Rethinking Mountain Cedar
Habitat Enhancing Land Management
“Cedar Cathedral” Photo: Mimi Cavender
Christine Middleton
“Standing inside one of those [cedar] brakes gave the feeling of being inside one of Nature’s cathedrals.” —Williedell Schawe, Wimberley’s Legacy, 1963
One question landowners ask when the HELM team pays them a visit is “What should I do about all this cedar?” We start by dispelling myths surrounding cedar. First, it is not really cedar at all. In fact, there are no native cedar trees in North America. The tree we Texans call cedar is actually Ashe Juniper, also known as Blueberry Juniper or Mountain Cedar. Or, if you are so inclined, its scientific name is Juniperus Ashei. And yes, it is native to Central Texas. No, the junipers are not killing your oaks. And no again, Ashe junipers are not water wicks and are not drying up our springs. In fact, the trees play a key role in protecting our precious groundwater by reducing evaporation during droughts and increasing infiltration—and with it, spring flow—during wetter periods.
History of Mountain Cedar (Ashe juniper)
Based on fossilized cedar pollen, Ashe juniper has grown in Central Texas for more than 10,000 years. But wasn’t most of the Hill Country dominated by grasslands? That’s another myth, easily refuted by studying writings of 18th- and 19th-century travelers to Central Texas. When their descriptions of the landscape are mapped to where the writer was at the time, it becomes clear that reports of vast lush grasslands tend to fall east of IH35 in the Blackland Prairie region. And reports from the Edwards Plateau west of IH35 generally speak of mixed cedar/live oak forests with patches of open grassland.
One interesting example comes from the writings of Frederick Law Olmsted, 19th-century journalist and father of American landscape architecture—the designer of New York’s Central Park. He visited Hays County in the mid-1800s and described the area around San Marcos:
“Beyond [San Marcos] our road approached closely the hill-range, which is made up of spurs coming down from mountains North. They are well wooded with cedar and live-oak.”
Even today, as one crosses IH 35 and heads up over the Balcones Escarpment toward Wimberley on RR12, one can observe changes in vegetation as cedar, largely absent on the east side of IH35, becomes ever more predominant.
Cedar/oak forests clearly covered the hills west of San Marcos in 1890.
Photo: DeGolyer Library, Southern Methodist University
About the same time Olmsted travelled through Texas, the harvesting began of mountain cedar to provide railroad ties, fence posts, building materials, and fuel. Cedar harvesting accelerated as railroads were built through the area. That made possible the transportation of cedar logs across large distances. Just two decades later, an 1874 article in Austin’s Daily Democratic Statesman observed:
“The cedar tie business has contributed largely to the growth and prosperity of the ‘Hill City’ in the last two years, more especially the last twelve months. A gentleman connected with the Central Railroad says that two hundred thousand cedar ties have been shipped from this city during the last two years, and when it is remembered that these ties bring from sixty to ninety cents each, the reader will readily comprehend the vastness of the revenue from this source...”
By the early 1900s many stands of Ashe juniper were being cleared for a second time. Cedar whacking became a profession, and a special axe was invented to make the job a bit less strenuous.
Click on this link to a presentation by Lisa O’Donnell, senior biologist for the City of Austin, on the Historic Ecology of the Hill Country from 1700-1900. Her presentation starts at about the 20-minute mark. This is a fascinating history of the Ashe juniper right here where we live.
Fast Forward to Today
As land was clear cut, erosion naturally set in. This was exacerbated by overgrazing as the newly cleared land was used to raise cattle, sheep, and goats. Lots of soil washed away—a big loss, considering natural processes take 100-500 years to build an inch of topsoil. When people see Ashe juniper growing on caliche soil, they often assume the Ashe juniper caused the land to degrade. Quite the opposite—the Ashe juniper is there because the land was already degraded. In fact, it’s one of the few species willing to grow in hot, dry caliche! Look closer. Notice that under the juniper’s spreading limbs there is more plant diversity than in open areas nearby. That’s because the Ashe junipers provide shade during hot Texas summers at the same time they are building soil. And those low branches enable tender seedlings to avoid being grazed to death by deer and other herbivores.
Notice the variety of young seedlings growing among dead cedar needles.
How does Ashe juniper build soil? As needles drop, they decompose to add organic matter. Any gardener knows that as organic matter increases, so does the soil’s fertility and water holding capacity. A study at the Balcones Canyonland Preserve in Austin demonstrated (in the graph here) higher soil organic content as the age of a stand of cedar increased. Other studies there have demonstrated that Ashe juniper is much better at building soil than bunch grasses like little bluestem.
Many desirable native plants occur almost exclusively in the rich, well-drained soil the cedar has created. Among these are cedar sedge, cedar sage, Texas madrone, and Lindheimer’s silktassel. Twistleaf yucca and rarer plants such as Heller’s marbleseed, prefer juniper/oak woodlands. And some of our favorite grasses, including little bluestem and sideoats gramma, have been shown to grow better in Ashe juniper soils. Ashe juniper also activates soil fungi required before other native trees such as shin oaks, red oaks, and live oaks can take hold.
And don’t forget the berries the female Ashe junipers produce in winter. That’s why, when the weather turns colder, cedar waxwings and American robins flock here. Lots of mammals, including white-tailed deer, raccoons, foxes, and rabbits, depend on the berries when other food sources are scarce. Ashe juniper is also the larval host for the juniper hairstreak butterfly. The golden-cheeked warbler, an endangered bird that breeds in central Texas Hill Country, builds its nest exclusively from cedar bark.
