Bolting
also called Running to seed, Premature flowering
A plant deciding it is time to flower rather than time to feed you — the lettuce shoots up, the leaves turn bitter, and there is no way back.
- A sudden vertical stem shooting up from the middle of a lettuce, spinach or brassica, sometimes ten centimeters in a few days.
- Leaves turning bitter, tough and milky when cut, and the heart opening out.
- Onions throwing a hard round flower stalk up the middle of the neck, so the bulb will not store.
- Coriander and rocket flowering within weeks of sowing, with the leaves narrowing to feathery strips.
- Beetroot, carrots and Florence fennel putting up a flower stem instead of swelling their root or bulb.
Flowering is what the plant is for; the leaf or the root you wanted is only the stage before it. What triggers the switch differs by crop — heat and long days for lettuce and spinach, a cold spell for onions, beetroot and brassicas, and any sharp check for coriander and rocket. Once the plant has read the signal and switched, the decision is chemical and irreversible.
A hot spell in early summer for the salads, a cold snap after planting out for onion sets and brassicas, and drought or root disturbance for almost everything. Long days from midsummer bring on spinach and rocket whatever the temperature.
- There is no reversing it. Pull the bolted plant and sow a replacement, or leave it to flower deliberately.
- Pick and use the leaves at once — they are edible for a few days more, only bitter, and better cooked than in a salad.
- Use bolted onions immediately in the kitchen; they will not keep, but they are perfectly good now.
- Let a few bolted coriander, rocket and dill plants flower for the hoverflies and then collect the seed.
- Cut a bolting lettuce off at the base — a few cultivars will send up a modest second flush of leaves.
- Sow bolt-resistant cultivars, which exist for lettuce, spinach, beetroot, Florence fennel and onion.
- Sow little and often rather than one large sowing, so there is always a young plant coming.
- Water steadily and mulch; drought stress is the commonest trigger of all.
- Give summer salads afternoon shade, or grow them in the shadow of taller crops.
- Plant onion sets and brassicas after the cold snaps, and do not leave transplants pot-bound and checked in their trays.
The Cottage Garden Companion — the gardener's apothecary at cottagegardencompanion.com