In the past few weeks, the Derry Walls have become green with vegetation. Most abundant is ivy-leaved toadflax Cymbalaria muralis.
This plant, native to the Southern Europe, is common on ancient walls and is also called Wandering Sailor and Coliseum Ivy. It has heart-shaped leaves with three or more lobes. The delicate flowers are held on stalks which are phototrophic: positively when flowering and negatively when the seeds are produced. This results in the seeds being deposited in crevices in the Walls when the stalks start to turn away from the light. Another plant common on the Derry Walls is Walls Rue Asplenium ruta-muraria, a species of fern which love the lime-mortar used to point the Walls.
Another plant to look out for on the Walls is Pellitory of the Wall Parietaria judaica. It bears tiny flowers directly on its hairy stems. It overwinters through buds located just below the soil surface.
The DOE Conservation Plan for the Derry Walls, policy 41 states “guidance should be included in the Management Plan that will ensure existing botanical interests are identified, managed and protected in an appropriate manner”. However the DOE Management Plan’s only mention of botany is to state that the NIEA will remove weeds from the Walls on an annual basis. Certainly, plants which are deep rooting such as buddleia cause damage to the structure of the monument. Small annual plants can help the monument by shading the masonry and supporting a more diverse range of wildlife. The Friends of the Derry Walls will be encouraging DOE NIEA to produce specific guidance on the management of plant life on the Derry Walls, controlling those which injurious, protecting those which add to the attractiveness of the Walls for visitors and wildlife. A walk around the walls with a botanist will be arranged – details to come.