Onion Bolting

Onions bolting in a field

Bolting is the growth of an elongated stalk with flowers grown from within the main stem of a plant. This condition occurs mainly in plants that are grown for their leaves, such as cabbage, lettuce, spinach, and other leafy greens. Bolting is induced by plant hormones of the gibberellin family. Bolting occurs because of the photo period. Some plants are long day plants (LDP) while others are short day plants (SDP) and some are day neutral. When a LDP such as spinach receives light for a longer period than it is dark for then it will bolt, otherwise known as flower. Bolting will affect many plants by causing unsatisfactory storage (onion),[1] and poor taste (lettuce).


Plant grows a central stalk with flower head/heads or bulb present. Leaf production is reduced.


Cut off flower stalk. Follow preventative methods to stop other plants bolting.


Bolting can be caused by growing in the wrong season (early or late planting), extreme weather such as a long, hot summer or cold spring or by planting in loose soil. Keep the soil and roots cool during hot weather. Try shading, watering regularly and mulching to preserve water.[2]



  1. Hessayon, D.G. (2009). The Vegetable & Herb Expert. Transworld Publishers, London. p. 74. ISBN 9780903505468
  2. (2010). Bolting Broccoli: Growing Broccoli In Hot Weather. Gardening Know How. Retrieved: 2010-07-28.
This page uses Creative Commons Licensed content from Wikipedia (view authors).