Managing aerial root attachment in ivy species
Faye Thomsit-Ireland1, Tijana Blanuša2, Emmanuel Essah1 and Paul Hadley1
1
University of Reading
2
Royal Horticultural Society
Executive summary
Self-clinging climbing plants such as Hedera helix and H. hibernica (common ivy and Irish ivy), can be
used for façade greening around buildings. Façade greening can insulate the building exterior against
weather extremes thus reducing the need for winter heating and summer cooling. Ivy use around
buildings is anecdotally associated with damage to walls, gutters and windows, and difficulty in
controlling ivy attachment. This deters some property owners from using ivy.
Experiments were designed to explore altering wall conditions to reduce ivy attachment. In the
laboratory, a model system was used. Treated cork panels were positioned to create attachment in
ivy cuttings and determine the effect of two anti-graffiti paints, copper and zinc sheets versus the
untreated control. The experiment was repeated outdoors with established ivy plants, the
treatments were anti-graffiti paint, copper mesh and an untreated control. In both experiments the
metals, and silane based anti-graffiti paint prevented aerial root attachment in the cuttings and
established ivy. In a basic cost analysis, the silane based anti-graffiti paint was the least intrusive and
cheapest option for ivy aerial root management.
Introduction
Many processes involved in the attachment of ivy aerial roots have been studied. These include the
mechanism and stages of attachment (Melzer et al., 2010), and strength of attachment to surfaces
(Melzer et al., 2012). Preventing ivy aerial root attachment has not yet been sufficiently studied.
While the phytotoxic effects of copper and zinc have been explored for “true” roots, the techniques
and materials could work with aerial roots as well. Both zinc sheets and copper meshes/sheets can
be attached to building walls and the model ’walls’, thus were trialled in the outdoor and indoor
experiments. Anti-graffiti paints have suitable properties for preventing attachment, such as water
and oil repulsion so they were included in the experiments. Two experiments were created, a model
laboratory system with cuttings growing next to ‘walls’ and an outdoor experiment on a building wall
where treated cork panels were placed next to established ivy.
Materials and Methods
The laboratory experiment used excised shoots from one year old Hedera hibernica plants and two
year old H. helix plants. The excised shoots were grown in close proximity to 10 cm x 10 cm cork
panels treated with a silane-based anti-graffiti paint ‘Easy –On’, a polyurethane based anti-graffiti
paint ‘Pegagraff® hydro’, copper sheet, zinc sheet, and the untreated control. The cuttings were
attached to the ‘walls’ to encourage a thigmotrophic response which contributes to the production
of aerial roots (Negbi et al., 1982). Baseline measurements (stem diameter, leaf number, and aerial
roots) were made to assess all the cuttings were similar. At the end of the experiment stem length,
weight, leaf number, total attachment length, and detachment force were measured.
The outdoor experiment used a group of pruned H. helix ‘Glacier’ plants, established since 2008,
growing up a brick wall. At the start of the experiment, three model ‘walls’ were constructed with six
24 x 30 cm treated cork panels. The treatments were ‘Easy –On’, copper mesh #60, and untreated
control. At the end of the experiment the maximum detachment force, shoot length, weight (total
shoot, aerial root, and leaf), stem diameter (two measurements made at the middle of the stem) and
aerial root attachment length were measured.
Results
Within the laboratory experiment, the growth measurements were significantly different between
the species however, not within the species, so the species were analysed separately. Across
treatments for H. helix, the average initial stem diameter was 1.57 mm, leaf number 3, and aerial
root number 28. The average initial stem diameter across treatments for H. helix was ≈ 39% smaller
than H. hibernica. There were initially 50% more leaves and over three times more aerial roots in H.
helix than H. hibernica. During the experiment there was no significant difference in growth between
treatments within each species. In the laboratory and the outdoor experiment, similar results were
found in terms of the attachment. Copper completely prevented attachment and ‘Easy on’ was not
significantly different to copper in detachment force per length of attachment. The detachment force
for the control (and Pegagraff in the laboratory experiment) was at least 500% more than ‘Easy on’.
Conclusion
In the laboratory and outdoor experiments, zinc and copper sheets/mesh, and the silane-based antigraffiti paint prevented or severely weakened ivy’s attachment to cork. The ivy strongly attached to
the cork when it was not treated. While cork is not a true replica of a brick and mortar wall, these
treatments may be used on buildings. This work has highlighted some low maintenance options for
ivy control and management on buildings, and mechanisms to reduce the chance of ivy creeping into
gutters or windows. From the cost comparison (data not shown), the silane-based anti-graffiti paint
was the cheapest solution and has the least visual impact on the building. As ‘Easy on’ was a clear
paint it would be a discrete deterrent and providing there were no adverse effects to the building,
this would be the treatment to be investigated further. The next stage of this work attempts to
reduce the dominant juvenile climbing stage of ivy by controlling the growth further, and encourage
mature shrubby growth. This is being investigated using ledges covered in the attachment inhibitors
to establish whether a permanent barrier to ivy attachment can be generated.
Acknowledgements
I would like to thank my sponsors, the Royal Horticultural Society (RHS), Sutton Griffin Architects and
the Engineering and Physical Sciences Research Council (ESPRC), along with the technicians at the
glasshouses.
References
Melzer, B., Seidel, R., Steinbrecher, T. & Speck, T. (2012). Structure, Attachment Properties, and
Ecological Importance of the Attachment System of English Ivy (Hedera helix). Journal of
experimental botany, 63, 191-201.
Melzer, B., Steinbrecher, T., Seidel, R., Kraft, O., Schwaiger, R. & Speck, T. (2010). The Attachment
Strategy of English Ivy: A Complex Mechanism Acting on Several Hierarchical Levels. Journal
of the Royal Society Interface, 7, 1383-9.
Negbi, M., Zamski, E. & Ze'Evi, O. (1982). Photo- and Thigmomorphogenetic Control of the
Attachment of the Ivy (Hedera helix L.) to its Support. Zeitschrift für Pflanzenphysiologie, 108,
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