Why does the lettuce bolt?

green leaf lettuce
green leaf lettuce

Have you ever wondered why your lettuce suddenly shoots up in the summer? Here’s what’s behind it, and here’s how you can prevent it.

Lettuce from your own garden is a delight. If you plant different varieties of lettuce, you can continuously harvest tender leaves and thick heads until autumn. With proper cultivation planning, you can also avoid bolting of the lettuce. Find out which varieties are particularly resistant to bolting and what exactly happens when lettuce “shoots”.

Why “shoots” the lettuce in the summer?

Head and leaf lettuce are annuals, which means that within a few months the plants go through their entire life cycle of development, from germination to seed formation. After sowing or planting, they form a dense rosette of leaves. Most butterhead lettuces are long-day plants, and a day length of more than 12 hours triggers flower formation. Then the central shoot stretches and “shoots out”. At a height of about 50 centimeters (20 inches), the stem branches and several man-sized inflorescences with small, pale yellow flowers appear. The leaves then become chewy and taste quite bitter at the base of the stem.

Usually, you pull the heads out as soon as the center shoot stretches. If you want to gain seeds yourself, mark the most beautiful lettuces in the bed and let them blossom. Mark only firm heads that remain compact for a long time. If you select early bloomers, you are selecting for “bolters”. Inflorescences form in June and July. The numerous seeds ripen between July and August, and if you are not careful, they fly away with the wind. It is better to pluck them out early or wipe them off by hand over a sieve and let them dry in an airy place.

Which lettuce variety should you choose?

Anyone who sifts through the many colorful seed bags in the spring for suitable varieties for the garden is spoiled for choice. Whether butter tender butterhead lettuce, hearty leaf lettuce or refreshingly crunchy iceberg and batavia lettuce: they all belong to the same plant species (Lactuca sativa). Impatient amateur gardeners simply reach for pre-cultivated young plants; for those who want to enjoy the whole variety of lettuce, sowing and pre-cultivation is worthwhile, because here the selection is much larger. Despite the tempting novelties, the common lettuce has not lost any of its popularity. And rightly so, because especially proven early varieties such as ‘May King’ or ‘Victoria’ convince with butter-tender, soft outer leaves and a crunchy, tender-yellow, firm heart.

There is much to be said for growing lettuce: Even a normal portion of lettuce provides a quarter of the daily requirement of vital folic acid, a B vitamin necessary for all human growth and development processes. The fact that the content of other vitamins, minerals and secondary plant substances also decreases a short time after harvesting is no reason to give up eating it, but speaks all the more in favor of growing it in your own garden. Because then you can always harvest fresh lettuce and consume it directly. But what do you do in the summer, when the length of the day significantly exceeds 12 hours? It’s quite simple: you reach for varieties that are resistant to bolting. Because so you can harvest lettuce even in the summer months, plant breeders have developed day-neutral varieties. For summer cultivation, therefore, choose only bolt-resistant varieties such as ‘Lucinde’, ‘Ovation’ or ‘Pirate’.

Because the plants develop at different rates depending on the temperature, experienced gardeners do not sow new lettuce every two to three weeks, as is often recommended, but reach for the seed bag each time when the previously sown plantlets have developed the first two to three true leaves.

watering lettuce can prevent it from bolting to soon
watering lettuce can prevent it from bolting to soon

How to prevent lettuce from bolting?

The most important thing in advance: even lettuces that have grown in height and form flowers are still edible. However, you should taste before preparing to make sure that the leaves have not become chewy or bitter. You should remove the hard stem completely. But not only the length of the day affects the shooting: Indeed, the reason may also be stress. This can occur, for example, if the lettuce plants are too warm or too dry, or if they are too close together. This can be prevented by good care, adequate spacing and timely harvesting – especially in hot weather.

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