Bolting
/ˈboʊltɪŋ/
Definition
Bolting refers to the rapid elongation of a plant’s flowering stem as it shifts from leafy growth to reproduction. It is most common in annuals and biennials grown for leaves or roots, such as lettuce, spinach, and onions. Once bolting starts, the plant directs energy into flowers and seed production, often causing leaves or roots to become tougher, smaller, or more bitter.
Biological Role
- Shift to reproduction: In many annuals and biennials, bolting marks a major developmental switch from leaf production to flowering and seed formation. Once this shift starts, energy moves away from edible or ornamental foliage.
- Common triggers: Day length, temperature, and plant age often interact to start bolting. Cool periods can trigger it in some crops, while heat and drought stress can speed it in others, especially leafy vegetables and herbs.
- Visible plant changes: A rapid stem elongation usually comes with smaller, tougher, or more bitter leaves in species grown for foliage. This change reflects altered growth hormones and the plant’s priority to complete reproduction.
- Why growers watch for it: For lettuce, spinach, cilantro, and similar crops, bolting often reduces harvest quality and market value. In seed production, though, it is necessary because flowers and mature seed cannot form without it.
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