At Sea Spring Seeds, we are serious about bolting. And so we should be; bolting is an irreversible change that brings the productive lives of both root and leafy vegetables to a sudden and unceremonious end.

What is bolting?

Often used but seldom understood, the term ‘bolting’ refers to the elongation of the plant’s previously very compact stem. It signals a fundamental change in a plant’s life cycle, from the vegetative stage to the reproductive stage. Bolting is normally the first visible sign that a plant has made this switch, and is followed by a series of predictable steps including the development of a  flower head, seed production and finally death. All annual and biennial vegetables will go through this process.

To the vegetable gardener the longer a vegetable stays in the vegetative phase the more productive it is. Once bolting occurs the plant will not produce any more leaves and eventually become inedible.

The process can be seen very clearly in lettuces or any rosetted or hearted leafy vegetable.  If you look at an individual plant of these leafy vegetables, you will see that the leaves are arranged in a whorl around a short, almost indiscernible stem. At the very top of the stem, in the centre of the whorl, is a microscopic growing tip from which all new leaves are initiated. And as long as the tip produces leaves, the whorl remains intact, and the plant is said to be in a vegetative state.

Unfortunately, the vegetative state doesn’t last forever, and at some point a trigger stimulates the growing tip to stop producing leaves and switch to developing a flower head. The plant is then said to be in the reproductive state. 

When this happens, the plant undergoes the following visible changes:

  • A flower head develops, first noticeable as tight buds.
  • The short stem below the growing tip starts to stretch upwards like a car antennae, and the leaves attached to it then become spaced more or less equidistance along its length.
  • As the stem gets longer, the flower head is lifted upwards, and the tight buds open out into flowers.
  • Once pollinated the die off, followed in due course by the formation of seeds.
  • The plant dies

The trigger to switch to the reproductive phase can be external factors such as cold weather or water stress, but ultimately it is age. The plants have a finite life span, that’s why they are called annuals or biennials, and there is nothing that can be done to stop the plants eventually flowering. Given good growing conditions, there are, however, very large differences between varieties, with one lettuce bolting just a few days after it reaches maturity, while other varieties grown side-by-side staying vegetative (and productive) for weeks longer. 

To get the most out of their vegetables gardeners should always select varieties that are “bolt-resistant”, i.e. remain in the vegetative state for longer.

The dual nature of bolting

In the end, though, bolting is neither good or bad, it just depends on your perspective. From a gardener’s point of view, bolting is bad since the productivity of both leafy and root vegetables is brought to an end. From a seed producer’s perspective, however, bolting is good since the end product is seed, without which there would be no vegetable gardening. In the end, we all need bolting, just as long as it is delayed long enough for us gardeners to get some vegetables to harvest.


© Joy Michaud