The Eastern Red Cedar (Juniperus virginiana) is a hardy, adaptable conifer with the most widespread range of any native North American juniper. While technically native, its modern behavior in grasslands and prairies mimics a highly aggressive, non-native plant. The question of whether it is an invasive species is complex, but the term “invasive native” is often used to describe this species. It rapidly colonizes and dominates certain ecosystems outside of its historical density, causing severe ecological and economic impacts.
The Native Status vs. Aggressive Spread
Eastern Red Cedar’s historical presence was largely confined to sites where natural fires rarely reached, such as rocky bluffs, deep ravines, or sheltered canyons. The species is highly intolerant of fire, meaning even a low-intensity grass fire can kill young trees up to four feet tall. This natural fire ecology, which historically swept across the Great Plains and midwestern grasslands, served as the primary control mechanism for the cedar population.
The aggressive expansion began with the large-scale settlement of North America and the interruption of natural processes. Fire suppression policies, put in place to protect human settlements and agricultural land, effectively removed the cedar’s main check on its population. Additionally, the decrease in traditional grazing practices, which helped reduce fine fuel loads for fires, further allowed the trees to establish themselves in open ecosystems.
The Eastern Red Cedar is a pioneer species, quick to colonize disturbed or abandoned agricultural fields, fence lines, and pastures. Its seeds, contained within a fleshy, berry-like cone, are consumed and dispersed by birds, allowing widespread distribution. This combination of effective seed dispersal and the absence of fire has allowed the cedar to rapidly convert millions of acres of open grassland into dense cedar woodlands, a process sometimes called the “Green Glacier.” In Oklahoma alone, the area covered by the species has expanded from 1.5 million acres in 1950 to an estimated 6 million acres by 1996.
Ecological Consequences of Proliferation
The unchecked proliferation of Eastern Red Cedar results in a profound ecological shift, particularly in former grassland and prairie ecosystems. As dense stands of cedar develop, they shade out native grasses and forbs, leading to the displacement of the diverse plant communities that define these habitats. This conversion from open ecosystems to monoculture woodlands severely limits the habitat available for specialized wildlife, such as ground-nesting birds, which rely on the open structure of the prairies for survival.
The trees also significantly impact the regional water cycle through a process known as canopy interception and high transpiration rates. The evergreen foliage of the cedar intercepts rainfall, which then evaporates before reaching the ground, leading to increased precipitation loss. Studies suggest that dense cedar stands can intercept between 25% and 60% of bulk rainfall, preventing it from reaching the soil.
Furthermore, mature cedars are highly efficient water users, with some large trees consuming as much as 13 to 16 gallons of water per day. This high water consumption year-round depletes soil moisture, reducing surface runoff and the potential for deep groundwater recharge, which can lower streamflow in nearby watersheds. Model simulations suggest that a complete conversion of rangeland to cedar woodland could reduce streamflow by 20% to 40% in some Great Plains watersheds, depending on the climate’s aridity.
Controlling Unwanted Growth
Managing Eastern Red Cedar involves a combination of targeted approaches, and the non-sprouting nature of the species simplifies control measures. A primary and highly effective method for small trees is prescribed burning, which reintroduces the natural control mechanism the ecosystem has historically relied upon. Controlled fires effectively kill cedars less than three to four feet tall, making a burn cycle of every three to four years an effective maintenance strategy for grasslands.
For larger, established trees, mechanical removal is typically the most economical and effective option. Since the tree will not re-sprout, cutting the trunk off at or near ground level, below the lowest green branch, kills the tree outright. Heavy machinery like dozers or skid loaders equipped with shears are used for widespread removal of trees over ten feet tall, though hand tools are suitable for smaller efforts.
Chemical control offers a third option, often used in conjunction with mechanical removal or in areas where fire is impractical. Herbicides containing active ingredients like picloram are effective for treating the soil at the base of the plant or for targeted foliar application on smaller trees. For large trees that have been cut, a herbicide like triclopyr can be applied directly to the cut stump to prevent any chance of re-sprouting and ensure complete eradication.