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What is bolting?

Published on October 27th 2020
A close up of a flower
A common phenomenon in the summer vegetable garden is bolting - when crops produce a flowering stem prematurely before it can be harvested.
Bolting is the plant’s natural attempt to produce seeds and reproduce, however, by investing more energy in flower and seed production, the leaves become bitter-tasting and result in poor quality produce.
A green plant in a garden

Why do plants bolt?

Bolting is a result of a change in temperature and day length, further accelerated by heat and water stress.
Hot weather and longer days flip the switch in the plant to rapidly produce flowers and seed and forsake leaf growth. This is very common in cool-season crops - as the weather gets above where the plant will survive, it hastens to reproduce before its time runs out.
Some biennial vegetables bolt in response to cold weather, where a sudden cold spell in spring can signal that winter has come and gone and it’s now time to shoot seeds for the upcoming season. This is often the case when plants are started off too early.
A pink flower on a plant

Which plants are prone to bolting?

Edibles most at risk of bolting tend to be leafy crops that thrive in cooler temperatures. Crops inclined to bolt include basil, arugula, lettuce, spinach, cabbage, celery, leeks, onion, carrots, turnip and beetroot.
A close up of a tree

How to prevent bolting

Occasionally, if caught in the very early stages, bolting can be temporarily reversed by cutting off the flowers and flower buds. Some plants, like basil, will cease bolting and resume producing leaves. In other plants though, like lettuce and broccoli, removing flowers only allows for some extra time to harvest the crop before it becomes bitter.
Here are a few things you can do to keep your crops from bolting:
  • Select bolt-resistant varieties.
  • Offer shade to cool-season crops.
  • Ensure the soil is healthy. Soil with sufficient nutrients and balanced moisture levels will encourage rapid growth.
  • Keep soil temperature down by adding a layer of mulch and watering regularly.
  • Harvest outer leaves to keep plants from maturing.
  • Time the planting of cool-season vegetables for either early spring or late summer so vegetables can mature in cooler weather.
A plant in a garden

What to do when plants have bolted?

It’s not the end of the world! There will surely be a few leaves left to salvage and mix in with salads. Chop up root vegetables and use in soups or stews.
Bolted vegetables are a feast for pollinating insects, including bees, and a floriferous tinge of beauty for you to enjoy!
A close up of a flower

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