"The vine, though not native to Britain, is an important motive in British Bronze Age art…" says Robert Graves in 'The White Goddess', "… they will have used the bramble as a substitute". Possible, but Celts were living elsewhere too, e.g. in Burgundy, where the great Vercingetorix took his final stand against the Roman oppressor.
I think I can safely presume they knew the grapevine there…
Sacred to a lot of wine-loving gods (amongst whom Osiris and Dionysus), the vine stands for joy, exhilaration and wrath. Who freely partakes in the Mysteries of the Grape will release all inhibitions, speak the Divine Thruth and wake up with a Divine Hangover.
The vine is also the Weaver, linking other plants together with its runners, thus symbolic of the importance of respecting other people's actions and opinions.

The mythological figure for this month is beautiful Branwen, the sister of Bran. It is to avenge the ill treatment she suffered from her husband Mathowch, that Bran invaded Ireland. Branwen "Fair Bosom" was the Welsh goddess of the sea, of love and of sexuality, a Celtic equivalent to Venus and Aphrodite.

The mystical white swan figures in several Celtic tales. It is a symbol both of Sun and the Moon, of Light, of intuition and gracefulness, of spiritual evolution. Their feathers were used in the ritual cloaks of the Bards. Stories also exist about swans shedding their feathers and thus turning into maidens.

The Ogham sign attributed to this month is Muin.