Bolting

Bolting is when a plant switches from growing leaves to making flowers and seed before you want it to. The plant is doing exactly what nature intended — reproducing — but it does so too early, ruining the part you actually wanted to eat. Once a leafy crop bolts, energy rushes into the flower stalk, the leaves turn bitter and tough, and the growth you'd hoped to harvest is effectively over.

Which crops bolt

The usual culprits are fast-growing leaf and root crops:

• Lettuce, spinach and rocket — the classic bolters, especially in summer heat.
• Coriander — notoriously quick to run to seed.
• Beetroot and onions — these can bolt after a cold shock early in the season.

What triggers it

Bolting is the plant's stress response. Common triggers in a UK garden include:

• Heat and drought — a warm, dry June or July is the biggest cause.
• Long days — lengthening daylight tells many crops it's time to flower.
• Cold shock — a late frost or cold snap after sowing can trip beetroot and onions into bolting later on.
• Transplant stress — roots disturbed during planting out, or seedlings left too long in small pots, can prompt an early dash to seed.

How to spot it

Look for a central seed stalk rising from the middle of the plant. Lettuce loses its tight heart and stretches upward; spinach and rocket send up a thin flowering spike; coriander produces lacy white flower heads. Once you see that stalk, the leaves below it will already be turning bitter.

How to prevent it

You can't stop hot weather, but you can lower the risk:

• Choose bolt-resistant varieties — seed packets often say "slow to bolt" or "bolt-resistant". Well worth seeking out for summer sowings.
• Water consistently — steady moisture matters more than occasional soakings, as dry roots are a major trigger.
• Sow little and often — successional sowing every two or three weeks means you always have a young, un-bolted batch coming on, rather than one big crop that bolts all at once.
• Give some summer shade — a little afternoon shade in the hottest weeks keeps salad leaves cooler and slower to run up.

When bolting is fine

Not every bolted plant is a loss. Left to flower, rocket, coriander and brassicas produce blooms that pollinators love, so a few bolted plants make a useful nectar source. You can also let them set seed and save it for next year, or simply leave them as a treat for the bees. Unlike a true perennial, these are annuals racing to finish their life cycle — so once they've bolted, pull most of them, sow a fresh batch, and keep the salad bowl topped up.