12 Days of Conifer Bonus: Spiky Leaves Aren't Just For Conifers

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Nothing like a baker’s dozen, right? As a bonus for 12 Days Of Conifers we have…. hey! That’s not a conifer!

WERC Joshua trees

Joshua trees in desert landscape (USGS. Public domain.)

Sneaking in for a bonus day is a species that may appear to be a strange sort of conifer from a distance due to its spiky leaves, but the Joshua tree isn’t a conifer. Or even really a tree, for that matter. It’s a giant yucca, a flowering plant in the Agave subfamily. They are more closely related to an asparagus than to any conifer.

But it’s not a total coincidence that Joshua trees look a bit like conifers. Narrow, thick, or spiky leaves are an adaptation to prevent water loss in dry environments (though plants with this type of leaves can be found in wetter climates as well). The Mojave desert is pretty different from the slopes of the Sierra Nevada, but both Joshua trees and montane conifers like ponderosa pine must contend with harsh conditions.

And like many conifers we’ve seen, the Joshua tree’s hardiness has its limits: it is vulnerable to the hotter temperatures, severe droughts, and wildfires that come with climate change.

USGS’s Todd Esque has been studying Joshua trees and their ability to cope with climate change. He is a collaborator on the Joshua Tree Genome Project, a multistate effort to sequence the tree’s genome and assess how the tree’s genes may help it adapt to a changing climate.

Check out the Joshua Tree Genome Project here.

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Photo of landscape after desert wildfire

One year after a desert wildfire, the Joshua trees are left as skeletons, but globemallow (Sphaeralcea ambigua) and desert marigold (Baileya multiradiata) along with many annual food plants of the desert tortoise may be abundant. Among the bright flowers are green and red patches of the invasive red brome grass (Bromus madritensis rubens) – which fuel fires and USGS research shows is detrimental to growing juvenile tortoises.

(Credit: Todd C. Esque, USGS WERC. Public domain.)