Why is my peach tree bark splitting and cracking?

Cracked or split bark on a peach or nectarine tree is alarming to find, but the cause and prognosis depend heavily on where the splits are located, what season they appeared, and whether there is any oozing or dead tissue underneath. Some splits are harmless; others signal serious disease.

Frost cracks in winter

The most common reason for bark splitting on peach trunks is winter frost. During cold nights the outer bark contracts faster than the wood beneath it, creating vertical cracks — often called frost cracks or frost shake — along the south or southwest-facing side of the trunk. These cracks typically run a few centimetres deep and may be several inches long. The tree will usually callus over them in spring, but paint the wound with grafting wax or wound sealant to keep pathogens out. Wrapping the trunk with hessian or fleece in late autumn reduces the risk for young trees.

Rapid growth in spring

After a slow winter or following heavy pruning, a peach tree can produce very fast spring growth that causes the inner bark to expand more quickly than the outer bark can accommodate. The resulting splits are horizontal or diagonal, usually on young branches, and have clean green tissue underneath. These almost always heal on their own. Do not seal them — allow air to dry the exposed wood and the callus will form naturally.

Bacterial canker as a cause

If the split bark is accompanied by a gummy amber exudate and the wood beneath is reddish-brown and dead, the cause is almost certainly bacterial canker caused by Pseudomonas syringae. Canker splits tend to be sunken, darker than the surrounding bark, and expand over successive seasons. The affected bark needs to be cut away to healthy wood in late summer using sterilised tools, and the wound treated with a copper-based bactericide. Prune in late summer to reduce the risk of the pathogen entering through fresh cuts in wet conditions.

Sunscald on the south-facing trunk

On warm winter days the sun heats the south-facing trunk, causing the bark to warm up and begin metabolic activity. When temperatures plummet after sunset, the bark is damaged by the sudden freeze — a phenomenon called sunscald or southwest disease. The bark may later peel, crack, and die in strips. Wrap the trunk with reflective trunk guards or whitewash it with diluted white latex paint in late autumn to reflect winter sun and moderate temperature swings.

What to do with an open split

For any split without signs of disease beneath, clean away loose bark with a sterilised knife, shaping the wound into a smooth ellipse to encourage callus formation. Apply wound sealant if the exposed area is larger than your palm. Monitor monthly and remove any fresh dead wood around the edges as the callus progresses. A well-fed tree with good drainage will close moderate splits within one to two growing seasons.