Why do cabbages exist? What is the point of having a tight bundle of leaves that don’t attract pollinators and shield each other from the sun? Does its structure affect its ability to photosynthesise?
Jan Horton, West Launceston, Tasmania, Australia
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Cabbages exist because humans domesticated them long ago due to them being easy to grow in many climates and keeping well, especially when fermented. To me, and to many others, they also taste delicious, but not all my family agree.
Humans have bred the cabbage so that the juvenile stage is prolonged, because the light inner leaves are sweeter and more digestible than the tough, protective, dark green outer leaves. Once picked, they can be stored for a long time in a cool place, which is all to the good of humans and livestock. However, for the good of the plant, just leave it in the ground and keep watering it. In due course, it will develop a flowering stalk, then masses of flowers followed by lots of seeds.
“The cliffs are covered in wild cabbages descended from garden escapes, and you can smell them far out at sea”
Some relatives of the cabbage are grown for their seed, including canola, which is bred for its high seed oil content.
Jonathan Wallace, Fenham, Newcastle upon Tyne, UK
The tight rolled-up “head” of cabbage leaves doesn’t confer an advantage to the plant, any more than vines “benefit” from having seedless grapes. It has been bred to have characteristics desirable to the grower and consumer.
As to whether the structure of the cabbage affects its ability to photosynthesise, leaves that are inside the head and not exposed to sunlight can’t photosynthesise. But cabbages are able to grow to a large size, so the leaves that are exposed to the sun must be able to make enough carbohydrate to meet the needs of the whole plant.
Chris Warman, Hinderwell, North Yorkshire, UK
Cabbages exist to be eaten, as do cauliflower, broccoli, kale and Brussels sprouts. They are all cultivars of Brassica oleracea, a plant that grows wild on the sea cliffs of southern Europe.
Cabbages with a “heart” – the capitata type, as described by the questioner – are just one of seven main groups of cabbages, which in their turn contain innumerable varieties.
Selective breeding of cabbages may go back for as long as 4000 years and classical writers such as Theophrastus and Pliny the Elder described cultivated varieties, probably loose bundles of leaves resembling collard greens or what the British know as “spring greens”. Hearted cabbages were first developed in the Middle Ages.
The original attraction of cabbage is that its thick leaves stored carbohydrates and vitamins through the winter. Wild cabbage is tough and bitter, but natural variations enabled breeders to select for a softer, sweeter leaf. Breeders could also develop curly leaves (kale) and colours ranging from near black (cavalo nero) to near white.
Features that make cabbages desirable to humans would not be advantageous in the wild. This is true of most of our domesticated plants and animals, which are vulnerable to predators and adverse conditions. The modern cabbage needs continual protection from encroaching weeds, ravenous birds and cabbage white butterflies.
The tight heart of capitata cabbages exists because it is supported by the original loose cluster of green leaves that are trimmed away in harvesting. This can be seen in all its glory in exhibition cabbages, which can exceed a metre wide and be as heavy as a small person.
Wild cabbage is a slow-growing biennial or perennial with leathery leaves, sometimes tinged with violet, and masses of yellow flowers. It doesn’t compete well with faster growing plants, but it tolerates salt and finds a niche on chalk and limestone cliffs. The cliffs at Whitby and Staithes in the UK are bright with their flowers and you can smell them far out at sea. Genetic analysis shows these aren’t the original species. Instead, they are apparently descended from garden escapes.
Incidentally, lettuce has followed a similar course of development to cabbage, although only in the growth of its leaves, which may form heads or be curly and brightly coloured. It was adored by the ancient Egyptians and , the god of fertility and harvest.
David Muir, Edinburgh, UK
The cabbage as we know it isn’t a natural thing. Over thousands of years, inventive farmers have altered various structures of the wild cabbage.
Selective breeding for specific parts of the plant’s structure has given us particular vegetables: development of the terminal bud gave us cabbages; the lateral buds, Brussels sprouts; the flowers, cauliflower and broccoli; the leaves, kale and collard greens; and the stem, kohlrabi.
Some cultivars of Brassica oleracea may be of medical benefit. Brussels sprouts and broccoli contain sinigrin, a chemical shown to have . The bits of the plant that aren’t so green also contain valuable nutrients, even if they lack the green chlorophyll required for photosynthesis. Eat your greens!
Jackie Jones, Brighton, East Sussex, UK
These plants provide a breeding ground for cabbage white butterflies, which lay their bright yellow eggs in neat patches all over the underside of the leaves during summer months until October.
The caterpillars that hatch from these eggs eat large holes in the leaves. Only close-mesh net will protect the members of the cabbage family from the butterfly; they are attracted by the smell of the plant and will travel a long distance to find them.
I made the mistake of growing a summer-harvesting broccoli once and spent ages picking out these pesky caterpillars. I now only grow winter greens; by this time the butterflies have long gone.
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