Arborvitae are popular evergreens, often chosen for their dense foliage and ability to create natural screens. Like any plant, arborvitae can decline due to various factors. Recognizing early signs of distress allows for timely intervention, which can often reverse decline. This guide identifies common symptoms and their underlying causes, offering a path to restoring your arborvitae’s health.
Key Signs Your Arborvitae Is Struggling
Observing your arborvitae for visual cues is the first step in diagnosing a problem. Changes in foliage color and texture often signal underlying issues.
Browning or Yellowing Foliage
Foliage discoloration is a common symptom. Browning can appear at branch tips, indicating issues like winter burn or drought stress. Uniform yellowing often suggests overwatering or nutrient imbalances. Browning may also progress from the inside outwards, where older, interior needles turn brown and drop; this is natural but can be exacerbated by stress.
Needle Drop and Bare Branches
Excessive needle drop, particularly from the inner parts, indicates decline. While some interior needle shedding is normal, an unusual amount suggests a problem. Bare patches or branches within the dense canopy point to significant stress or damage. These areas may reveal brittle or dead twigs lacking green growth.
Weak Growth and Structural Issues
A general lack of vigor, characterized by stunted new growth or sparse foliage, indicates a struggling plant. Branches may become brittle and snap easily, rather than bending, a sign of dead wood. In severe cases, the plant might appear leaning or show instability, pointing to root problems or structural damage.
Presence of Pests or Diseases
Signs of insect activity, such as fine webbing, small holes, or sticky residue, indicate a pest infestation. You might also notice abnormal growths like cankers (sunken lesions) on stems or branches, or fungal structures such as mold or spore masses.
Understanding the Causes of Decline
After identifying signs of distress, pinpointing the specific cause is the next step toward effective treatment. Various environmental factors, pests, and diseases can contribute to an arborvitae’s decline.
Environmental Stress Factors
Water extremes are common causes of arborvitae decline; both insufficient and excessive moisture cause stress. Drought stress leads to browning foliage, especially during hot, dry periods. Conversely, overwatering or poorly draining soil can lead to root issues as roots become waterlogged, preventing oxygen uptake.
Winter desiccation, or winter burn, occurs when cold winds and frozen ground prevent the plant from replenishing moisture lost through its needles, resulting in browning, particularly on exposed sides. Salt damage from road de-icers can also cause foliage burn. Transplant shock, experienced by newly planted arborvitae, occurs when the plant struggles to establish its root system.
Pest Infestations
Several pests target arborvitae. Spider mites are tiny arachnids that feed on plant cells, leading to a stippled or dull appearance of the foliage, which may eventually turn gray or brown. They often create fine webbing. Arborvitae leafminers are larvae of small moths that tunnel inside needles, causing them to yellow and then brown from the tip downward. Bagworms are caterpillars that construct distinctive silken bags covered with bits of needles; their feeding can defoliate branches or entire plants.
Common Arborvitae Diseases
Arborvitae are susceptible to certain diseases, many fungal. Root rot results from consistently wet or poorly draining soil, where fungal pathogens attack roots, leading to plant decline and yellowing or wilting foliage. Tip blight, caused by fungi like Pestalotiopsis or Phyllosticta, results in browning and dieback of needle tips, often progressing inward. This disease frequently affects weakened plants. Canker diseases, such as Phomopsis or Seiridium canker, cause sunken lesions on branches and stems, restricting water and nutrient flow, leading to branch dieback.
Other Contributing Factors
Other factors can impact an arborvitae’s health. Animal damage, particularly from deer, can lead to defoliation. Voles or other rodents might gnaw on the bark at the plant’s base, girdling the stem and disrupting nutrient transport.
Nutrient deficiencies can manifest as discolored or stunted growth. Improper planting depth can suffocate roots and inhibit establishment. Older arborvitae may naturally decline, showing reduced vigor and increased susceptibility to problems.
What to Do When Your Arborvitae Shows Signs of Decline
Addressing arborvitae decline requires a thorough assessment of the plant and its environment. Early intervention can often improve the plant’s health, but some situations may require professional assistance.
Initial Assessment
Begin by closely examining your arborvitae and its surrounding area. Check soil moisture by inserting a finger or moisture meter a few inches deep to determine if over or under-watering is occurring. Inspect foliage and branches for pests, webbing, or unusual growths like cankers or fungal spots. Also, look for signs of animal activity, such as chewed bark or disturbed soil around the base.
Basic Remedies
Adjusting watering practices is a primary step, ensuring the soil remains consistently moist but not waterlogged. For newly planted arborvitae, consistent watering for the first two years aids establishment. Lightly prune any dead or severely damaged branches, cutting back to healthy green wood. Providing temporary shade during intense summer heat can reduce environmental stress. Improving air circulation by removing weeds or crowded plants nearby can also be beneficial, especially in humid conditions.
When to Seek Professional Help
Consult a certified arborist or landscape professional if damage is widespread, affecting a large portion of the plant or multiple arborvitae. Seek professional help if you cannot identify the cause of decline or if the plant’s condition worsens despite your efforts. Large or valuable arborvitae often warrant professional diagnosis and treatment. An arborist can provide a definitive diagnosis and recommend targeted treatments.
When It’s Too Late
Some arborvitae may be beyond saving, especially if decline is extensive or long-standing. Signs a plant is too far gone include brittle, dead branches that snap easily without moisture or green tissue underneath the bark. If the trunk shows severe rot or extensive cankers, or if the plant has declined for several years, removal might be the best option. Focus on maintaining the health of remaining plants or selecting new, healthy specimens for replanting under optimal conditions.