Analysis of information sources in references of the Wikipedia article "Sir Gawain and the Green Knight" in English language version.
...the Green Knight, alias Bertilak, is an immensely vital person who is closely associated with the life of nature: his greenness, the birds and flies of his decorative embroidery, his beard as great as a bush, the holly branch in his hand, the energy he displays as a huntsman-all give him kinship with the physical world outside the castle.