This post has been updated. It was originally published on December 28, 2020.

When you set up a Christmas tree, you bring a little bit of nature into your home. Real or fake, your spot of green creates warm holiday cheer at a time when the forests outside have grown cold and brown.

But once you’ve unwrapped the presents, scarfed down the leftovers, and safely stowed away the ornaments, your glorious display piece instantly transforms into waste—specifically, one of the biggest pieces of trash you’ll have to deal with all year. How we collectively disperse the carbon, metal, and plastic that went into our trees makes a real difference for the environment that provided those resources in the first place.

Take artificial trees: Producing one of these contributes about 40 pounds of carbon dioxide to the atmosphere. The key to making it sustainable is to reuse it. By spreading that 40 pounds out over a certain number of years—estimates range from five years to 20—it eventually will break even with the smaller impact you would see from buying a new natural tree year after year.

So, if your tree is fake, your mission is simple: Box it up and save it for the next year. And the next. And the one after that. Bequeath it to your children and make it a family heirloom. When you finally need to get rid of it, do your best to recycle or donate it. Your local Goodwill is a good place to start.

[Related: How to pack and ship plants across the country]

However, lots of those boughs aren’t artificial. Of the 94 million Christmas trees estimated to be displayed in American homes this year, a whopping 14 million of them were real. And this has a positive effect. For example, most trees come from farms these days, so buying natural encourages short-term reforestation. More important, each one contains about 20 pounds of planet-warming carbon dioxide it removed from the atmosphere over the course of its lifetime. And once the carbon is out of the air, you want to avoid putting it back in. It may be an aspirational goal, but keeping all that carbon locked up in the wood would do as much for climate change as getting more than 27,400 cars off the road for a year.

Do a good deed at the end of this holiday season by making sure those greenhouse gases stay where they belong.

DO: Recycle your Christmas tree and turn it into mulch

Christmas trees represent one of those rare cases where the greenest disposal method may also be the easiest. Mulch might be the ideal fate for your tree because much of its carbon remains trapped in the wood, where it can return to the soil. And, if you live in an urban area, you probably have access to a public works department that will gratefully take your tree and turn it into useful woodchips for gardens and parks.

For example, the New York City Parks will be celebrating their annual Mulchfest until January 9 to do just that, and trees left on the curb between January 6 and 15 will end up in similar places.

Home Depots across the country also recycle trees—just remember to first call your local branch to confirm. Or search Earth911′s database by zip code to find a tree recycling program near you. If those options don’t help you, you can also check out this state-specific advice for recycling methods.

Wherever you bring it, remove all ornaments, lights, tinsel, nets, angels, and so on before dropping off your tree. These objects will not help gardens grow and pose a danger to animals.

DO: Let it become an animal playground

If you don’t have access to an urban recycling program, fear not. Trees are, by definition, biodegradable, and animals love conifers whether they’re alive or dead.

Drop your tree off in a forest and return it whence it came. Stick it in your backyard for birds to enjoy. You can even chuck it into a pond or lake and revitalize your favorite fishing hole—although you might want to check with your local fish and game department first.

[Related: Should you leave food out in the woods?]

Or, if you live near a zoo, ask if they’d like a large toy for their big cats. Lions and tigers reportedly react to Christmas trees the same way their smaller cousins respond to catnip, and will bat around the branches for hours.

Just make sure to strip off all the ornaments, lights, and particularly mistletoe before you give up your tree. These can choke or poison any animals that try to consume them.

DON’T: Burn your Christmas tree

Christmas trees make bad Yule Logs. Their flammable oils will coat your chimney with creosote and increase your risk of a fire. Burning it also sends the tree’s carbon back into the atmosphere, making burning a naughty choice indeed.

DON’T: Let it end up in a landfill

Of all the places a tree can go, a landfill is the absolute worst for the environment. While trees do break down naturally, a lot of municipal trash ends up underground where there’s little oxygen. The bacteria that thrive in these places tend to turn the carbon in waste into methane, which does more than 20 times as much damage to global temperatures as carbon dioxide does.

Before you let trash-collection pick it up, check with your local sanitation department to find out what they plan to do with your old Christmas tree. For example, some areas have a window of time when they’ll mulch the plants, as recommended. But if all else fails and you end up bringing your tree to a dump, try to make sure it ends up above ground.

In the grand scheme of things, Christmas trees are far from the planet’s biggest problem. But if we all get in the habit of guiding our trees toward environmentally-friendly destinations, at least we’ll be taking a step toward keeping future trees green, and future holiday seasons merry.