The cedar brakes the first settlers found did not look like the pioneering thickets we find in much of Hays County today. In her new book, Wanted! Mountain Cedars: Dead and Alive, Elizabeth McGreevy describes two kinds of Ashe juniper trees: tree cedars and bushy cedars. Tree cedars have well defined central trunks, with a bulk of the canopy supported by upper branches. Bushy cedars branch out from stubby trunks close to the ground. When they are young, they look more like bushes, thus the term. As they mature, the bushy cedars start looking more like trees with multiple trunks that sometimes fuse as they enlarge. What causes the difference is something McGreevy is still studying.
Tree cedar
Bushy cedar
Tree cedar vs. bushy cedar—a clear difference.
How long do Ashe junipers live? Some think of them as short-lived because droughts can take their toll, and it is the dead cedars we tend to notice. But actually, junipers can live hundreds of years and grow into very large trees. We don’t see many of those majestic trees in our area today due to the wide-scale cutting during the last two centuries. And size is not always a good indicator of age because growth rates vary, depending on growing conditions. Available moisture affects their size. In one case cited in McGreevy’s book, a mountain cedar with a trunk 5.1 inches in diameter was determined to be 117 years old. She also mentions “bonsai” cedars that may be old despite their diminutive size.
There are other indicators of age that can be used to differentiate mature cedars from their younger offspring. Have you ever noticed trees with white patches on their trunks? The white patches are a bark fungus, Cynospora albicedrea. The fungus disappears after the tree reaches 30-50 years old, likely due to the disappearance of moisture from sapwood. As the heartwood continues to mature, the sap is reduced. That’s when strips of bark begin to separate from the outer layer of the trunk. And, as the heartwood dries even more, the trunks and branches start to twist.
Hard to visualize some of what we’ve just said? Watching this short video of McGreevy’s discussion with Daniel Oppenheimer from Hill Country Alliance might make it a bit easier.
Implications for Land Management
Since the early 1990s there has been a tendency to cut every cedar across wide expanses of Texas, but not for profit. Rather, the motivation stemmed in part from the myths around cedar mentioned at the beginning of this article. In particular, landowners thought what they were doing was benefitting area springs. Actually, the truth is quite the opposite. Cedars hold and build healthy soils, which help rainwater infiltrate, enhancing recharge. And that’s what keeps our springs flowing!
So what should a good land steward do about the Ashe juniper on his or her property? Every piece of property is a little different. Your first step is simply understanding the cedar you have there and the benefits it is providing for both you and your property’s ecosystem. So examine various areas of your property where cedar is growing, and ask these questions:
What is the approximate age of the cedars growing in the area?
Are they predominantly tree cedars or bushy cedars?
Is the soil deep or shallow?
How steep is the area?
What direction does the slope face?
What other plants are growing there?
What wildlife depends on this patch of cedar?
Is the stand of cedar providing privacy? Sound buffering? Wind break?
There is no single strategy for managing cedar, given the multitude of factors to consider. But clear cutting acres of trees is definitely not a good idea. Chapter 23 of McGreevy’s book provides some basic strategies for getting started on managing cedar. She points out that strategies for dealing with pioneering thickets (expanding areas of new growth) are different from strategies for wooded areas (what the pioneers referred to as cedar brakes). What is a brake? The term refers to an area with tall, well established, dense stands dominated by one species, in this case tree cedars. Pioneering thickets, on the other hand, consist of younger bushy cedars. Another difference is the existence of a healthy soil layer under brakes as opposed to thin, degraded soil in thickets. It’s a bit more complicated than we’ve thought. But important.
One factor to consider in assessing a pioneering thicket is the slope of the land. McGreevy suggests that “slopes of greater than 20 percent are better maintained by wooded areas.” But how do you measure slope? Here’s one easy way. Cut a two-by-four to a length of 50 inches. Then take the board, along with a level and tape measure, to the place you want to measure. Place the board on the downslope at a representative spot, and position the level on top of it. Raise the lower end of the board until the board is horizontal. Then measure the distance from the ground to the raised end of the board. Divide that measurement by 50 and multiply by 100 to determine the percent slope. Pretty simple!
And what about the cedar brakes—the stands of single-trunk tree cedars? One of the things McGreevy talks about in her book is dog-hair regrowth, which she points out is a normal part of a wooded area’s ecosystem. What is dog-hair regrowth? Basically, it is a dense stand of small tree cedars (“stick cedars”) that are uniform in size and age. Over time these young trees will develop into a healthy mature cedar brake. So, while you might want to do a bit of thinning, they shouldn’t be eliminated. McGreevy suggests a way to start is by thinning every third stick-cedar to stimulate faster growth among the remaining ones. Then, as the canopy fills back in, thin out a few more periodically.
Stick cedars that have been thinned to stimulate growth.
Don’t forget that the Ashe juniper you cut down is a valuable resource: free material for ecological restoration. So don’t burn it. Here are just a few thoughts on how you might use it:
Larger trunks can be used to stem erosion.
Smaller branches can protect seedlings from herbivores.
Mulched material can be spread around new plantings to hold moisture.
There’s so much more to tell and not enough room in this article to do it. Instead, we’ll let Elizabeth McGreevy do it. We highly recommend her book to landowners contemplating cedar management on their property.
And, if you would like the HELM team to visit your property and help with your questions about cedar management and other aspects of your land stewardship, click here and fill out our request form.