GrowingHQ
Physiological disorderWhole plantStemsFlowers

Bolting

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.

What brings it on

Triggers differ by crop and this is why generic advice fails. Lettuce, spinach and coriander bolt mainly in response to lengthening days and heat. Beetroot and onion bolt after a cold spell early in life, which the plant reads as a winter it has survived.

source

Sourced guidancehigh confidence

  • Royal Horticultural Society: Bolting
  • Home and Garden Information Center — Clemson Cooperative Extension: Bolting in vegetable crops

Checked 2026-08-13

Usually seen: May, June, July, August

Preventing it

Ordered by how much difference each measure actually makes, not by how often it is repeated.

  • Sow in the season the crop is bred for, and use bolt-resistant cultivars for out-of-season sowings. This does more than any cultural measure.
    source

    Sourced guidancehigh confidence

    • Royal Horticultural Society: Bolt-resistant cultivars

    Checked 2026-08-13

  • Avoid checks to growth: dry soil, root disturbance at transplanting and long spells in a module tray all bring bolting forward.
    source

    Sourced guidancehigh confidence

    • Royal Horticultural Society: Bolting — cultural causes

    Checked 2026-08-13

  • For beetroot and onion, do not sow or plant so early that the young plants sit through a cold spell. The gain from an early start is lost if the crop runs to seed.
    source

    Sourced guidancehigh confidence

    • Royal Horticultural Society: Onion and beetroot bolting

    Checked 2026-08-13

  • Sow little and often through summer for salad crops, so there is always a young batch coming and no single sowing has to last.
    source

    Horticultural consensusmoderate confidence

    • Royal Horticultural Society: Successional sowing

    Checked 2026-08-13

Dealing with it once it is there

  • A bolted plant does not come back. Harvest what is usable at once — bolted lettuce turns bitter within days, a bolted beetroot goes woody — and sow a replacement rather than waiting.
    source

    GrowingHQ editorial positionhigh confidence

    GrowingHQ's practical position. The underlying physiology is not in dispute; what to do about it in a garden is a judgement.

    • GrowingHQ editorial synthesis — GrowingHQ

    Checked 2026-08-13

  • Bolting herbs are worth leaving to flower. Coriander seed is a crop in its own right, and the flowers of bolted herbs feed hoverflies whose larvae eat aphids.
    source

    Horticultural consensusmoderate confidence

    • Garden Organic — Garden Organic (Henry Doubleday Research Association): Beneficial insects in the vegetable garden

    Checked 2026-08-13

What it affects

Signs that lead here

Each of these lists the other things that produce the same sign, and how to tell them apart.

On sprays and treatments

GrowingHQ does not tell anyone what to apply, at what rate, or how often. Pesticide approvals differ by country, change without notice, and the product label is legally binding — it is also the document you are holding. What is described here is cultural and physical control, which is what a home grower can act on without a label in front of them.

Plant-specific guides

Where this is one of several causes that look alike on a particular plant, GrowingHQ publishes the differential rather than the general answer.