When Science is Considered the Facts Remain.
Last month I explained some of the science behind creating an effective windbreak and why one of the most popular species planted for windbreaks/hedges in the southern highlands is not a good choice when the science is considered.
This article prompted community interest with the result being a discussion an ABC Radio Illawarra on the use of Leylandii (X Cupressocyparis leylandii) as windbreaks and hedges. During this discussion I described Leylandii as a garden thug that is totally inappropriate for planting as a windbreak or hedge and is a threatening species to our lifestyles and the environment.
Over the years the use of Leylandii as a landscape plant has been popular and controversial. Developed in England, Leylandii is a
hybrid cross originating from two coniferous species Cupressus macrocarpa and Callitropsis nootkatensis. It is a quick growing and shallow rooted, hardy tree capable of growing in excess of 40 metres high by 8 metres wide. Widely planted in England it has developed its reputation as a garden thug, creating conflict and division within the community.
In rural situations Leylandii grows as a dense wall that does not create an effective windbreak. Growing up to 40 metres it also casts heavy shadows that limits pasture or crop growth as well as potentially depriving neighbours of solar access and scenic views. When planted adjacent to our roads they can create ice patches on roads for excessive periods making some of our narrow, windy roads dangerous. Their foliage is highly combustible increasing fire risks in fire prone areas. In other parts of the world that have hot dry summers Leylandii are short lived as their shallow root system makes them susceptible to a disease called canker (Seiridium cardinal) that can ultimately kill the tree. Having to replace windbreaks due to fire or disease every 15 to 30 years is costly and unsustainable.
In urban situations Leylandii can be an effective quick growing hedge if pruned regularly. Left unpruned Leylandii is totally inappropriate as its mature size can deprive owners and neighbours of solar access increasing heating and lighting costs. Interference to TV or mobile phone reception could also be expected. Damage to underground services such a water and sewer mains is also a risk. Pruning required to manage these trees can be costly or time consuming with the eventual result being many hedges are left unpruned, leading to neighbourhood conflicts and possible legal litigation.
The excessive use of Leylandii in our Shire will result in a loss of historic and cultural landscapes and present further risks to our already threatened natural environment. Planting lines of Leylandii adjacent to our natural landscapes can be a threatening process by depriving them of light, water and nutrients. Many of the ecological communities in our shire are classified as endangered and the planting of threatening species adjacent to or within these communities could be considered a threatening process when put under scrutiny using scientific fact and rigor. Undertaking any process that threatens an endangered ecological community without a permit is a criminal offence.
As yet our local shire council does not list the Leylandii as an environmental weed. Maybe it is time our councillors reconsider its status using science rather than myth, ignorance or prejudice.
Many other plants widely planted in our landscape also threaten our natural environment even though Wingecarribee Shire Council has listed them as environmental weeds. Cherry laurel, agapanthus, Cootamundra Wattle, Silver Poplar, Cotoneaster, Perriwinkle, and African Daisy are classic examples. The planting of environmental weeds within or adjacent to endangered ecological communities could be considered a criminal act when natural science and existing legislation is combined. Think carefully and act responsibly before planting.
Much of our natural roadside vegetation has been identified as being significant and under threat. These vegetation corridors link fragmented ecosystems and do not benefit from planting threating plants adjacent to them. Our resources should be used to enhance our natural environment, not deplete it.
A list of environmental weeds in your shire can be obtained from your local council (www.wsc.nsw.gov.au/uploads/786/envweed_2007_brochure.pdf) or from environmentally conscious nurseries.