The Tree of Knowledge

Munz oak leaf

In the highlands of Joshua Tree National Park my friend Seth leads me to a mature oak. "It's not like the scrub oaks in the hills around here," He says. "It's a live oak, tree-sized, and it's different from everything else around it." We round a curve and there it is: a mature tree with a trunk a few feet thick and a messy crown. Its leaves are an odd light green with almost a blue tinge to them. I don't know what kind of oak it is, and I don't realize as I take a dead leaf for later identification that I'm about to connect one of humankind's oldest technologies with one of our newest.

The tree's leaves are unlike any I've seen on a desert oak: broad and scalloped, more like the deciduous valley oak of Central California than any scrub oak I know. Not that I'm an expert. My knowledge of oaks is pretty much limited to the species I encountered in the Bay Area where I spent most of my adult life so far; three species of live oak and a couple deciduous ones, including the above-mentioned Valley oak, Quercus lobata. And distinguishing among the oaks I know can be tricky. They all have their own distinct characteristics. The three live oaks in the Bay Area, the coast, interior and canyon live oaks, are variable in leaf shape, and they hybridize readily with each other and with local shrubby oak species.

This tree looks so much like a valley oak that it's spooky. It can't be one, though. The leaves have teeth. Where valley oak's sinuous leaf margins are as smooth as any oak I know, these have little spines at the tips of each lobe. Also, they're still on the tree in December: valley oaks are deciduous. They drop their leaves in the fall. Lastly, valley oaks don't grow in the desert. They need groundwater. This is a spring, and the soil is likely to be wetter here than elsewhere in the surrounding Mojave, but even if there's enough water here most of the year to support a valley oak, there's the little question of, well, the surrounding Mojave. Where would the tree's parents have come from?

It couldn't be a Quercus lobata, but I started wondering about something anyway. Native Californians in oak country lived on acorns the way modern Americans live on refined wheat and high fructose corn syrup: acorns made up the majority of a person's diet, at least in some parts of the year. I looked at a large boulder near the tree, and sure enough it was there: an indentation in the rock at the boulder's top where women grinding acorns with a stone hand pestle had worn the hollow smooth over time.

There was a deeper, older mortar hole on the side of the boulder. A story lasting generations played itself out in my mind. The boulder had cleaved from the large outcrop a few yards away, and generations of women used it as a grinding rock, drilling a hole six inches deep in its top. Then an earthquake came and toppled the boulder, or a flash flood undercut the soil beneath it to one side, and the grinding hollow now pointed uselessly horizontal. The women started a new work surface on the boulder's new top.

Story continues below

Valley oaks didn't have a reputation for tasty acorns, and their moist flesh required a lot more drying for storage than other species' acorns, but perhaps this tree offered a break in the routine, seeing as it must have been the only one of its kind for miles. I wondered whether the acorns from this unique tree might have been coveted in the area, or envied, a family's claim to fame.

Who knows? But it's pretty certain that the knowledge of the tree had been handed down for some time, centuries at least. The tree is large, and the abandoned grinding holes deep. How many generations of mothers put that smooth, heavy pestle in their daughters' hands, taught them how to work for hours without tiring too quickly? How many generations of grandmothers leavened the tedious labor with stories, songs, and cutting jokes about the local men?

It was a technology, knowledge and artifact, that kept a people alive.

I brought the leaf home and pulled out the Jepson Desert Manual. An authoritative reference to plants of the California desert, it was no particular help. Neither was the larger Jepson Manual for the entire state. I tossed the leaf on my scanner and uploaded an image to Facebook, intending a puzzle for my botanically inclined friends. In just over an hour one of those friends -- a research associate at a botanic garden -- told me not only what the tree was, but exactly where it was.

The oak tree to which Seth introduced me was a Munz oak, Quercus X munzii, the X being the mark in botanical nomenclature of a known hybrid between two species. In the case of the Munz oak, the two parent species are Quercus cornelius-mulleri, a common desert shrub-oak, and the valley oak, Quercus lobata.

The hybrid's recorded from three places in the state. One was collected northwest of Arroyo Seco in Monterey County in 1963. Another was noted east of Anza in 1947 by Philip A. Munz, the elder botanist for whom the hybrid was later named. And one is here, in Joshua Tree National Park, in a few spots between the Pinto Wye and the Wonderland of Rocks.

I had, in fact, snagged a leaf from the very tree that UC Davis botanist John Maurice Tucker had used to name the hybrid species.

I felt a little bit of psychological whiplash. I'd spent half an hour on our hike that day thinking about the deep botanical knowledge passed along by women using stone tools and woven baskets, and suddenly I was learning similar stories about the tree with technology I couldn't have imagined when I was a child. Silicon in the granite pestle and silicon in the semiconductors, each of them in their own way helped to pass along stories. It's just that now we've taught the stones to talk on their own.

Chris Clarke is an environmental writer of two decades standing. Director of Desert Biodiversity, he writes from Joshua Tree regularly at his acclaimed blog Coyote Crossing and comments on desert issues on KCET weekly. Read his recent posts here.

For ongoing environmental coverage in March 2017 and afterward, please visit our show Earth Focus, or browse Redefine for historic material.
KCET's award-winning environment news project Redefine ran from July 2012 through February 2017.

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