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Iceberg lettuce in short supply – other leafy greens can fill the gap

Modern lettuces are grown a long way from where they are consumed, and genetically are a long way from their ancestors.

By Gail Taylor, Annabelle Damerum, Nikol Voutsina and Hazel Smith

The iceberg lettuce shortage is a reminder of just how we have come to take the 365 day supply of fresh fruit and vegetables entirely for granted. Certainly, in northern Europe this never-ending salad bowl is central to the push for a healthy diet. How did we manage in those years without a constant supply of asparagus, peppers, and a whole array of leaves delivered washed, prepared and packaged for our latest recipes?

Salad leaves and vegetables.
Iceberg lettuces are not the only leaves Image: Ekaterina Grigoreva / 123RF

Behind their delivery lies an industry glimpsed by few, but driven by vast industrial-scale growing farms in Spain and Portugal that can usually dodge the winter weather of the UK. Each week, several million salad leaves are grown and harvested, transported back to the UK, washed, prepared, and packaged and moved to the supermarket.

Ideally, this occurs with the whole supply chain under refrigeration, so a lettuce plant germinated and sown in Portugal can end up on the supermarket shelf up to eight weeks later, where it might have a shelf life of a single week. Each week throughout the year new crops are sown and, given that they have a very limited shelf life, it doesn’t take too much to upset this delivery giant.

Iceberg lettuces
Iceberg lettuces. Photo: Arbyreed / Flickr

Iceberg lettuce is known botanically as Lactuca sativa, which is a member of the sunflower family. Lac is derived the Latin for milk, but the white liquid which drips from cut stems of wild lettuce is actually now known to be natural latex.

Lettuce is at a crossroads right now as scientists prepare to publish the first full genome sequence of this salad crop, following several years of work from University of California at Davis, alongside a consortium of academics and big seed producers. Lettuce is consumed across the globe, with the Californian lettuce industry alone valued at over $2 billion, and China producing over 12 million tonnes each year. With all that production, we can’t afford to use precious land and not produce a nutritious crop – right?

Lactuca serriola
Lactuca serriola. Photo: United States Geological Survey / Wikipedia

First cultivated in Egypt, lettuce occurs naturally in many different varieties, known as cultivars. These cultivars are thought to originate from a single ancestor – the prickly lettuce Lactuca serriola. It’s hard to imagine that plant breeding over several centuries has moved us from this prickly lettuce to what we now know as ‘iceberg’, but during that process, much of the nutritional value in the dense green leaves, packed full of chemicals to defend plants from insect damage has somehow been lost. Iceberg lettuce is 95% water with little in the way of mineral and fibre.

Since the age of the 1980s prawn cocktail, the death of the iceberg lettuce has long been predicted, and although sales have declined, it still remains incredibly popular – cool and crisp. But the superior nutritional benefit of eating a range of dark leaves is clear. Spinach, watercress and wild rocket all contain significantly more nutrient punch than iceberg (vitamin content and also anti-oxidant potential), as does the ancient prickly lettuce. These alternative leafy crops even grow in much of the winter in the UK – mustard leaves, watercress and leaves of the cabbage family. So maybe we should rethink the iceberg once again, and take this opportunity to search out new leaves.