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A Second Look at Rocky Mountain Junipers

 

Rocky Mountain Junipers in Colorado Springs


A Second Look at Rocky Mountain Junipers
by Bryan Fischer, Horticulturist, Gardens on Spring Creek

Easily overlooked, the Rocky Mountain juniper (Juniperus scopulorum) has almost become what vanilla is to ice cream – classic and effective, yet so widely used few of us ever take note of its presence. The compelling, enhanced natural juniper trees in the “Mountain Wildwoods” exhibit give us pause to reconsider this notion.

What if, just because we can grow a species of plant almost anywhere doesn’t mean that we should?  Would that help us better appreciate the juniper for its natural merits, rather than the disheveled, over-sheared green blob we see in parking lots everywhere?

Often, the more unusual a plant is in our landscapes, the more noteworthy it becomes. This is especially true if we do the Rocky Mountain juniper the service of picturing where one might naturally find it in the wild – on lean, gritty soils, with limited precipitation or irrigation and in an environment with extreme temperature fluctuations that forces such plants to grow conservatively. 

Rocky Mountain Junipers in the Ojito Wilderness Are of New Mexico

Though they thrive in a variety of moisture regimes and environments, it is believed that historically, wildfire would have restricted Rocky Mountain juniper to harsh microclimates typified by rock outcroppings, grit-dominated soils and sparser grass and forb cover between trees. Even the scientific name of this tree reflects these origins, as scopulorum is a Latin word referring to the plant being “of rocks / rocky places”.  Thin bark (especially on young juniper trees) predisposes these trees to death by wildfire, excluding them from dominating environments that burn regularly, like prairies. Without such burns, junipers can encroach upon neighboring grassland and sagebrush-dominated environments, altering plant communities and species composition of plants and animals alike. 

As a result, many of the most mature junipers in the American West occur in incredibly harsh environments, like on rock outcroppings, cliffs and on what many gardeners would consider “bad soils”, where less understory growth doesn’t permit intense or regular wildfires. To help survive such harsh environments, junipers have reduced their needles to flat scales which have less surface area and produce a thick, waxy coating to further reduce water loss. Such trees also grow conservatively, with limited soil moisture available throughout the year.  This slow, dry growth concentrates resins and other rot-resisting phytochemicals, producing tighter tree rings – and denser wood – which even further limits likelihood of rot.

The exceptionally slow growth of our Rocky Mountain juniper means that junipers of even modest size can be of enormous age: according to the U.S. Forest Service, J. scopulorum individuals don’t even peak in seed production until they are 50 – 200 years old!  Think about what that might imply for the age of the last fruiting juniper you may have hiked past. At 300 years old, J. scopulorum trunks only measure an average of 17 inches in diameter measured one foot off the ground.

Rocky Mountain Juniper berries

Though often referred to as berries, the blue-gray fruits on these trees are actually modified cones designed to be ingested by birds and other animals. A thick seed coat helps to protect juniper embryos as they pass through the digestive tract of such animals, during which time they can easily be carried miles to be distributed in a new locale.  This effective seed dispersal strategy, as well as the incredible adaptability of juniper trees, could be why J. scopulorum plants can be found in an array of latitudes. Spanning elevations from near sea level to over 9,000 feet, these trees can be found from the Mexican to Canadian border across the Western United States.

So, perhaps, these spectacular individuals serve to remind us of a few important lessons, both in regional horticulture and more broadly – too rich a lifestyle may leave one burned, while taking a slow and steady approach can be to one’s advantage.  And, to be undaunted doesn’t mean to be without a few scars, twists and snarls.  But don’t worry; they look good on you.

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