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The Ecosystem Benefits of managing
the invasive non–native plant
Rhododendron ponticum in
Snowdonia
Snowdonia Rhododendron Partnership
2015
Rhododendron in Snowdonia
A plant native to areas of the middle-east and Mediterranean countries, it is thought that
Rhododendron ponticum was first introduced to the UK as an ornamental plant during the in
1763 (Cross, 1975). However, it soon became established in the wild, with the rate of spread
accelerating in the latter half of the 20th century. This is possibly as a result of changes in land
use, increased grazing pressures and a reduction in rabbit populations as a result of
myxomatosis. It has been suggested by some that the plants spread has become stable, although
it remains an aggressive plant in certain areas and on certain habitats.
As to why certain areas are affected worse than others, the reasons aren’t entirely clear.
However, genetic analysis of Rhododendron suggests that British populations often contain the
genes of Rhododendron catawbiense, a North American species, which may confer greater cold
tolerance and therefore allow it to colonize colder parts of Britain. However, it is not known if
this applies to Rhododendron in Snowdonia.
Why we wish to eradicate Rhododendron ponticum
Whilst it may be difficult to argue against the aesthetic attractiveness of the plant when it’s in
bloom, the negative impacts of Rhododendron far outweigh the positive aspects of its presence.
Invasive species have been identified as one of the major drivers of ecosystem degradation in
Wales (UK National Ecosystems Assessment, 2011), and cost the Welsh economy approximately
£7 billion per annum (National Assembly for Wales, 2013). Furthermore, invasive non-native
species (INNS) are listed as the second biggest threat to native wildlife globally after habitat
loss. Whilst it’s impossible to break the cost/threat posed to individual species and/or areas,
much of this cost derives from the impacts of INNS on the ability of natural ecosystems to
function properly, resulting in degradation to key ecosystem services.
Due to its ability to out-compete, smother or shade native species, it has had severe detrimental
impacts to many of our natural
habitats. By now, it is widely
regarded as one of the main
invasive non-native species
(INNS) present in north-west
Wales, with an estimated area
of over 2,000 ha now infested
by Rhododendron within the
National Park (SNPA, 2008).
Area behind Beddgelert which has been cleared of Rhododendron ponticum (2014)
What are ecosystems and ecosystem services?
An ecosystem can be defined as a community of living organisms (biotic factors), which in
conjunction with the physical environment (abiotic factors), function together in a given area of
the environment. The benefits that humans derive from ecosystems are often referred to as
ecosystem services. These can range significantly, but can be grouped into four broad
categories; provisioning, regulating, cultural and supporting services (Millennium Ecosystem
Assessment, 2005). They are defined as follows:

Provisioning services are the products obtained from ecosystems. In Snowdonia, these
would be such things as food, timber and peat;

Regulating services are the benefits obtained from the regulation of ecosystem
processes, such as regulation of climate, water, pest and diseases;

Cultural services are the non-material benefits people obtain from ecosystems through
recreation and aesthetic pleasure;

Supporting services are ecosystem services that are necessary for the production of all
other ecosystem services. Examples include biomass production, nutrient and water
cycling, and the conservation of natural habitats.
Annex I shows the level of impact Rhododendron infestation has on a wide variety of
ecosystems services in Snowdonia. Some of the key impacts include:

Soil quality – it has long been said that Rhododendron ponticum has adverse impacts on
soil health, a key ecosystem service. These include increased soil acidity and a decrease
in biodiversity essential for maintaining soil health e.g. earth worms (UK National
Ecosystems Assessment, 2011).

