It’s not the holidays without Nat King Cole’s 1946 hit The Christmas Song blasting from your radio as you go to pick up your tree, and nowadays, that song might also remind you to pick up some mistletoe.

The strange tradition of kissing beneath mistletoe has withstood the test of time. The 19th-century American author Washington Irving wrote about the practice in one of his books, saying: “The mistletoe is still hung up in farm-houses and kitchens at Christmas,” documenting the ritual. “The young men have the privilege of kissing the girls under it, plucking each time a berry from the bush. When the berries are all plucked, the privilege ceases.”

Back then, the principal way to get mistletoe was by climbing up a tree, and hacking it off with an ax. But in 2019, you can walk right into Walmart, Trader Joe’s or your neighborhood garden supply shop and buy a nicely boxed swatch.

In modern times, Hallmark movies and the ever-popular Burl Ives Holly Jolly Christmas song are happy to remind folks of the usage of mistletoe.

“Oh ho, the mistletoe, hung where you can see. Somebody waits for you, kiss her once for me,” croons Ives in the song.

Triumph Oregon has been selling mistletoe for 20 years from Oregon. Recently acquired by Enroot Products and FibreDust LLC, the company sells mistletoe to Amazon, Walmart, Trader Joe’s and more than 250 other small garden shops, suppliers and distributors.

The plant is harvested in the forests across the north-western state, an annual process that is very labor intensive for the three to four weeks of the holiday season.

It grows high up in the trees, and laborers climb the trees, cut the mistletoe, then send to processor Trillium Gardens for cleaning and cutting into smaller pieces. The final product is tied up in a small bow, boxed and shipped nationwide.

“Anyone can go to Michael’s and buy a plastic thing, but people want to see a real product. It was actually alive,” said Enroot’s Andrew Pidgeon.

Enroot’s sales of mistletoe were up 10% last year, to 700,000 sprigs.

The orders start coming in as early as October, but the plants can’t be shipped until closer to the festive season – they can easily sweat and grow mold. Mistletoe is shipped a day after it’s cut to avoid that, and only for the four to five weeks around Thanksgiving to the New Year.

But even small-town retailers are getting in on the action. At Mistletoe Tree Farm in Massachusetts, owner Megan Krugger buys from another wholesaler in Oregon, usually around 200 swatches a year. “We almost sell out every year. Customers get their tree, and purchase a sprig of mistletoe,” she told the Guardian.

In Virginia, Amy Reese is a vendor at the Lynchburg Community Marketplace, a year-round farmer’s market and craft fair. Reese sells wreaths and mistletoe, retailing the plant at two to five dollars a bundle, depending on the size.

She and her children collect mistletoe by climbing trees or using lobbers, baskets with metal around them on a very long stick. She says it grows on oak and apple trees, among other hosts. “I tell people to get the one with the most berries,” she said. “You’re supposed to take one off every time you kiss someone. I find it fun.” The family ends up selling at least 100 bundles a year.

Her advice for prolonging the life of the plant is to put it in the refrigerator when it’s not in use to avoid molding, or to put a piece with the stems in water.

Mistletoe hasn’t always been for kissing. In Ancient Greek and Roman times, it was used to treat menstrual cramps, ulcers and epilepsy. Druids thought that the plant promoted fertility.

Some folklore says that in Norse mythology, the goddess of love, Frigg, secured an oath from all the animals and plants in the world that they wouldn’t harm her son Baldur, whose death was foretold. She forgot mistletoe, which another god used to kill Baldur.

He was eventually resurrected and a relieved Frigg proclaimed the plant a symbol of love meant to be kissed under.

The scientific name for American mistletoe is Phoradendron, which is aptly translated into Greek as “tree thief”. It latches itself, similar to a parasite, on to the branches of its host and takes water and nutrients out of it, often killing the tree. Mistletoe berries are toxic to humans, but birds ingest them, and spread the growth.

There are some concerns over how human-caused climate change will affect mistletoe, which is at the mercy of the health of its host tree. “There’s definitely less of it. This year we had issues on how much we could harvest, and increasingly, you have to go further into the woods to find it,” said Pidgeon.