Troubleshooting
Lawson Cypress problems — and how to fix them
Lawson Cypress (Chamaecyparis lawsoniana) is generally forgiving once you match its basics, but a few issues come up again and again. Here is what each one looks like, why it happens, and the fix.
Phytophthora lateralis root rot
The most serious threat — a water mould causing rapid, incurable decline and death. Symptoms include yellowing, branch dieback from the base upward, and dark, discoloured cambium at the root collar. No cure; prevention through soil drainage and avoiding movement of infected soil or water is critical.
Juniper scale (Carulaspis juniperi)
White, encrusting scale insects on foliage cause yellowing and dieback. Treat with horticultural oil in late winter before hatch, or systemic insecticide in spring. Improve air circulation by thinning dense plantings.
Honey fungus (Armillaria spp.)
Armillaria root rot kills roots and basal wood, evidenced by white mycelial sheets under bark and honey-coloured toadstools in autumn. No chemical cure; remove and destroy infected stumps and roots to limit spread.
Prevent lawson cypress problems before they start
Most lawson cypress issues are care-mismatch, not bad luck. Dial in the basics:
Looking for lawson cypress in general rather than its problems? Read the full lawson cypress care guide — light, water, soil and feeding.
Lawson Cypress problems — FAQ
Why is my lawson cypress phytophthora lateralis root rot?
The most serious threat — a water mould causing rapid, incurable decline and death. Symptoms include yellowing, branch dieback from the base upward, and dark, discoloured cambium at the root collar. No cure; prevention through soil drainage and avoiding movement of infected soil or water is critical.
Why is my lawson cypress juniper scale (carulaspis juniperi)?
White, encrusting scale insects on foliage cause yellowing and dieback. Treat with horticultural oil in late winter before hatch, or systemic insecticide in spring. Improve air circulation by thinning dense plantings.
Why is my lawson cypress honey fungus (armillaria spp.)?
Armillaria root rot kills roots and basal wood, evidenced by white mycelial sheets under bark and honey-coloured toadstools in autumn. No chemical cure; remove and destroy infected stumps and roots to limit spread.