Laurel Or Conifer Hedge Turning Brown Or Dying

What's happening?

Laurel and conifer hedges brown for different reasons. The RHS says cherry laurel leaves can be affected by powdery mildew, leaf spot fungi and bacterial shot-hole, which leave brown spots and irregular holes. For conifers, the RHS says brown patches can be caused by insects or diseases, but others come from growing conditions or routine operations such as trimming. Cypress aphid is a relatively common cause, found associated with half of the cases in an RHS research project. Pestalotiopsis fungus is occasionally associated with brown patches. If the browning affects most or all of the foliage of an individual tree, a root disease such as honey fungus or Phytophthora root rot could be responsible. With the exception of yew, conifers have little or no capacity to regrow from old wood.

What usually causes it?

• Cherry laurel leaf diseases: powdery mildew, leaf spot fungi and bacterial shot-hole
• Cypress aphid on leylandii and other conifers, where the browning often develops after the aphids have left
• Over-enthusiastic trimming into old wood, which leaves bare or brown patches that do not regrow
• Drought, frost, waterlogging or cold, drying winds, which the RHS says can inhibit regrowth from trimmed foliage
• Pestalotiopsis fungus, more likely in wet summers on weakened plants
• A root disease such as honey fungus or Phytophthora root rot, when most of one tree browns or dies

Is it dangerous?

No. It is a plant health problem. A conifer that dies completely may mean a root disease, which the RHS says to check for before replanting.

Can I fix it myself?

Look at the pattern. On laurel, check for white powder, brown spots and holes in the leaves. On conifers, look for sooty black growth and cast aphid skins, check where the patches are and whether you trimmed into old wood or at the wrong time: the RHS says die-back appeared slightly more common after autumn trimming. If the browning covers most of one tree, check for waterlogging, establishment failure or root disease. Water hedges in dry spells. If the cause is unclear, the RHS notes that laboratory examination of shoot samples may be needed.

When should you call a gardener?

Call a gardener or arborist to identify the cause, trim correctly, treat aphid problems and remove dead sections or trees. If whole trees are dying across a hedge, ask for a root disease check before replanting.

What will the gardener actually do?

• Identify the cause from the pattern: leaf disease, aphid, trimming, conditions or root disease
• Trim at the right time: the RHS says to avoid trimming in hot or dry weather or in autumn, and never to cut into old wood
• Advise on watering, drainage and mulching
• Remove dead trees and plants, and test for root disease before replanting
• Take samples for laboratory diagnosis where needed

Who fixes this

• Hedge trimming
• Garden pruning

Questions people ask

Sources & References

1. RHS: laurel leaf diseases
2. RHS: conifers with brown patches