Week 23 – Bolting

Bolting is the term used when a vegetable crop runs to seed. It is triggered either by a cold spell, a hot spell, or changes in day-length (photoperiod). Annual crops will bolt in the first year, biennials in the second year. Some vegetables (lettuce, mizuna, arugula, etc.) become unusable (bitter) once they bolt.

A tell-tale sign that a vegetable has bolted is the formation of a central stalk. Once you see this you know that the vegetative stage is over and the flowering stage has begun.

I recommend allowing one or two plants to bolt (lettuce and cilantro are good choices). This will not only give students an opportunity to view the complete life cycle of a plant, it will also enable the formation of seeds of which we can save for the following season.

Bolted Lettuce
Bolted Cilantro

Lettuce Bolting

In the heat of summer lettuce will bolt and shoot up a central stalk 3-4 ft high. After the plant flowers, seeds will form and can be collected for the following season. Currently we have been collecting seeds from coriander (cilantro), dill, fennel, lettuce, and pole beans; also from such flowers as: marigolds, cosmos, and sunflowers.