Why Are the Edges of My Cabbage Leaves Turning Brown?

Brown, papery, dried margins on cabbage leaves — the edges and tips turning tan or dark brown while the central leaf tissue remains green — is marginal leaf scorch. In cabbages, this most commonly results from drought stress, fertiliser salt burn, or wind desiccation on exposed sites. It is not a disease and it is not infectious. The outer leaves are most affected; the growing centre and forming head are usually unaffected. Understanding the specific cause determines whether anything needs to be done immediately.

Drought-related scorch

In dry summer conditions — particularly on free-draining or very light soils — the leaf margins are the furthest point from the main water supply through the stem and are the first to show signs of moisture stress. Brown margins that worsen during dry spells and improve (or stop progressing) after rain or irrigation are drought-related. Water the soil thoroughly around plants during dry spells; mulching around plants retains moisture and reduces the severity of marginal scorch during dry periods. This is the most common cause of marginal scorch in summer.

Fertiliser salt burn

Excessive fertiliser application — particularly granular fertiliser applied in large amounts close to the plant stems and not watered in — can cause salt burn at the leaf margins. The high salt concentration around the roots draws water out of root cells rather than allowing uptake, causing the outer leaves to scorch. This typically appears relatively suddenly after a feed in dry conditions. Water thoroughly around all plants after any fertiliser application to dilute the salt concentration. The damage already done will not reverse, but further application should be avoided until the soil has been flushed.

Wind desiccation

On exposed, windy sites, drying wind accelerates water loss from leaf margins faster than the plant can replace it, causing physical desiccation and browning at the most exposed points. This is most notable on large outer leaves in windy spring weather before the plant is fully established. Windbreaks, staggered planting, and choosing a more sheltered position for the brassica bed reduces this. The leaves already damaged will not recover, but established plants with larger root systems cope better in subsequent windy periods.