The term “cedar tree” often refers to coniferous species beyond the true cedars (Cedrus), which are native to the Mediterranean and Himalayas. Many common landscape trees, such as Juniperus (junipers) and Thuja (arborvitae), are colloquially called cedars and are frequently the source of homeowner and environmental complaints. While the aromatic wood and stately appearance of these conifers are valued, their presence can introduce significant problems. The following issues—ranging from direct impacts on human health to complex ecological shifts—explain why these trees are often viewed as problematic.
Health Risks Associated with Cedar
One widely reported health issue is the intense seasonal allergy known as “Cedar Fever,” caused by the abundant pollen of the Ashe juniper (Juniperus ashei), commonly called mountain cedar, not true cedars. This tree releases massive, visible clouds of pollen during the winter months, typically December through February, in areas like Central Texas and Oklahoma. The timing often leads to symptoms being mistaken for a cold or the flu, including intense nasal congestion, severe sneezing, fatigue, and sometimes a low-grade fever.
The microscopic pollen grains are highly allergenic and can travel for miles on the wind, making avoidance nearly impossible for sensitive individuals. The sheer density of the pollen released by these male juniper trees can overwhelm the immune system, triggering an exaggerated response where mast cells release histamines into the bloodstream. For people with pre-existing respiratory conditions like asthma, the intense exposure can lead to worsened symptoms, including wheezing and chest tightness.
Cedar products also pose a direct toxicity risk to small animals due to their volatile organic compounds. Shavings and bedding made from aromatic softwoods, particularly cedar, release high concentrations of phenols, which are the source of the wood’s characteristic scent. These phenolic compounds are toxic to the respiratory and hepatic systems of small mammals, such as rodents and poultry, when inhaled over time.
Continuous exposure to these aromatic hydrocarbons in bedding causes respiratory irritation and can significantly elevate liver enzymes in laboratory animals. This increased enzyme activity indicates the liver is working harder to detoxify the absorbed compounds, which can alter drug metabolism and stress the animal’s internal systems. Many pet advocates advise against using cedar bedding, as it can lead to chronic illness and reduced quality of life for sensitive species.
Landscape and Maintenance Challenges
The aesthetic appeal of many cedar and juniper species in a landscape setting is often offset by numerous maintenance and structural difficulties. Many popular varieties, including Eastern red cedar (Juniperus virginiana), are inherently shallow-rooted, especially when grown in compacted or clay-heavy soils. This growth habit makes the trees susceptible to falling in high winds, and the roots can become a nuisance in manicured areas.
As these shallow roots expand, they often grow close to the soil surface, creating tripping hazards and interfering with lawn maintenance. More seriously, the lateral root expansion can lift and crack nearby sidewalks, driveways, and patios, leading to costly infrastructure repairs. Although the roots rarely cause structural foundation damage, they can exploit existing cracks in pipes or foundations to seek water, causing blockages or exacerbating soil movement.
A major horticultural concern is the role of juniper species as the alternate host for fungal diseases, notably Cedar-Apple Rust (CAR), caused by Gymnosporangium juniperi-virginianae. This fungus requires two different plant hosts to complete its life cycle: a juniper and a member of the rose family, such as apple or crabapple trees. On the juniper, the fungus forms woody galls that swell and produce orange, gelatinous spore horns in the spring.
These spores are carried by the wind to susceptible apple and crabapple foliage, causing bright yellow to orange spots on the leaves and fruit, which can lead to premature defoliation and crop loss. While the rust rarely kills the juniper host, its presence within a two-mile radius can compromise the health and productivity of nearby fruit trees.
Ecological Drawbacks
In many regions, the rapid spread of certain juniper species presents a complex ecological problem that alters entire landscapes. This process, termed “woody plant encroachment,” sees junipers colonize open grasslands and rangelands, displacing native grasses and shrubs. The resulting dense stands of juniper can form monocultures, which significantly reduce the overall biodiversity of the ecosystem.
This change in vegetation structure creates a feedback loop that increases the amount of bare ground between the trees, leading to greater water runoff and increased soil erosion. The establishment of these conifer woodlands also changes the fire regime, as the trees’ dense foliage and volatile oils allow fires to become more intense and destructive than the natural, low-intensity grass fires that historically maintained the open landscape.
Beyond competition for space, the water usage of large cedar and juniper stands creates significant strain on local water resources, especially in arid and semi-arid climates. Juniper species develop deep, extensive root systems that allow them to access water far below the reach of shallow-rooted grasses and forbs. This competitive advantage enables them to consume large amounts of water, depleting soil moisture available to other plants.
Studies on mature Western Juniper (Juniperus occidentalis) show that a single tree can consume a substantial volume of water daily, with transpiration rates reaching 144 liters in wet conditions. The widespread encroachment of these trees can impact the regional water balance, leading to reduced streamflow, decreased groundwater recharge, and the drying up of springs. This high water consumption makes their management a regional concern for water conservation and rangeland health.