Why Are My Cabbage Outer Leaves Turning Yellow?

Some outer leaf yellowing on cabbage is completely normal — the oldest leaves die off progressively as the plant channels resources into the growing head. But when yellowing is more widespread, affects multiple leaves simultaneously, progresses rapidly, or comes with wilting or stunting, something is limiting the plant. The pattern and context of yellowing is the key diagnostic tool for identifying which of several possible causes is responsible.

Natural ageing of outer leaves

The oldest, largest outer leaves of any cabbage progressively yellow and die as the plant matures. This happens from the outermost leaves inward and is completely normal — the plant is recycling nutrients from ageing leaves back into the actively growing centre. These leaves can be removed and composted; the inner head will be unaffected. If only one or two outer leaves are yellowing and the plant looks otherwise vigorous, this is normal ageing, not a problem.

Nitrogen deficiency — uniform pale yellowing

When all leaves look uniformly pale yellow-green rather than deep green, and growth has slowed, nitrogen deficiency is the most likely cause. Cabbages are heavy nitrogen feeders. Apply a balanced or high-nitrogen liquid fertiliser immediately and repeat in ten days. Visible improvement should follow within a week. Prevent it next season with generous soil preparation (compost incorporated before planting) and a granular feed at transplanting.

Clubroot — yellowing with wilting

When yellowing is accompanied by afternoon wilting (the plant recovering slightly at night), stunted growth, and small or absent heading, check the roots. Clubroot-infected roots are swollen and misshapen rather than the normal branching root system. If clubroot is confirmed, see the specific clubroot page for management — nitrogen feeding will not help a plant with destroyed root function.

Black rot — yellowing from the leaf edge inward

Black rot (Xanthomonas campestris) typically causes a V-shaped yellow-brown lesion starting at the leaf edge or tip and advancing inward, often with blackened veins visible inside the lesion. Affected leaves yellow rapidly and drop. The disease spreads through the plant systemically. If this pattern is seen, remove and destroy affected plants and do not grow brassicas in that ground the following year.