Pollination – species such as heather provide a valuable source of food for our native
pollinator species. By decreasing the availability of food sources to pollinators,
populations will decrease, as has been witnessed in recent years. Indeed, according to
the Welsh Government, habitat loss is one of the main reasons for the decline in native
pollinators in Wales (The Action Plan for Pollinators in Wales, 2013);

Disease and pests – whilst Rhododendron itself can be considered a pest, its ability to
host other diseases and pathogens such as Phytophora, thus facilitating their movement
in the wider landscape, is of great concern. Such pathogens pose a threat to both native
and commercial woodlands, both of which are vitally important in terms of their
ecological and commercial values in Snowdonia;

Primary productivity – this includes food production (both livestock and crops), timber
production and wild fish stocks, all of which are essential in supporting the local
economy in Snowdonia. Due to its highly invasive nature, Rhododendron infestation will
make otherwise suitable habitats unsuitable for grazing animals, thus reducing the
amount of land available to farm.
As we all know, Snowdonia is blessed with a rich diversity of habitats, which in turn support a
rich array of plants and animals. Collectively, they are referred to as biodiversity, and include
everything from the tiny micro organisms found in soils and waters to large plants and all the
creatures which call Snowdonia their home. Basically, it’s all living things!
As a non-native invasive plant, Rhododendron ponticum would not have grown naturally in
Snowdonia had humans not introduced it. As mentioned above, its infestation can have dramatic
impacts on the native habitats of Snowdonia, primarily habitats of the uplands (moorlands and
heath), our native woodlands, unimproved or semi-improved species rich grasslands and
freshwater habitats. Specific impacts on each key habitat are discussed below.
Moorlands and Heath
Snowdonia National Park and the surrounding regions are defined by upland habitats, where
both moorland and heathland is widespread in areas such as the Migneint, the Berwyn
Mountains and Mynydd Hiraethog, all of which are protected under either national or European
law due to their ecological importance. Whilst the majority of these habitats are to be found in
upland areas, they can also be found on hillsides between enclosed farmland and the open
mountain (often referred to as Ffridd in Wales), and even in lowland areas such as Arthog Bog
on the Mawddach Estuary. Such habitats provide a wide and diverse range of ecosystem
services, as listed in Figure 1.
Rhododendron encroachment into upland habitats can have drastic impacts on the ecosystem
services we derive from them. Whilst altitude is thought to be a limiting factor in the spread of
Rhododendron into upland areas (very few bushes have been recorded above 400m), its ability
to withstand wide climatic variation and a tolerance to a range of substrates means it can grow
almost anywhere where there is sufficient moisture (Snowdonia National Park, 2008).
Due to its ability to withstand a wide range of environmental conditions, Rhododendrons is able
to outcompete many native plants, having knock-on impacts on associated fauna and resulting
in decreased ecosystem functioning. The dense shade produced by Rhododendron canopies
leaves little light penetrating through, thus associated flora, even shade-loving bryophytes, or
their associated fauna, are minimal. Furthermore, studies show that few species of invertebrates
utilise Rhododendron as a food plant (Judd and Rotherham, 1992). Consequently there is little
to threaten rhododendron’s expansion and food chains based on Rhododendron are likely to
have low biodiversity value. Considering that biodiversity is widely regarded as a key
supporting service, essential for the healthy functioning of all other ecosystem services whether
