The Italian Cypress (Cupressus sempervirens) is a highly recognizable landscape plant known for its striking, narrow, columnar form, evoking the classical Mediterranean garden style. When this dense, evergreen foliage begins to turn brown, it signals significant distress. Browning is not a single ailment but a symptom resulting from various environmental issues, pests, or diseases, making accurate diagnosis the first step toward recovery. Understanding the specific cause is necessary because the treatment for a moisture problem differs significantly from that for a fungal infection.
Diagnosing Environmental and Cultural Stressors
Browning that appears uniformly across the entire tree often indicates a cultural or environmental issue impacting the root system’s ability to supply water and nutrients. Italian Cypresses thrive in Mediterranean climates and are sensitive to extremes in soil moisture; both too much and too little water can cause browning. Drought stress from underwatering causes the foliage to dry out and turn brown, typically starting at the tips and progressing inward during hot, dry periods.
Conversely, overwatering or poor soil drainage can be destructive by suffocating the roots, leading to root rot, which manifests as uniform browning and wilting. These trees require well-draining soil and need the topsoil to dry out slightly between watering cycles. Other environmental factors, such as extreme temperature fluctuations, harsh winds, or intense reflected heat, can also cause browning, sometimes called winter burn or cold damage. Young, newly transplanted trees are especially susceptible to this stress before their root systems are fully established.
Identifying Insect Infestations
Insects that target Italian Cypress trees cause browning through feeding damage, often resulting in distinct, localized patterns. Spider mites are minute pests that flourish in hot, dry conditions and are a frequent culprit for browning foliage. These pests use piercing mouthparts to suck the contents out of plant cells, creating fine, bronze-colored stippling damage on the needles that eventually causes them to turn brown.
To check for mites, hold a white piece of paper under a branch and tap the foliage, looking for tiny moving specks. Another common pest is the Cypress Aphid, which feeds on the sap of new growth, often leaving behind a sticky substance called honeydew. This honeydew promotes the growth of sooty mold, a black fungus that covers the foliage and blocks light, further stressing the tree. Wood-boring insects are less common but more destructive, leaving small entry or exit holes and sawdust, often targeting trees already weakened by other stressors.
Recognizing Pathogenic Diseases
Browning caused by fungal and bacterial pathogens tends to be non-uniform, often appearing as localized dieback on specific branches, a phenomenon known as “flagging.” Cypress Canker, caused by fungi such as Seiridium cardinale or Botryosphaeria species, is a serious disease that interferes with the tree’s vascular system. The fungus enters through wounds, such as pruning cuts or insect damage, and forms sunken, discolored lesions, or cankers, on the branches or trunk.
Cankers often exude reddish or dark resin or sap as the tree attempts to wall off the infection. The foliage beyond the canker point turns yellow and rapidly browns because the flow of water and nutrients has been cut off. Root rot, while often triggered by cultural issues like poor drainage, is a disease caused by soil-borne pathogens like Phytophthora. This disease results in the decay of the root system, causing the entire tree to decline and brown from the top down as the roots fail to function.
Treatment and Recovery Strategies
The first step in recovery is recognizing that foliage that has already turned fully brown and dry will not revert to green and must be pruned out to improve the tree’s appearance and health. For cultural problems, adjust irrigation to ensure deep, infrequent watering, allowing the soil to dry between applications. Improving soil drainage, either by amending the soil with organic matter or redirecting runoff, is necessary to prevent future root rot.
For spider mite infestations, a forceful jet of water can dislodge small populations. A dormant season application of horticultural oil or insecticidal soap is effective for heavier infestations of mites or aphids. When dealing with fungal diseases like Cypress Canker, infected branches must be pruned several inches below the visible canker. Pruning tools should be sterilized with a bleach solution between cuts to prevent spreading the spores. If the canker is on the main trunk or if the tree shows advanced symptoms of decline, consulting a certified arborist is advisable.