Bolting (horticulture)

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An example of lettuce bolting.

Bolting is the production of a flowering stem (or stems) on agricultural and horticultural crops before the crop is harvested, in a natural attempt to produce seeds[1] and reproduce. These flowering stems are usually vigorous extensions of existing leaf-bearing stems, and in order to produce them, a plant diverts resources away from producing the edible parts such as leaves or roots, resulting in a poor quality harvest. Plants that have produced flowering stems in this way are said to have bolted. Crops inclined to bolt include lettuce, basil, beetroot, brassicas, spinach, celery and onion.[1]

Bolting is induced by plant hormones of the gibberellin family,[citation needed] and can occur as a result of several factors, including changes in day length, the prevalence of high temperatures at particular stages in a plant's growth cycle, and the existence of stresses such as insufficient water or minerals. These factors may interact in a complex way.[1] Day length may affect the propensity to bolt in that some plants are "long day plants", some are "short day plants" and some are "day neutral", so for example when a long day plant, such as spinach, experiences increasingly long days that reach a particular length, it will be inclined to bolt.[2] Low or high temperatures can affect the propensity of some plants to bolt if they are experienced for sufficient periods at particular points in the life cycle of the plant; once these conditions have been met, plants that require such a trigger will subsequently bolt regardless of subsequent temperatures.[1] Plants under stress may respond by bolting so that they can produce seeds before they die.

Plant breeders have introduced cultivars of bolt-prone crops that are less prone to the condition.[1]


  1. ^ a b c d e Stefan Buczacki & Keith Harris (1998). Pests, Diseases & Disorders of Garden Plants. Collins. pp. 604–5. ISBN 0 00 220063 5. 
  2. ^ Zeevaart, J. A. D. (1971). "Effects of Photoperiod on Growth Rate and Endogenous Gibberellins in the Long-Day Rosette Plant Spinach". Plant Physiology. 47 (6): 821–827. doi:10.1104/pp.47.6.821. PMC 396778Freely accessible. PMID 16657712.