Letter From the Desert: Joshua Trees are Trees

That thing you heard is wrong.

Joshua tree, emphasis on the fourth syllable. Creative Commons photo by Ken Lund

I mean, I get it. I understand. You’re writing, or talking, or singing about an increasingly popular desert plant, and there’s this thing you heard that’s quirky and somewhat counterintuitive, and it’s always fun to drop such things into what you’re saying. It’s a way of being interesting. And it’s a relatively benign practice, sometimes even a wholly positive one, though it does get done to death to the point where it’s made fun of. “The Holy Roman Empire was neither holy, nor Roman, nor an empire. Discuss.”

Interesting fact: the word “neither” is used wrongly in the previous sentence! See, I get it.

At any rate, it’s completely normal to enjoy sprinkling your conversations about Joshua trees, whether those conversations are written or spoken, with quirky, counterintuitive statements. When you’re excited about a topic, whether Joshua trees or anything else, it’s fun to share the details, especially if you think they’re surprising.

But you know, sometimes statements are counterintuitive because they’re wrong.

Ben Maas @masbenMaas

Ummm. A Joshua tree is not a tree. A Joshua tree, called Yucca brevifolia, which is a plant that belongs to the genus Yucca. A tall, pokey plant, basically. Yucca brevifolia is tree like in it's shape, which is where the confusion commonly arises. They are still cool AF.

Protip: if you’re deciding to correct someone in public, don’t start with “ummm.” It’s not a good look. Especially if you’re correcting something that wasn’t actually wrong in the first place.

Anyway. The notion that Joshua trees are not trees isn’t new. I’ve run into it on and off for at least 25 years, and that’s only because I wasn’t looking earlier than that. For some reason, it’s popping up a lot more recently. Maybe it’s social media critical mass, fueled by the recent newsworthiness of the plants’ namesake national park, a proposed listing as Threatened by the state of California, and several years’ worth of peer reviewed studies showing the plants are likely to be wiped out in Joshua Tree National Park in the next century or so. At any rate, the trope is showing up more often, including use by people who really, really ought to know better.

Screen capture from Google search results

Possibly the worst version of the assertion, which Ben Maas veers toward in his Tweet above, is the version that popped up in the Orange County Register a couple years back: “Technically Joshua trees are not trees, they are plants.”

Indulge me, please, as I reply by way of Venn diagram.

Trees are plants, people. What’s wrong with you?

And Joshua trees are trees, like it says on the tin. Or, more properly, they are trees except when they are not. Some Joshua trees grow more like shrubs, and disagreements over the distinction between “shrub” and “tree” are unlikely ever to be resolved to anyone’s satisfaction, which everyone that ever argues the distinction knows full well. Trees have a tall trunk and shrubs have several short trunks, except that some trees, like clumped paper birches, are more often seen as multitrunked specimens and yet they’re too tall to be considered shrubs. Meanwhile everyone’s grandparents know someone that has a hybrid tea rose in her garden, and those are pruned to a single trunk, so are they trees? No, because they’re too short to be trees. And that dwarf Alberta spruce tree next to the rose? A little shorter than the rose, in fact? Is that a shrub or a tree?

This is the kind of discussion that makes one reach for the bottle of aspirin, which coincidentally was first synthesized from the bark of willows, which defiantly stand with a foot on either side of the shrub/tree line, and they shall not be moved.

It strikes me that part of the reason that there’s no hard and fast definition of the dividing line between tree and shrub is that there is no hard and fast definition of “tree.” Not in the sciences, anyway. And if there’s no canonical definition of “tree,” then nothing keeps the Joshua tree from being one.

I should point out that sometimes, you will see a person propose that Joshua trees are not true trees because true trees exhibit what’s called “secondary growth,” namely that expansion of the trunk by way of a vascular cambium that causes oaks and pines to show annual rings in cross section. Joshua trees are monocots, more closely related to grasses and orchids, and their trunks in cross section show the vascular bundles more typical of monocots. Hence no annual rings, no secondary growth, and no lack of people claiming falsely that this excludes Joshua trees from treedom.

Might I point out that the definition of “tree” to which these people refer is limited to just one industry? That industry is forestry, a pleasant name. The second verse of this excellent song by Leon Rosselson describes the industry pretty well. Listen to all three verses, though. Not enough people know this song.

I appreciate a fine clear-heart two-by-eight as much as the next fella, but there’s no denying that forestry, at its heart, involves killing trees, dismembering them, then selling off the good bits to whoever is interested. Using a definition of “tree” used only by the forestry trade is exactly like using a definition of “bird” promoted by Harlan Sanders. Foresters have a vested interest in defining “tree” to mean only those profitable species of tall, usually single-trunked plants. Half the time they won’t even admit alders are trees.

Besides which, there’s something truly messed up about a definition of “tree” that at its root, you should pardon the inadvertent pun, requires cutting one down.

Fortunately for us and for the Joshua trees, botanists in general have no such limits on who they will allow into the tree club. I was reminded of this the other day when expounding on this precise topic on Twitter:

Chris Clarke @canislatrans

People are always saying this, but no one has ever been able to point me to an authoritative definition of the word "tree" that would exclude Joshua trees. I am reasonably certain that this is because there is no such definition.

Base Camp Nevada @BaseCampNevada

Although technically not a tree (they’re succulents belonging to the genus Yucca), I still love #JoshuaTrees just as much as the real thing #NationalLoveATreeDay https://t.co/Z7OzJvO5Oj

(Fortunately for me, the good folks at @BaseCampNevada took my unsolicited feedback in good humor. You should follow them if you do that kind of thing.)

A handful of my botanist friends chimed in in amused and maybe a little weary sympathy. One pointed out that the California Native Plant Society’s online Manual of California Vegetation classifies the Joshua tree as a tree. (Somebody’s gotta fix that range map, with its extension of Joshua tree woodland up to Tioga Pass.)

And then came forest scientist Tom Kimmerer with the best working expert definition of “tree” I’ve ever heard.

Tom Kimmerer, PhD @tomkimmerer

@canislatrans As a tree physiologist, I have read many erudite definitions of “tree,” none of them satisfactory. I finally settled on a working method: ask a 4-year-old. If she says it’s a tree, that’s good enough for me.

Me too.

Why bother with all this? The way I see it, if you don’t complain about trivial problems, then you’ll spend the time you devote to bigger problems complaining about them rather than fixing them.

And on the topic of fixing problems, the next LFtD will cover the attempt to list Joshua trees, which I’ve already covered in some detail, except that was before powers that be where I live decided to oppose the listing. They also want to restart daily commerce now, despite an absolute lack of any progress on the pandemic around here. Same folks don’t care if either Joshua trees or you make it to the next century. That’s worth fixing. Here, have a picture of a tree.

Creative commons photo by Traveler858

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