Lettuce bolting: can you eat bolted lettuce?

Like every living thing, lettuce needs to ensure its continued reproduction. This is why lettuces “bolt” – the plants begin to grow upwards, producing less leaves and eventually blooming.

As the days grow longer and warmer in spring and summer, growing conditions are optimal, and your plants will really start to come into their own. While lettuce plants enjoy the added warmth and sunlight too, it is these two components that may encourage your plant to bolt. Where yesterday you may have had a plump, perfectly formed lettuce head, today you have an elongated, flowering lettuce. Find out what all this means and whether you can prevent lettuce from going to seed prematurely, in the article below. We also answer the question of whether bolted lettuce is edible.

Why does lettuce bolt?

It is important to know that lettuce bolting is perfectly normal. It is all part of the plant’s natural development. Like most plants lettuce reproduces from seeds, so after germination lettuce plants enter the vegetative stage where leaf growth occurs, and we can enjoy the plump round head as a salad once they are fully formed. From there it moves into the generative (bolting) stage – this can occur quite suddenly in some cases – where the plant begins to grow upwards and produce the flowers so vital for the plant’s future growth.

Plants need certain stimuli to make the transition into that generative phase. Many lettuce varieties are classed as long-day plants, meaning that they automatically start to bolt when there are more than 14 hours of daylight. Other lettuce plants react in the same way when the right temperature has been reached. However, some lettuce plants flower prematurely. The reason for this is usually that the lettuce plant has been under some sort of environmental stress – exposed to heat, cold or drought for example. Pest infestation or disease are two further causes.

Tip: There is a lettuce variety suitable for every season. Iceberg, romaine and batavia lettuces grow well almost all year round, although when they days are longest towards mid-summer, they may bolt early starting to flower before the head is fully formed. They do tolerate the odd frost, which is why they should be the first lettuce you plant in the bed. Cos (Lactuca s. var. longifolia) or lamb’s lettuce (Lactuca s. var. crispa) plants are more suitable for the warmer months and should be planted from May onwards. These tolerate the high temperatures in summer. Endives and chicory (Cichorium) are suitable for autumn cultivation, as well as crisp winter lettuce varieties (Lactuca sativa var. capitata nidus jaggeri). You can find more details in our related article on cultivating lettuce.

Can you prevent lettuce from going to seed?

Flowering is part of the natural development of lettuce plants so at some point, all lettuce will run to seed. This means that if you leave lettuce in the bed too long, bolting is inevitable. However, there are big differences in varieties as far as the timing and tendency to bolt early are concerned. You can help prevent lettuce from flowering too early by eliminating as many stress factors as possible. We have put together some tips on this for you below.

How to prevent lettuce from bolting prematurely:

• Lettuce should only be sown at the right time for the variety.
• Make sure you have the right location. If the soil is too heavy for example, it is a good idea to mix it with sand to loosen it up. If the soil is very light, mix in some potting compost – such as our Plantura Organic Tomato & Vegetable Compost – before planting, which, among other things, improves the soil’s water retention.
• Do not overcrowd the bed. Spread the plants far enough apart so that they do not have to compete for light, water and nutrients.
• Remember to water your lettuce plants regularly.
• If planting in late spring or summer, do this in partial shade as extreme heat can result in lettuce bolting.
• Choose a heat-tolerant variety of lettuce when planting in a greenhouse. High summer temperatures in a greenhouse can cause lettuce to bolt prematurely. Regular ventilation of the greenhouse will also help.
• Use high-quality lettuce plants from a trusted supplier. Lower quality seedlings often tend to bolt early.
• Plant them at the right time (not too late) and ensure a continuous supply of water and nutrients in the early stages of propagation.

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Can you still eat bolted lettuce?

In theory, bolted lettuce is still edible and non-toxic, however a taste test is always a good idea. The leaves tend to become tougher, more bitter and may not be enjoyable. The plant builds up bitter substances to make them less appetising for predators. Bolted lamb’s lettuce and flowering lamb’s lettuce are also edible. However, the same applies here: taste it first.

Tip: If your lettuce has bolted, you can leave it in the bed and harvest the seeds once it has flowered. Always harvest your seeds from the largest, best looking heads to get the best future crop. If you take seeds from smaller lettuce heads that have bolted prematurely, it is likely they will yield plants with similar characteristics. If you leave the lettuce plants to themselves, there is a chance that they will self-seed.

The choice of variety is a key factor in preventing lettuce plants from bolting. And variety is the spice of life, so why not mix it up a bit in your veg patch and grow a selection of lettuce throughout the year.