Oct. 5, just after 2 p.m., a cloud of smoke appeared outside the shop’s entrance as the employees were preparing its displays. The smoke was wafting from a bunch of sage leaves lit by Thomas Little, whose company, Urbangreen, has done landscaping and planting work at Mr. Derian’s stores for the last decade.

Mr. Little, 59, said he began every project for Mr. Derian with a saging ritual.

“When you enter John’s,” he said, “it’s a sacred thing.”