It was only when I looked up the lyrics of this well known carol, that I realised that despite top billing in the title, ivy doesn’t get a mention past the first line. I had been trying to remember what ivy attributes were mentioned and could only remember the white blossom, red berry and prickle of the holly, (bitter bark is also involved but maybe because I have never tasted it, this didn’t spring to mind).
Both of these plants change their leaf shape as the plant matures. Holly often becomes less spiny higher up the tree when away from grazing predators, but ivy changes quite dramatically from juvenile shoots bearing palmately lobed leaves, alternately arranged, which climb using hairy adhesive rootlets, to the mature ‘arborescent’ form. As a consequence of differential DNA replication, when ivy is about to flower the new leaves become smooth margined and spirally arranged. (For a detailed description see Daniel J. Metcalfe’s paper in the 2005 Journal of Ecology, on Hedera helix). This ‘tree ivy’ retains its shrubby character when propagated from cuttings.
But what is this phenomenon is called? Internet research drew a blank. I took at break while working in the library at Wisley and searched through all the monographs on both types of plant and found nothing. Even Colin Crosbie, curator at Wisley gardens, couldn’t put a name to this change. He suggested that Alan Mitchell might have coined a term for it in one of his books, but no luck.
What I did find out was where the Ivy went. In Jane Fearnley-Whittingstall’s book on Ivies she quotes the lines;
Ivy hath berys as black as any slo
There came the owle and ete him as she go
This has the rhythm of the song we now sing and it comes from the carol “The Contest of the Ivy and the Holly” These words may have a pagan origin in which the male is symbolised by the holly and the female by the ivy, which may have inspired the tradition of women and men alternating the verses of this song. Sir Walford Davies arranged the setting of the traditional tune that we use today.
There are two National Plant Collections of Ilex, one at RHS Rosemoor and the other held by Mr & Mrs Barnes in Pembrokeshire. In October, Christine Walkden of Gardener’s Question Time visited this Welsh collection and at the time of writing this post you can listen to this programme on this link. Hedera National Collections can be found at Fibrex nurseries in Warwickshire and at Erdigg Hall Gardens in Wrexham.