Kale has been cultivated for over 2,000 years. In much of Europe it was the most widely eaten green vegetable until the Middle Ages when cabbages became more popular. Historically it has been particularly important in colder regions due to its resistance to frost. In nineteenth century Scotland kail was used as a generic term for 'dinner' and all kitchens featured a kail-pot for cooking.
Our common cabbage-like vegetables provide an excellent example of remarkable crop improvements that was accomplished by simple long-term selection with no real goal in mind, but simply by people growing those plants that had the features that they most desired.
Although they appear very different, kale, cabbage, kohlrabi, cauliflower, broccoli and Brussels sprouts are all the same species of plant. These plants are all known botanically as members of the species Brassica oleracea. The only difference between these plants are the differences that were introduced over thousands of years of human cultivation and selective propagating.
In the wild, the Brassica oleracea plant is native to the Mediterranean region of Europe, and is somewhat similar in appearance to a leafy canola plant. Sometime, soon after the domestication of plants began, people in the Mediterranean region began growing this first ancient "cabbage" plant as a leafy vegetable. Because leaves were the part of the plant which were consumed, it was natural that those plants with the largest leaves would be selectively propagated for next year's crop. This resulted in large and larger-leafed plants slowly being developed as the seed from the largest-leafed plants was favoured.
By the 5th century B.C., continued preference for ever-larger leaved had led to the development of the vegetable we now know as kale. Kale is known botanically by the name Brassica oleracea variety acephala which translates to mean "cabbage of the vegetable garden without a head."
Kale continued to be grown as a leafy vegetable for thousands of years, and is still grown today. As time passed, however, some people began to express a preference for those plants with a tight cluster of tender young leaves in the centre of the plant at the top of the stem.
Because of this preference for plants in which there were a large number of tender leaves closely packed into the terminal bud at the top of the stem, these plants were selected and propagated more frequently. A continued favouritism of these plants for hundreds of successive generations resulted in the gradual formation of a more and more dense cluster of leaves at the top of the plant. Eventually, the cluster of leaves became so large, it tended to dominate the whole plant, and the cabbage "head" we know today was born.
Kale was grown as a staple crop in the the Scottish Islands due to it’s extreme hardiness, and was given protection from the elements in purpose built Kale Yards. Indeed, almost every house had a kale yard and preserved kale in barrels of salt, similar to sourkraut in Germany. They also fed it to livestock through the winter. Kale continued to be extremely important until potatoes came to the Islands towards the end of the 18th century.
Scorr Kale yard on the Isle of Skye remains in remarkably good condition with walls over 4 feet high, and with all doorways and gateways well defined but is a sad reminder of the depopulation of Skye in the 19th and 20th centuries
Early in the twentieth century, Kailyard (kale field) was a disparaging term used to describe a school of Scottish writers, including Peter Pan author J. M. Barrie, whose writing featured sentimental nostalgia for rural Scottish life.