they be provisioning, regulating or cultural, this can only be a bad thing.
An example of this would be Rhododendron encroaching into heath land, suppressing the
growth of native plants such as heather, thus diminishing a vital food source to local pollinator
populations. Another example would be the growth of Rhododendron on bogs and mire. If dense
stands are allowed to form, this will be to the detriment of bog forming mosses such as
sphagnum spp. These mosses provide a range of ecosystem services such as retaining and
filtering water, and peat formation. Furthermore, in abundance, Rhododendron growth could
essentially dry out wetlands, making the underlying peat more susceptible to oxidisation.
Ultimately, the carbon stored in peat would be released into the atmosphere, contributing to
global warming rather than helping to mitigate it.
As alluded to above, the uplands define Snowdonia as we know it. Indeed, it’s this diversity of
landscapes and their ever changing colours throughout the seasons that attracts millions of
visitors to the area each year. This makes tourism one of the main economic drivers in
Snowdonia. It is difficult to believe that anyone would welcome a change from the diverse
tapestry of native habitats we have in our landscape to one dominated by Rhododendron.
Whilst some might argue that Rhododendron in bloom is itself a site worth seeing, it’s important
to remember that the plant flowers for only a short time period, and that for the rest of the year
it provides nothing but a monotonous green carpet on what would otherwise be a varied and
colourful landscape, changing throughout the seasons.
Along with grasslands, heathlands are one of the richest habitats in respect of flowering plants
and of the 472 species found there, around one in four are threatened (State of Nature Report,
2013). Many of the species are often locally distinctive, thus their genetic make-up could differ
drastically to other areas of the UK. The maintenance of genetic diversity is critical in view of the
increased threat from climate change, and is needed in order to facilitate successful restoration
and conservation projects (National Ecosystem Assessment, 2011).
Service
Peat
Description
Meat from grazing animals (primarily sheep and some beef cattle in
Snowdonia) and fibre (wool)
Upland soils are amongst the most carbon rich in the world
Wild game
Traditionally, large areas of the uplands were managed for wild game
Genetic resources
Heathland are amongst some of the most species rich habitats
Energy
From hydro-electric and wind energy power schemes
Water
Over 80% of our water supplies comes from upland areas
Pollination
Heathland amongst most diverse habitats in terms of flowering plants
Water quality
Moss rich bogs act as a natural water filter
Upland habitats have the ability to store large amounts of water, thus
reducing risk of flood and providing a steady source during times of
drought
By conserving carbon rich soils and carbon sequestration potential
Livestock
Water regulation
Climate control
Disease regulation
Regulation of
pollutants
Cultural heritage
Human well-being
By hosting such pathogens as phytophthora and ticks (lime disease)
Intercept both water borne and air borne pollutants and pH buffering
The uplands define Snowdonia as we know it a historical landscape
with archaeological features that are degraded/damaged by
rhododendron
Derived from being outdoors (both mental and physical)
Tourism and recreation Varied landscape of Snowdonia attracts millions of visitor annually
Education
Upland habitats provide a range of education opportunities
Biodiversity
Required for the maintenance of healthy ecosystems
Soil formation, nutrient
and water cycling,
oxygen production
Forests facilitate all these things, essential for the maintenance of
healthy ecosystems and indeed, life itself
Figure 1. Main ecosystem services derived from upland habitats
The main benefits derived from controlling Rhododendron ponticum on moorlands and heath
lands in Snowdonia are:


