Bolting (running to seed)
Leafy crops and roots flower when the season tells them to: longer days, a hot spell, drought, or a cold snap for biennials. Once a stalk rises the plant puts its energy into seed, and the leaves or roots you wanted decline fast.
Light & temperature
What it looks like
The shape of the plant changes before the flowers open.
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A rising centre Leaves stop forming a rosette and a stalk pushes up from the middle. -
Narrow upper leaves New leaves are small, pointed and far apart on the stalk. -
Bitter taste Lettuce and spinach leaves turn bitter and tough, with milky sap in lettuce. -
Flower heads Coriander, dill and brassicas open flat or branched heads of small flowers.
How to confirm it
Bolting is visible; the work is finding its trigger.
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Sowing date
Summer sowings of spinach and coriander bolt quickly as days lengthen.
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Recent weather
A hot or dry spell in the last fortnight is the usual trigger in leaf crops.
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Cold after planting
Onions, beet and cabbage sown or planted very early can bolt after a cold spell.
What to do
The plant will not return to leaf. Make the most of it.
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Harvest now
Pick usable leaves or roots straight away before they coarsen further.
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Snap the stalk
On onions, pinch out flower stalks and use those bulbs first; they will not store.
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Leave some to flower
Coriander seed, dill heads and brassica flowers are useful, and feed pollinators.
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Resow
Sow again little and often, choosing bolt-resistant varieties for summer.
Prevent it next time
- Sow cool-season crops in spring and late summer, not midsummer.
- Keep soil evenly moist and mulched.
- Sow coriander and dill where they are to grow; they bolt when transplanted.
- Choose varieties labelled slow- or bolt-resistant.
What not to do
Do not cut the stalk off lettuce or spinach hoping for more leaves; the plant simply sends up another.
In the growing guides
Where the guides mention it, with plant-specific advice.
Sources
- Lettuce bolting, Purdue Plant and Pest Diagnostic Laboratory