When it comes to decorating Christmas trees, science does not offer as much guidance as one would like. Pop the words “Christmas tree” or “Christmas tree decoration” into Google Scholar’s search box, and you’ll be regaled with a pile of patent applications for new fairy lights models, or worrisome studies on fir and spruce farmers poisoned by pesticides. Not a word on what’s the best way to efficiently arrange your lights, baubles, treetops, and tinsel.

One of the few attempts at dealing with the matter in an even vaguely rigorous way dates back to 2015, when a group of maths students at the University of Sheffield proposed a formula for calculating the ideal amount of baubles and tinsel, and the treetop’s dimension, depending on the tree’s height. According to the formula, a 152cm (five foot) Christmas tree would need 31 baubles, around 776cm of tinsel and 478cm of lights with a 15cm star or angel to top it off.

That is about 6.2 baubles per foot of Christmas tree (30.4 cm). If you ask Thomas Harman, founder of artificial trees and Christmas decorations manufacturer Balsam Hill, that is about right. Harman, who is based in California, says that depending on the tree’s diameter, the ideal amount of bauble-per-foot varies between ten and 20 and five and ten.

“In the UK, the diameter of Christmas trees tends to be smaller [than in the US],” he says. “So I’d say you’ll need between five and ten baubles per foot.”

Of the two most popular Christmas tree species in the UK – the Norway Spruce and the Nordmann fir – the latter tends to have a larger diameter than the former, thus requiring more baubles. Harman’s recommendation assumes the baubles’ diameter to be about eight centimetres (three inches).

Harman’s suggestion applies to reasonably-sized trees. If you are dealing with prodigiously huge vegetals, you’ll need quite a lot of extra baubles. Take the 13-metre-tall, 5.5-metre-wide tree towering in Las Vegas’ Bellagio Casino. “There is an ideal baubles-to-lights ratio we adopt: about 75 ornaments per foot. Since trees are wider at the bottom than the top, there will be more ornaments placed toward the base than there will be at the top,” says Jerry Bowlen, Bellagio’s executive director of horticulture. “The light ratio we use at Bellagio is 160 lights per foot.”

Eros Buogo, who is in charge of decorating a 33-metre, 200-year-old Christmas cedar at the Castel Brando hotel near Treviso, northern Italy, says that the tree is decked out with twenty 30-metre-long fairy light strings, adding up to 600 LED lights. It was important, he says, to space the lights about one metre apart.

Of course, the level of garishness and complexity befitting a Las Vegas resort or an Italian manor might not be what you are aiming for with your home tree. For domestic settings, you’d want to stick with Harman’s suggestion of about 100 fairy light per foot. “So if you get a six-foot [182cm] tree, you’ll need 600 lights on that tree. That’s a very standard rule in the Christmas tree industry.”

Harman also suggests tying the lights to the tree with some wire, rather than winding them around the branches. “You can just wrap lights like a scarf around the tree, but then it kinda looks like an Egyptian mummy. What’s nice is to work the lights from the inside, out the branches and then back in, and use some florist wire, better if green.”

And if you opted for a real tree, you will have to make sure it stays alive as long as possible. Harman suggests cutting the tree’s trunk open and putting it in a water basin as soon as you get home. That will keep the tree alive.

“An interesting technical detail is that the tree sucks water up into the trunk during the day, and it lets it out down at night,” Harman says. “That is why you want to water your tree ideally at night, when the water is back down. If you water it during the day, the water might spill out at night.”

However assiduous you are in your watering, though, Christmas tree can only survive so long. Harman says that the usual lifetime is of around three weeks, but that many people keep the tree up for over six weeks – an error that can transform the mirthful Yuletide fixture into an infernal fire hazard.

“When the tree starts to dry out, you have to be very careful with electrical equipment on the tree,” Harman says. That is why going artificial can sometimes be the right choice – at least for the UK’s numerous country squires.

“If someone who lives in London has a house in the country, and they go back and forth through the holidays, and they don’t have a butler to water the tree, an artificial tree is better for safety,” Harman says. No butler to water the tree? Be careful. Even the perfect ratio of lights can turn into a fire hazard.

Source: Wired