Increasing the area of native flora for the benefit of biodiversity, including pollinator
species, within the National Park;
Decreasing the risk of spread of pests and diseases in the wider environment;



Ensuring that wetlands such as blanket bogs remain in favourable condition and thus
continue to provide associated ecosystem services in relation to water retention and
quality;
Bringing land back into agricultural production;
Improving access to the countryside to the public and making the area more
aesthetically pleasing.
Woodlands
Snowdonia is renowned for its vast variety of woodlands, from the ecologically rich Atlantic oak
woods of Meirionydd, full of mosses, liverworts and lichens, the mixed ash woods of the Nant
Gwynant valley and areas of wet woodland dotted around the Park. As with heaths and bogs,
many of these are designated due to their high conservation value. It is also worth remembering
that it isn’t only our native woodlands that are under threat from Rhododendron, but also
commercially planted coniferous crops such as those found at Gwydir Forest, Coed-y-Brenin
and the Dyfi Forest.
It is fair to say that the relationship between Rhododendron and woodlands is not a good one.
Due its ability to produce a dense canopy layer and grow in well shaded areas, Rhododendron
will more than likely out-compete the natural regeneration of trees in woodlands, particularly
lower plants such as bryophytes and lichens. If left untreated, the Rhododendron bushes will
eventually form a thick blanket in the under storey, and as mature trees die, the woodlands will
ultimately be replaced. This is a particular problem amongst light demanding tree species, such
as oaks and birches. Unfortunately, it is not entirely clear what the full impacts of
Rhododendron are on the natural cycle of woodland regeneration due to no such studies being
taken (as far as we’re aware). This is primarily due to the length of time it takes for a
Rhododendron stand to mature and then die back. Whilst it may be the case that stands will
eventually die back and offer opportunities for native species to re-colonise, the longevity of
Rhododendron means that such benefits would not be observed for centuries, and the shorter
term damage far outweighs any potential opportunities for re-generation in the future.
It is not only the above ground organisms that suffer as a result of Rhododendron infestation.
For example, mycorrhizas, which are a community of soil fungi that form symbiotic (mutually
beneficial) relationships with the roots of plants, will decrease in line with reduced diversity of
plant species. Whilst some mycorrhiza form beneficial relationships with Rhododendron (thus
facilitating its growth) others are adversely impacted, especially those associated with native
woodlands. Consequently, woodland ecosystems that are dependent on these unique
relationships between native trees and mycorrhizas for healthy functioning suffer and therefore
any threat to this vital relationship is potentially critical.
Rhododendron ponticum is also known to host pathogens
such as Phytophthora ramorum (DEFRA), a pathogen
which is a great threat to conifers, notably larch and to our
native broadleaf woodlands and to heathland species i.e.
bilberry (Vaccinium myrtillus). As a host, Rhododendron is
likely to facilitate the spread of such pests in the wider
countryside.
Unfortunately, Phytophthora does not
seriously
threaten
Rhododendron’s
survival.
Consequently, its elimination will dispose of one of the
major pathways for the spread of Phythophora and other
diseases. In view of the increased threat posed from such
diseases as a result of climate change (Ray, 2008),
reducing potential pathways now is essential in order to
conserve ecosystems over the coming decades.
Furthermore, it may produce biochemicals which can
affect other plants, inhibiting the germination or seedling establishment of other species.
Rhododendron infestation in non-native commercial forestry plantations can also be highly
problematic when it comes to harvesting those crops. This is primarily due to issues relating to
access, as treatment of Rhododendron becomes increasingly difficult within dense woodland.
This will ultimately push up the cost of felling timber, sometimes adding tens of thousands to
forest operations. This has been witnessed firsthand here in Snowdonia in areas such as Coed yr
Eryr in Nant Gwynant. Rhododendron also makes the replanting or regeneration of these
plantations almost impossible as the stumps which are left behind are a huge issue in terms of
restricting access. Without whole stump removal, planting by both machine or by hand would
become very difficult, and the costs associated with such operations would increase
dramatically.
Service
Timber
Genetic resources
Water
Crops and livestock
Water quantity
Air quality
Description
Both native woodlands and forest plantations are important sources of
timber, used for a variety of purposes i.e. fuel, construction, pulp etc..
Having healthy, mixed species woodlands provides local genetic
variability including the genetic resource of the component biota.
Heavily wooded catchments often provide water to wider communities
and improving water quality.
Woodlands sometimes facilitate livestock (agro-forestry) and provide
non-timber products such as berries, honey, fungi and meat i.e. venison
Woodlands also provide shelter and forage for livestock.
Regulating flood control by reducing the flow rate of water into the lower
catchment during prolonged periods of rain; by creating a complex
structure, woodland slow the passage of water to the rivers, aiding
infiltration and ameliorating flooding . (McIntyre et al, 2008)
Trees produce oxygen, which is essential for life on earth, and capture
atmospheric pollutants
Soil quality
Can stabilise and thus protect soil from erosion
Pollination
Provide habitat for diverse wild pollinator communities
Associated fauna i.e. bats can help regulate the incidence and spread of
insect pests
By sequestering carbon (in soils and in the timber itself)
Diseases and pests
Climate control
Provide localised shelter to wild and domestic livestock during extreme
weather
Environmental
setting
Providing, amongst others things, an educational resource, recreational
opportunities and a sense of place
Biodiversity
Maintain a wild and diverse range of wildlife, often locally distinctive and
adapted to those areas
Soil formation,
nutrient and water
cycling, oxygen
production
Forests facilitate all these things, essential for the maintenance of healthy
ecosystems and indeed, life itself
Figure 2. Ecosystem services derived from the woodlands in Snowdonia
The main benefits derived from controlling Rhododendron ponticum in the woodlands of
Snowdonia include:






