Thanks to Omaze for supporting this video. To support a great cause and give yourself the chance to win a Tesla Model X Plaid, go to omaze.com/scishow.

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Trees come in all shapes and sizes, but as different as they are, you probably know a tree when you see one. Our definition of tree is actually pretty wishy-washy.

But whether you're in the tropics or a boreal forest, it's generally some tall plant with a leafy crown and a bunch of branches on a thick, woody trunk.

But some of the things we call trees aren't so tree-like at all. They're actually relatives of grass, and while many grass relatives get away with moonlighting as trees, there are a few tell-tale features that will expose these trees' grassy roots.

Picture the most famous and wide-ranging of all tropical trees: the coconut palm. These trees can grow over thirty meters tall, and their strong trunks are used to build bridges and homes.

But the truth is, the coconut palm is actually more closely related to the turf on your local soccer field than to any kind of woody tree, and one tell-tale clue is in how its seeds sprout.

When the seed of a coconut palm sends up its first shoot, it has a single leaf on it, and that's important because when we're talking about grass-like plants we're really talking about a large group of flowering plants called monocotyledons, or monocots for short.

A cotyledon is the first embryonic leaf that forms in a seed, and as the name suggests, monocots only have one of them. It's a feature that all grass relatives have in common, including plants like lilies and asparagus that don't look much like grasses but are all monocots.

On the other hand, many common trees like oaks, maples, and sycamores are so-called dicotyledons, or dicots. That's because they have two of these seed leaves.

But even if you're not around to witness a tree's first moments of life there are other ways to spot a tree that's actually related to grass, and one big clue can be the trunk.

Most tree trunks have an outer layer of protective bark and underneath they have woody tissues transporting sugar and water. These trees produce a new layer of those tissues each year, which is why if you look at any woody tree stump or sawed-off branch you'll see those signature tree rings that reveal its age.

But not all trees that look woody actually are. For example, certain types of bamboo can grow into dense, towering forests and these plants can have really strong, hard trunks, but their structure is dramatically different from the trunks on most trees.

Instead of growing outward by adding a new layer to the trunk each year, bamboo trunks only grow up. They're made up of a series of hollow shoots connected by nodes.

So even though bamboo evolved to have a strong, thick trunk, its growth pattern is a dead giveaway that it has grassy origins. Still, some monocots have trunks that look a lot like the typical woody tree trunk, so at first glance it's harder to pinpoint their origins.

But in these cases, the roots often reveal the truth. For instance, one type of palm tree that grows in the Amazon Rainforest has a trunk that looks pretty average and woody, but the roots are unusual.

This tree grows large, straight roots that emerge directly from the trunk, and they're made of regular plant tissue, unlike most tree roots which are made of a specific kind of tissue that's only used to make roots.

And instead of growing and branching out deep underground like the root systems on most trees, these roots often grow higher up on the trunk and stay in shallow ground.

These exposed roots can continue to transport gases and nutrients when the soil is completely waterlogged, so they help the tree cope with frequent floods. And they also point to this palm tree's grassy origins because this type of root system is typical of monocots.

Finally, if the trunk and roots don't give away a grass disguised as a tree, one other place to look for a clue is in the branches. A lot of monocot trees like bamboo and palm trees show no real branching despite growing a tall, strong trunk.

But some grassy trees have evolved to be so tree-like that it's very difficult to suss out their grassy origins at first glance. The so-called Dragon Blood tree, found only in Yemen, checks all the normal tree boxes: it's got a thick trunk, smooth bark, and yes, even a wide branching leafy canopy.

It even has growth zones that resemble the tree rings of woody trees, but its genetics reveal that even this tree is a monocot; it has just evolved many of the same traits as ordinary trees.

Which raises the question of why all these grass relatives are now living their best life as trees, and what it comes down to is the fact that being a tree has a lot of perks.

For one, growing tall means better access to sunlight. Thick trunks also add strength and stability and can help plants live longer. Plus, trees are great at enduring short-term stresses like droughts and floods.

And since they're so good at surviving, trees have evolved many times. They don't have one single evolutionary origin. So sometimes when you're looking at a tree, you're looking at a monocot, other times a dicot, and trees like pines and cedars are neither, but are definitely still trees.

And that's simply because trees aren't a taxonomic group. It's more a loose term we apply to plants that just kind of look the same.

So there are many distantly related plants that we call trees, and that includes some pretty incredible relatives of the grasses.

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