When is a cabbage not a cabbage?

Not too long ago Deirdre Larkin of the Cloisters Museum (part of the Metropolitain Museum of Art) wrote an article on the cloisters blog, The Medieval Garden Enclosed, about Medieval colewort and kales which are part of the cabbage family. Since the Germans are well known cabbage lovers, and I spend a lot of my time reenacting Renaissance German I was delighted with the article, and intrigued with this part:

"Vegetables have changed far more since the Middle Ages than the medicinal plants or wildflowers grown here at The Cloisters, and it is more difficult for us to represent them accurately. The brassicas have changed the most. Our large, tight-heading cabbages do not much resemble the small loose-leaved medieval colewort." 

But today I was reading  Food in Medieval Times  by Melitta Weiss Adamson. Adamson had this to say about cabbage:

“Of European ancestry, cabbages were originally headless, and were eaten by the ancient Egyptians, Greeks, and Romans. Not until the first century B.C. do we hear of headed cabbages that may have been cultivated in northern Europe first. In the Middle Ages the headless kale, or colewort, was a staple food of the Scots, while headed cabbage was favored by the Dutch and Germans. Other varieties belonging to the cabbage family that were cultivated in medieval Europe, especially in Italy, were cauliflower and broccoli. Headed cabbage was usually boiled or made into sauerkraut, as it still is today. The fact that in Bavaria cabbage was eaten three to four times a day, as one sixteenth-century physician tells us, illustrates how important a foodstuff cabbage was for the common people. In the upper-class cookbooks, however, cabbage is rarely mentioned. Not only did it lack exclusivity, it was also thought to generate melancholy and cause nightmares. Its one redeeming feature was that it was considered an antidote to drunkenness. Cabbage juice with honey was recommended for people who had lost their voice, and cabbage leaves were used to dress wounds."

Now I’m confused. One is saying that in Medieval Europe the cabbage head as we know it had not yet been developed, the other is saying that certain cultures did have cabbage in head form. Although Food in Medieval Times was printed before the Cloisters article (2004) all of the sources listed on the article are much older (the newest is 1999.)

There is a good chance that the problem is in the huge timeframe covered by the term “Middle Ages” and in the large geography covered when one says “Europe” so they could both be right! Now I want to know: when and where is the earliest documented head of cabbage? When can we safely say that most of Europe had some form of cabbage that formed into a tight head? And which came first, cauliflower or broccoli?