Improve the diversity of flora associated with native woodlands in Snowdonia;
Allow for forest operations such as felling to be undertaken more efficiently, thus
reducing costs;
Reduce the risk of spread of pests and diseases within woodlands (both native and
plantations);
Make for healthier and more resilient woodland ecosystems which in turn offer local
genetic variability;
Improve soil quality and decrease soil erosion;
Increase recreational opportunities within woodlands.
Semi-natural or unimproved grasslands
Semi-natural or unimproved grasslands are usually species rich when compared with areas of
improved grassland. Although not abundant in Snowdonia, those that are left offer a unique
habitat, not only rich in plant diversity, but also supporting an array of fungi and invertebrate
species. Furthermore, they provide valuable grazing land for livestock, which is required to
manage the encroachment of scrub and maintain the species rich vegetation found in these
habitats. Services provided by semi-natural and improved grasslands can be found in Figure 3.
Species rich grasslands have declined dramatically over the last few decades, with an estimated
97% loss in such habitats in the last 50 years (Check: David Stevens for Wales data)Pywell et al.,
2002). Whilst such habitats aren’t abundant in Snowdonia (owing primarily to the topography
of north-west Wales), it is vital that those remaining fragments are conserved due to their
scarcity. Whilst INNS has not traditionally been one of the main drivers in the decline of seminatural grasslands in the UK, it could pose an increased threat to these habitats in future years
should they go untreated (UK National Ecosystems Assessment, 2011).
Many of the impacts Rhododendron has on species rich grassland habitats are similar to those
associated with other habitats discussed previously. That is, due its ability to outcompete
natural vegetation associated with unimproved or semi-improved grasslands, Rhododendron
will eventually replace native species and compromise the ecosystems services they serve.
For example, Rhododendron encroachment into unimproved grasslands will essentially exclude
livestock (due to the density of the bushes), rendering them unsuitable for grazing livestock.
Furthermore, Rhododendron itself is also poisonous to cattle and sheep (Cooper and Johnson,
1984). Consequently, if left to spread, that
piece of land will essentially become
unproductive. This then leads to the loss
of species diversity, which will impact on
local populations of pollinators and so
on.... in addition, the loss of productive
land will lead to reduced agricultural
subsidies to farmers, which is obviously
never welcomed!
It is also worth mentioning the impacts of
Rhododendron on soil, as it is said that its
growth will have an acidifying impact in
areas in which it grows. However, there is
little scientific evidence out there to back
this up. What is perhaps a little more
apparent is the impact Rhododendrons
can have on earthworms, essential for the
maintenance of healthy soil. Although
unimproved or semi-improved grasslands
can be found on a range of soils
(calcareous, neutral or acidic), they are
often fairly productive free-draining soils
compared to those found in higher altitudes. Earthworms are an essential part of maintaining
healthy soil, and are also a vital food source to other species, primarily birds and small rodents.
Consequently, a decrease in populations could have dramatic impacts on local food chains and
soil health.
Service
Livestock
Genetic
resources
Biomass
Pollination
Climate
Water
Description
Semi improved or unimproved grasslands require appropriate grazing to
eliminate invasive weeds and maintain diversity, thus providing food (meat,
milk) and fibre (wool)
Less intensively managed grasslands are far more species rich than those
which have been improved, thus they maintain a higher level of genetic
resources
For silage or crops
Less intensively managed grasslands are far more species rich than those
which have been improved
Grassland soils are a reserve of carbon and other greenhouse gases
Increased vegetation cover will reduce surface water run-off , providing flood
protection, and storing pollutants, particularly in riparian areas
Environmental
settings
Protecting valued species and agricultural heritage and providing areas for
recreational activities i.e. walking and educational visits
Biodiversity
Required for the maintenance of healthy ecosystems
Figure 3. Ecosystem services derived from semi-improved or unimproved grassland habitats
The main benefits derived from controlling Rhododendron ponticum within the grasslands of
Snowdonia are:



