If it seems to you like juniper are everywhere, well, they are. Western junipers are among the most common trees in Oregon — in some areas, essentially the only tree. Once thought to be all one species, recent scientific work has shown that there are actually two species of Western juniper, although the one you see in Oregon are Juniperus occidentalis.
Western junipers possess a paradoxical dual nature. They are delicate young trees, yet tough and long lived. They are fire susceptible when young, yet resistant as old specimens. About half are monoecious (containing either male or female reproductive structures), and about half are dioecious (containing both sexual structures). This dual nature of sexual reproduction can be confounding because the roughly half that manifest as either male or female, do so in a changeable ratio that can vary from year to year depending upon growing conditions. Male reproductive structures produce pollen, and female structures produce those small orbs commonly referred to as “berries,” which show great variability in abundance. Since juniper are conifers, those aren’t berries, but rather a tiny cone, housing a couple seeds, covered with a fleshy outer layer, that in turn hosts a protective yeast bloom on its surface.
Western juniper’s duality appears again in the way they offer habitat to both predators and prey. Chipmunks and golden mantled ground squirrels live in cavities in old trunks and forage in the canopy, as do the owls and hawks that hunt them. Insects attracted to juniper fruits are eaten by bats that roost in the tree’s gnarled bark. Juniper roots can house both coyote dens and rabbit burrows. Deer shelter under them, even as cougars stash their carcasses up in the branches.
Perhaps it is all this duality that earns them mixed reviews from people. Some Central Oregonians see juniper as useless trash trees; others enjoy their lumber in our homes, their “berries” flavoring our gin, or their lovely aroma as a Christmas tree or wood burning in our campfires. Beauty is in the eyes of the beholder to be sure.
Two bird species, American robin and Townsend’s solitaire, are particularly fond of those berry-shaped cones. Both of these bird species also love the insects, worms and fruits in our farms and gardens, and have helped spread juniper far and wide. Interestingly, there’s evidence that bird population swings and juniper reproductive abundance are tied together: warmer, wetter weather makes good conditions for junipers, which make more berries, which attracts more birds. Life makes more life, an expansion of resources in one area bumping up resources in another.
This now ubiquitous tree was once much less dominant in this landscape. It grew only in areas with poorer soils, or rocky ridge lines, where competition from bunch grasses and shrubs was limited, and where fire did not often reach. Bunch grasses are highly fire-adapted with dense root mats and fast growth. These bunch grasses were very successful in the historic pattern of more frequent small fires — sometimes set by Native tribes to improve hunting and foraging — and they easily out competed thirsty young juniper.
Today, juniper cover an estimated three times as much land in Oregon as they did in pre-European settlement times. How did that happen? As in so many areas of life, “it’s complicated,” but a key driver was the proliferation of open range livestock grazing — just at the same time as climactic conditions were swinging favorably for juniper. While Native inhabitants had long set small fires, European settlers tended to suppress fires. As shrub communities were altered and livestock consumed bunch grasses, their grazing simultaneously introduced and enhanced the spread of invasive grass and weed species. All of these disruptions enabled juniper to thrive and spread.
The juniper population boom presents a dilemma. Though they are native, scenic, and wonderful habitat for many wildlife species, juniper are also notoriously thirsty trees that, at the expense of declining bunch grass communities, pull tremendous amounts of water out of this arid landscape. As juniper expand beyond their historic range and density, millions of public dollars are being spent to control juniper through cutting and burning — largely short-term efforts — without adequately addressing the root causes.
The next time you walk by a Western juniper, likely today, marvel at this species adaptability and complexity, and perhaps view it as an opportunity to restore balance to the landscape.
—Scott Bowler is a retired science educator and a volunteer with Oregon Natural Desert Association, a nonprofit organization that protects and restores Oregon’s high desert public lands and waters. Read more of his work at onda.org/author/scott-bowler.
This article appears in Dec 7, 2022 – Dec 13, 2023.
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Interesting article! Hmm though, I’ve read in multiple other publications that junipers are not native to Central Oregon. Guess there isn’t consensus there.
The are native to our region. No debate in that account, just on amount pre and post settlement.
The are native to our region, have been for millennia. Debate is over pre and post settlement distribution. As usual our settlement actually increased its range through over grazing and fire suppression.
Fascinating, thank you. Especially interesting was the variability in male female reproduction relative to environment. Might explain why pollen levels and ‘berries’ are so changeable year to year.
Personally, I marvel at the juniper’s rugged appearance, the hardness of its wood, and how darned scrappy they are overall.
Water fiendishness however, is not a positive trait!
People must remember that many of us live in one of the most significant old growth juniper forests on Earth. Junipers are notoriously thirsty, but are also the only tree able to simultaneously survive months without water, and then barely any at all during our bitterly cold winters. Many of us live between those rocky ridges, often in sandy soils that locally never supported much grass or anything else at all besides spring flowers, shrubs and ancient junipers. My mom’s family came to Cline Falls in 1913 and, like all the locals then, would heat their home with old growth juniper, 10 cords a winter. That’s a lot of trees. Besides clearing juniper for fields, it was also milled into lumber. I still have 2×4’s from that period, incredibly fine-grained, dense juniper, from trees hundreds of years old. Stumps cover miles and miles of BLM land surrounding Redmond, Eagle Crest, Plainview, Powell Butte, and Alfalfa, hinting to the magnificence of this woodland before our use of it. Juniper are essential for wildlife cover, moderating summer heat, and protecting many orbs that rely on their shade and addition of organic matter. Junipers taking over productive grasslands due to lack of fire is one thing. But locally, junipers were often more prolific before Europeans than now. Junipers in irrigated areas are definitely water hogs, but they can’t be drinking water that isn’t there. Our aquifer comes from the mountains.