Bolting

Bolting refers to a plant's rapid vertical growth followed by flowering, usually triggered by heat, long days or stress factors. This phenomenon particularly affects leafy and root vegetables such as lettuce, spinach, rocket, coriander or winter radish.

Instead of continuing to produce leaves or storage organs, the plant switches into its generative phase - it puts its energy into forming flowers and seed.

What happens during bolting?

• The stem elongates significantly
• The internodes lengthen
• A flower spike forms
• Leaves often become smaller, tougher or bitter

In lettuces and herbs especially, this considerably lowers harvest quality.

Causes of bolting

Bolting is a natural response to environmental conditions. Common triggers are:

• High temperatures
• Long day length (many vegetable varieties are long-day plants)
• Drought stress
• Nutrient imbalance
• Sowing too early in spring, followed by a cold spell
• Variety-specific predisposition

Botanically, this is the transition from vegetative growth to the flowering phase. In German, this process is referred to as Schossen.

Why does the plant "decide" to bolt?

Bolting is a survival mechanism. When environmental conditions become unfavourable, the plant tries to set seed as quickly as possible to ensure the survival of its species.

For gardeners, however, this usually means the plant turns tough, pungent or bitter - and becomes largely unpalatable.

How can bolting be avoided?

• Choose suitable sowing dates
• Use summer-tolerant or bolt-resistant varieties
• Ensure even watering
• Make use of light partial shade in high summer
• Harvest promptly