Reinstating land which was previously unsuitable for grazing back into agricultural
production, primarily grazing and arable to a smaller extent;
Decrease the risk of illness/fatalities within livestock as a result of the ingestion of
Rhododendron litter;
Increase vegetation cover and therefore reduce surface run-off.
Freshwater habitats (lakes and rivers)
Whilst the threat of Rhododendron on freshwater habitats is perhaps less apparent than other
INNS such as Himalayan balsam (Impatiens glandulifera) and Japanese knotweed (Fallopia
japonica), it can nevertheless have severe harmful impacts these ecosystems.
Rhododendron will thrive in riparian areas, outcompeting native vegetation on river banks and
the shores of lakes and ponds. Whilst the loss of native vegetation in these areas will result in
many of the same impacts as in other habitats i.e. loss of food source to native pollinators, it can
also have additional adverse impacts in freshwater environments. For example, riparian
vegetation supports a diverse population of invertebrates, the main food source of some fish
species. Trout depend on invertebrates which live in riparian areas for up to 80% of their food
source. Rhododendron stands don’t support anywhere near the same level of invertebrates as
those of native vegetation, therefore decreasing the food source to fish populations significantly.
the lack of understorey associated with a stand of Rhododendron leaves soil bare and thus
susceptible to erosion during periods of heavy rain. Whilst this is true in other habitats, it’s
more of a problem on streams and rivers where the force of the water is able to erode far
quicker than surface run-off in fields or woodlands.
Erosion can have adverse impacts on water quality which in turn, impacts on local fish
populations. Often, such soils are rich in metals, and increased flow can wash such undesirable
elements into watercourses, altering the pH and chemical composition of freshwater habitats
and having significant adverse impact on local fish populations.
Furthermore, large scale erosion can also often lead to significant loss of land which would
otherwise be suitable for farming. This is particularly problematic along larger rivers and
during flash flooding events. The water that we use to drink and wash in comes from freshwater
habitats via reservoirs and water treatments works. The cleaner the water is reaching these
works, the easier it is to treat and, more importantly perhaps, less expensive and less damaging
to the environment.
The accumulation of dead Rhododendron litter is especially problematic in standing water such
as ponds and the edges of lakes. Such habitats are often rich in flora and fauna, supporting wild
fish stocks, invertebrates and a range of freshwater flora. Rhododendron leaves are notoriously
slow at decomposing, thus they are able to accumulate on the surface of standing water, forming
a thick, impenetrable film. Many of the plants which are affected in such circumstances are
natural cleansers of water, thus further contributing to the worsening of water quality within a
catchment.
Whilst discussing freshwater habitats, mention must be made to other habitats that are perhaps
not freshwater habitats in their own rights, but have a strong link to our rivers, ponds and lakes.
These include such habitats as floodplain wetlands, marshlands and fenlands. The ecosystem
services derived from these habitats vary massively, but would include such things as providing
land for grazing, removal of pollutants, flood control and climate control (through the
conservation of carbon rich peaty soils). They can also impact on manmade structures
associated with freshwater habitats, such as culverts. As Rhododendron leaves decay far slower
than that of native species, they can often accumulate in culvers and small channels, leading to
blockage. If this happens on a larger scale, it can lead to localised flooding of roads for example.
Service
Description
Water
Lack of understorey can lead to increased levels of riverside erosion
Wild fish
In rivers, ponds and lakes
Farmed fish
Similar to wild fish
Peat
On adjacent habitats i.e. floodplains and bogs/marshes
Riparian habitat controls surface water run-off and reduces sedimentation
levels
Both river-flow and flood regulation
Natural freshwater systems support physical recreation. Mismanaged
freshwater habitats can be sources of water borne diseases and disease
vectors
Water quality
Water quantity
Human health
Environmental
setting
Tourism and
recreation
Biodiversity
Can provide a sense of place, defining specific landscapes
Attracting fishing enthusiasts, naturalists and outdoor recreationists
Support a diverse range of species essential for maintaining ecosystem health
i.e. spawning grounds
Figure 4. Ecosystem services derived from freshwater and associated riparian habitats
The main benefits derived from controlling the spread of Rhododendron ponticum on the
freshwater habitats of Snowdonia are:




