Bolting (Premature Flowering)
Risk near you, next 48h
See whether your local forecast favours this disease right now.
When it strikes
Fix the cause, not the leaf
No spray will help here. The trigger is soil, water supply, nutrition or temperature, so change the growing condition and judge the result on new growth, not on damaged leaves.
Not contagious
Nothing spreads from plant to plant here. Neighbouring plants showing the same signs are reacting to the same soil, water or weather, so fix the cause rather than isolating plants.
Safe to compost
No pathogen carries over on this material, so it can go on an ordinary heap with the rest of the garden waste.
When and where to look
Scout the planting once temperatures pass 25°C, in dry air below 50%.
Rule these out first
Same category, and at least one host crop in common — so they are genuinely confusable in the same part of the garden.
The signs that lead here
Full problem lists for these crops
About
Bolting is a plant deciding it is running out of time and switching from leaf or root growth to setting seed. Heat, long days, drought, root disturbance and a cold spell in the seedling stage can all trigger it, and once it starts it cannot be reversed.
Symptoms
A tall flowering stem shoots up from the centre of the plant. Lettuce and spinach turn bitter and milky, onions and beetroot form a hard woody core, brassicas produce a thin stalk instead of a head, and coriander and rocket run to seed within days.
Organic Treatment
Pinch out the flower stem the moment it appears to buy a week or two of usable leaves, then harvest the whole plant. Keep the remaining crop cool and moist: mulch, water deeply and shade with mesh in a heatwave.
Chemical Treatment
There is no chemical control — this is a plant’s developmental response, not a disease.
Prevention
Sow at the right time for the crop, use bolt-resistant varieties, and never let seedlings dry out or sit in cold soil, which sets bolting off weeks later. Succession-sow small batches so a bolted row is a minor loss, and switch heat-sensitive crops to autumn sowings.
Crops at risk
Related problems
Bolting (Premature Flowering) risk by location
Each location has a month-by-month profile computed from the weather archive: how many hours a year actually meet this disease’s thresholds.