“Oh The Holly and The Ivy…”

What two plants capture the spirit of winter better than the classic pairing of Holly and Ivy?
They seem to be everywhere at this time of year—on cards, wreaths and in our carols — but these two heroes of the woods are far more than just winter decoration. They provide huge value to our woodland wildlife all year round!

The deep green prickly tangled foliage of Holly (Ilex aquifolium) and the dense twining creeping Common Ivy (Hedera helix) define the winter woodland landscape. You don’t need to travel very far to find these two in Fox Hill woods. They both provide shelter and protection to small birds, mammals and insects all year round. The Ivy flowers later in the summer into autumn, providing end of season nectar for bees,wasps and butterflies before they hibernate.
Alongside the Holly’s familiar red berries, Ivy’s black berries can normally be hard to spot, but together they provide important winter sustenance for birds when other plants are shut down and bare. This year there is a very impressive ivy bush absolutely loaded with black berries just at the start of the path up from Dorset Way opposite Heron Park.

“When they are both full grown…”

But did you know that these two plants share a remarkable, biological trait: they are both heterophyllous, meaning they change their leaf form and structure as they age or in response to their environment. 

Look closely on a mature holly bush and you may well find two different sorts of leaf:

• Prickly Leaves: These spiky, defensive leaves are grown on the lower branches and on young plants to deter browsing herbivores like deer. This energy-intensive defense is critical where the plant is vulnerable.
• Smoother Leaves: On the upper canopy of mature trees, where the leaves are safely out of reach, holly produces smooth-edged, spineless foliage. By switching to this less-defensive, simpler structure, the plant conserves the energy needed for reproduction.

On established ivy growing up a tree or wall you will also see two sorts of leaves: 

• Lobed Leaves: On the younger climbing shoots you will see the familiar deeply lobed leaves.  In this phase, ivy focuses solely on climbing towards the light and does not flower or fruit.
• Smooth almost diamond shaped-leaves: Once the plant reaches sufficient light, it transforms. It develops stiff, shrubby branches, and its leaves become smooth and unlobed. Only this adult form can produce the critical late-season flowers and fruit.

So, this December, as you admire the festive decorations, take a moment to appreciate the true ecological gift these plants are to our woods. The ecological strategies of holly and ivy with their leaf adaptations, late flowers and following late fruit make them indispensable to the health and survival of the woodland ecosystem. Perhaps we should change the last line of the carol…

“Of all the trees that are in the wood the Holly and Ivy share the crown!”