Cypress trees are turning brown – here’s why

Cypress trees turn brown when their water balance, biology, and location are not in harmony; each of the following causes has its own specific damage pattern.

• Drought stress and heat: Prolonged dry spells draw water from the scale leaves, causing the needles to turn dull green and then rust brown. Drive a screwdriver 10 cm deep into the soil – if hardly any soil sticks to it, water immediately. A drip hose with a capacity of 2.2 liters supplies 18 liters per plant location per week in a 1.8-meter-high hedge. Cover the root area with 7 cm of wood chips; the layer reduces evaporation and keeps the soil active.
• Phytophthora root rot: Permanently wet soil blocks oxygen, allowing Phytophthora to enter through the fine root tips. Typical symptoms include yellowish crown areas at the bottom, sparse growth, and black-brown vascular bundles. Check the drainage: a 30 × 30 cm hole filled with water must drain in ≤ 30 minutes. If water remains, lay a 40 cm deep gravel channel with a 5% slope and mix sand into the top layer of soil.
• Kabatina shoot dieback: Kabatina thujae attacks young tips after wet weather. Sharply defined brown shoot sections and tiny black fruiting bodies on the bark reveal the fungus. Cut back affected areas 20 cm into healthy wood, burn the cuttings, and immediately spray potassium phosphonate as a tonic on the remaining crown to stimulate the tree’s own defenses.
• Seiridium bark canker (Cypress canker): Seiridium cardinale penetrates through cuts, forming resin-moist, oval bark lesions and interrupting the sap flow there. Remove entire branches down to the base of the trunk, disinfect every tool with 70% ethanol after cutting, and avoid rough hedge trimming during rainy periods.
• Cypress aphid (Cinara cupressi) and bark beetles: The aphid sucks in early summer, later leaving gray molting remains and sooty coatings; brown spots usually start 1.5 m above the ground. Bark beetles leave boring dust at the base of the trunk. Use predatory bugs or rapeseed oil preparations against aphids and attract woodpeckers and parasitic wasps by creating deadwood habitats to reduce beetles in advance.
• Planting errors (too deep, compacted soil, too close together): A planting hole 1.5 times the width of the root ball ensures air pockets, and the edge of the root ball should be level with the surrounding soil surface. Allow 30 to 35 cm spacing in hedges; closely planted rows develop a lack of light in the center, causing needles to fall off on their own. Loosen compacted areas with a digging fork in a star shape without tearing off roots.

Sustainable care and prevention