Broccoli: plant running up to flower before it is ready to eat

What it is likely to be on broccoli

1. Transplant shock

   Candidate 1common on this plant

   ·source

   Sourced guidancemoderate confidence

   • Royal Horticultural Society: Transplanting

   Checked 2026-08-13

   Wilting, leaf drop or a stall in growth in the days after repotting, planting out or moving. Often not a problem at all but a normal adjustment, and the commonest mistake is to react to it by changing something else — which turns a recoverable check into a real decline.

   Points towards it

   • · a check at transplanting is a distinct trigger from heat, and it acts weeks earlier in the season
   • · it follows planting out from modules or a seedbed

   Argues against it

   • · hot weather is the commoner trigger and points to ordinary bolting rather than to a transplant check
   • · the plant has not been moved, so a transplant check cannot be the trigger — this rules it out entirely.

   Check this next

   Work out when it was moved. A crop that runs to seed within a few weeks of being planted out, before any hot spell, was checked at transplanting — root disturbance and a dry fortnight afterwards do it as reliably as heat.

   What to do now

   Nothing rescues the affected plants; harvest what is usable. Next time sow direct where the crop is to grow, or plant out earlier and smaller and water well for the first fortnight — the aim is to avoid the check rather than to treat the result.

   ·source

   Sourced guidancemoderate confidence

   • Royal Horticultural Society: Transplanting

   Checked 2026-08-13

2. Bolting

   Candidate 2common on this plant

   ·source

   Sourced guidancehigh confidence

   • Royal Horticultural Society: Broccoli and calabrese — cultivation
   • Agriculture and Horticulture Development Board — AHDB: Brassicas — bolting and crop timing

   Checked 2026-08-13

   A plant switching from leaf or root production to flowering and seed. It is the plant doing exactly what it evolved to do under stress, and it cannot be reversed — which makes bolting a problem of timing and cultivar choice rather than of treatment.

   Points towards it

   • · calabrese responds to heat by opening its head into flower within days, which is why a summer crop can be lost over a weekend
   • · a plant short of water in a hot spell runs far faster than one that is kept damp
   • · the whole planting responds to the same weather at the same time
   • · it is a response to summer weather in an open bed

   Argues against it

   • · cool weather is what holds a broccoli head tight, and a cold spell makes this much less likely
   • · a plant that ran up within days of transplanting was checked by the move rather than by the weather

   Check this next

   Look at the head with a hand lens before deciding whether it has gone. Heat opens a calabrese head from the centre outwards — the beads separate, the stalks between them lengthen, and yellow petals show at the middle first — and it happens across the whole planting in the same few days of hot weather. A head that is still tight and dense at the centre has not bolted yet and can be cut today. A plant that ran up soon after planting, with no head worth speaking of, was checked at transplanting instead.

   What to do now

   Cut every head that is still tight, immediately, rather than waiting for them to size up — a small tight head is worth having and a large open one is not, and in hot weather the difference is two days. Then leave the plants in: calabrese produces useful side shoots for weeks after the main head is cut. For the next crop, water heavily in dry spells, mulch, and time the sowing so the heads mature in September rather than August, which removes the problem entirely in most seasons.

   ·source

   Sourced guidancehigh confidence

   • Royal Horticultural Society: Broccoli and calabrese — harvesting
   • Garden Organic — Garden Organic (Henry Doubleday Research Association): Brassicas — timing summer crops

   Checked 2026-08-13

Narrow it down

This page lists everything at once, which is the right shape for reading and the wrong shape for deciding. The interactive tool asks one question at a time, starting with whichever would separate these causes fastest, and stops as soon as further answers would not help.

Opens with the plant and the symptom already set. Nothing you answer is stored or sent anywhere — the answers live in the address bar and nowhere else.

What this does not cover

These are the causes GrowingHQ holds rules for on broccoli — not every cause there is. Where several problems look alike, the honest answer is often that they cannot be told apart by eye, and a page that named one would be guessing. If none of the above fits, the general plant running up to flower before it is ready to eat page lists causes across all plants, and the Broccoli profile lists the problems it is prone to.