Check these first
- Does the browning start at the leaf edge, from a spot, or from the lowest leaves?
- Are there black specks, powder, or mould on the dead tissue?
- Did you fertilize, spray, or have a heatwave just before it started?
Most likely causes
From the pests and diseases recorded for this plant, the ones whose symptoms match, most serious first. Symptoms alone rarely confirm a cause, so use the linked page to check the signs and treatment.
Black Rot
V-shaped yellowing spreads inward from the leaf margins and the veins darken into a black network. As it advances the whole plant wilts and dies.
General description; not specific to this plant.
How to identify and treat: Black RotDowny Mildew
Pale yellow to yellow-brown angular lesions form on the upper leaf surface with a gray-purple mold in the matching spot underneath. Lesions merge, the leaves die back and the plant declines early.
General description; not specific to this plant.
How to identify and treat: Downy MildewSclerotinia Rot
The crown, stem or head rots in a water-soaked way and is covered in white cottony mycelium. Black sclerotia later form inside and on the surface, and the plant wilts and dies.
General description; not specific to this plant.
How to identify and treat: Sclerotinia RotOther possible causes
The three above are the causes on record for this symptom.
Other symptoms on this plant
What other growers did about it
A page like this one can tell you what romanesco broccoli leaves turning brown and dying is and what to try. What it cannot tell you is what actually happened to someone who had it on the same plant, at the same point in the season, and what they did next.
Gadenin is a free garden journal built around that. You photograph the plant, tag what you are seeing, and the entries line up by date for each plant you grow.
- Tag the problem and the app tells you how many other growers have logged the same thing on the same plant.
- Growers who make their records public can be followed, so you can read what they did and how it turned out.
- Next season your own entries come back at the same point in the year, so you check the plant before it starts.
Free on iPhone. Recording, tagging and reading public records cost nothing.