Why Is My Broccoli Head Opening and Going to Flower?

Broccoli florets that start separating, buds that swell and turn from tight green buttons to visible yellow flowers — this is broccoli that has been left too long on the plant. The broccoli head is actually a cluster of immature flower buds, and when not harvested at the right time those buds continue to their natural purpose and open into flowers. The window between perfect harvest and full flowering is shorter than many growers expect, especially in warm weather.

How quickly broccoli heads deteriorate

A broccoli head in warm weather (20°C+) can go from perfect harvest to yellowing flowers in three to five days. In cool weather (below 15°C) the window extends to a week or more. This is why checking the broccoli patch every day or two during the heading season is essential — not paranoid. Many growers find that once a head starts to open, it progresses so fast that by the time they have noted it and returned two days later, it is fully flowered.

Identifying the right harvest moment

Harvest broccoli when the central head is fully formed — usually 10 to 20cm across depending on variety — the florets are still tightly packed, the head is firm when gently squeezed, and the colour is deep blue-green. Individual buds should be small and round, not visibly swollen or showing any yellow. The stem should be cut 10–15cm below the head to encourage side shoot development.

Is flowering broccoli still edible?

Yes. A broccoli head at the early flower stage — yellow buds just opening — is still edible and has a pleasant, more intense flavour. Cook it immediately as it will not keep. A fully-flowered head is technically edible but the texture becomes very soft and the flavour grassy. The flowers themselves are edible in salads. Cut the plant back to encourage side shoot production regardless of how advanced the flowering is.

Getting more from the plant after the central head

Once the central head is cut, most broccoli varieties produce a succession of smaller side shoots from the leaf axils. These side shoots are individually smaller but can be harvested over many weeks. Keep cutting them before they flower to prolong the harvest period. Feed with a balanced fertiliser after cutting the main head to support side shoot development.