Incredible ivy has climbed in my estimation

IVY is an extraordinary plant. I was in a mixed-species wood the other day and I started to notice how selective it is about the species of tree it chooses to climb. In this wood its favourite was ash and its least favourite was holly.

The reason for this is pretty obvious. Ash is the last native Irish tree to get its leaves in the spring and one of the first to lose them in the autumn. Plants in a wood are engaged in a ceaseless battle for light so by selecting out ash trees to climb the evergreen ivy gets the maximum number of weeks in the year for uninterrupted photosynthesis.

Holly, on the other hand, is also evergreen and tends to have very dense foliage which doesn’t suit the ivy at all. In between these two extremes there seem to be grades of preference based on a mathematical equation that balances foliage density with the number of weeks in the year that the leaves are on the tree.