Salt burn is not a disease
On the Cronulla peninsula and the exposed points around Port Hacking, onshore wind carries salt spray well inland. It lands on foliage, dries, and burns the leaf margins. The damage is worst on the windward side, which is why a tree can look half dead from the street and perfectly healthy from the back yard.
Fungicide does nothing for it. Neither does fertiliser. The leaf damage itself is cosmetic and the tree usually keeps functioning through the sheltered side of its canopy.
Wind pruning is the tree adapting
Constant wind from one direction produces asymmetric growth: shorter, denser growth into the wind and longer limbs downwind. It looks lopsided and it is structurally sensible — the tree has grown into the loads it experiences.
The problem arises when those loads change. A tree that grew up sheltered by a neighbouring canopy, and is then left standing alone after the block next door is cleared, has a crown developed for conditions that no longer exist. That is when a southerly finds it.
The southerly buster
The Shire's characteristic wind event: a hard, sudden change late on a hot day, arriving from the south after a day of northerly or still conditions. Trees are loaded from a direction they have not been loaded from all summer, often with a canopy full of water from the rain that comes with it.
Exposed frontage at Cronulla, the open points on Port Hacking, and the ridge-top estates at Menai cop it hardest. The storm season checklist covers preparation.
What to actually do about coastal exposure
Thin, do not shorten. Crown thinning lets wind pass through a canopy rather than pushing on it. Reducing height alone does not fix the sail.
Deadwood before summer. Salt-stressed trees carry more dead material in the outer canopy, and that is the material that flies.
Accept the brown side. Removing a structurally sound tree because one side is scorched is a waste of a tree and of money.
Choose replacements that cope. Coastal banksia, tuckeroo, coast rosemary, port jackson fig and the local tea trees all handle salt-laden wind. Many popular garden exotics do not, and no amount of care makes them.
Palms on the coast
Palms take salt well but the frond load gets heavier and dead fronds accumulate faster, which matters when they are over a path or a car space. Annual frond and seed head work handles it; where a cocos palm is also feeding rats, the palm removal page covers the alternative.
Getting advice
If a coastal tree looks worse each year, the question is whether the decline is salt on the foliage or something at the base — the failure risk article sets out the difference. For pruning before the season turns, call (02) 9538 7974.