Why Are My Cauliflower Curds Turning Yellow or Brown?

A cauliflower curd that was white when you last checked, but has turned yellow, cream or brown, has been affected by one of several common problems. The colour of the discolouration and when it appears tells you exactly what went wrong. Yellow usually means light exposure; brown more often means frost, watering stress, or the start of disease.

Yellowing from light exposure

White cauliflower curds turn yellow when exposed to direct sunlight. Chlorophyll begins to develop in the curd tissue, turning it progressively yellow then green. The traditional solution is blanching — bending the plant's own outer leaves over the curd and securing them to create shade. Do this as soon as the curd is the size of an egg. In modern self-blanching varieties the inner leaves curl naturally, but check manually on warmer, sunnier days. The yellowed curd is still perfectly edible and the flavour is unchanged.

Browning from frost

A curd that was fine but turns soft, watery and brown after a cold night has been frost-damaged. Cauliflower curds can tolerate light frost but not a hard freeze. When a frost is forecast, cover the curd with fleece or simply harvest immediately. Early November cauliflowers are particularly at risk in temperate climates. Frost-browned outer sections can be cut away; the interior is usually still sound.

Watery brown patches from overwatering or disease

Brown, sunken or slimy patches spreading through the curd can indicate bacterial soft rot, particularly after a period of very wet weather or overhead watering. This is not recoverable — harvest immediately and cut out any affected portions. To prevent it, water at soil level rather than overhead, and ensure the bed drains freely after heavy rain.

Purple tinge on curds

Some white cauliflower varieties develop a purple or pink tinge when exposed to cold. This is an anthocyanin response — harmless — and usually disappears on cooking. It does not indicate disease. True purple cauliflower varieties like Graffiti are bred for this colour and it intensifies with cold. If the tinge is accompanied by softness or an off smell, check for frost damage rather than dismissing it as cosmetic.