Minimising the impact on riparian habitats and the flora and fauna they support;
Reduce the risk of contamination as a result of increased sedimentation;
Decrease soil erosion, which can impact on both water quality and lead to the loss of
agriculturally productive land.
Improve flood alleviation by slowing the flow of rainwater into catchments.
What we are doing
One of the main statutory purposes of all National Parks is to ‘conserve and enhance the natural
beauty, wildlife and cultural heritage’ of the area in which that respective National Park lies. The
spread of invasive non-native species poses a threat to all three of the above, as reflected by
Objective 5b of the Snowdonia National Park Management Plan 2010-15 (SNPA, 2010). This
states that the Authority will ‘continue efforts to reduce the land area covered by invasive
species’ within Snowdonia and its environs over the coming years. In order to achieve this
objective, Snowdonia National Park Authority have been working in partnership with other
relevant organisations, third sector nature groups and private landowners over the last decade
in treating vast areas blighted with Rhododendron infestation. Project partners include the
National Trust, Natural Resources Wales (previously the Countryside Council or Wales and
Forestry Commission Wales) and Gwynedd Council, as well as various volunteer groups.
Using local contractors, over 600ha of land has been treated to date (winter 2014), primarily
around the Nant Gwynant/Beddgelert area, the Ffestiniog Valley and along the Mawddach
Estuary. To put it into perspective,
that’s around the size of 560
standard
football
pitches!
Treatment involves three stages of
work – the primary phase of
clearance, and a secondary and
third phase to tackle re-growth.
These are usually undertaken 2
and 5 years after the initial work
respectively. Methods of control
are dependent on factors such as
accessibility, density and height,
but the most common are cutting
and then burning or chipping the
vegetation,
stem
injecting
individual plants with glyphosate
based chemicals or simply
spraying the leaves of the plant
using
standard
knapsack
equipment (usually used for
treating re-growth during the
second and third phase of work).
Further monitoring is undertaken
post treatment, usually five to 10
years after the third phase of work
is completed, to ensure recolonisation has not taken place.
What you can do
Almost all the Rhododendron which we now see growing in the natural environment originated
from gardens, where it is often planted as an ornamental plant, particularly since the post
Victorian era. Whilst the popularity of Rhododendron ponticum as an ornamental plant has
somewhat lessened in recent times, those plants which remain, unfortunately, still provide a
significant seed source into the wider environment. Consequently, if you have Rhododendron
bushes growing in your gardens, then we ask that you destroy those plants and replace them
with more appropriate species of tree or shrubs. Staff from the Conservation and Agriculture
department at Snowdonia National Park can provide free advice regarding suitable
management techniques and/or appropriate species for re-planting including other species or
hybrids of Rhododendron should it be required.
With continual support from relevant stakeholders, efforts to control the spread of
Rhododendron will persist, both complementing work already undertaken, and expanding into
areas that have so far been untreated. It is hoped that with adequate resources, continued
efforts and strategic implementation of work programmes, Snowdonia National Park can once
again be free of Rhododendron ponticum.
Conclusion
Rhododendron ponticum is a highly invasive non-native species that has had dramatic adverse
impacts on some of Snowdonia’s natural habitats. Its ability to out-compete natural vegetation
and dominate vast areas of the landscape alters the functioning of natural ecosystems and
degrades the quality of services they provide. Whilst it is acknowledged that further research
needs to be undertaken to measure the true extent of its impact on elements of the
environment, they are considered negative amongst experts in the field. With sustained
management and effective partnership working, successful eradication of Rhododendron
ponticum is possible, allowing for the recovery of affected habitats and associated services.
However, this will only be possible with both long-term and landscape scale management, and
with the support of sustainable funding streams.
Bibliography
Awdurdod Parc Cenedlaethol Eryri (2008). Rhododendron in Snowdonia and a strategy for its
control. Snowdonia National Park Authority, Penrhyndeudraeth.
Cooper, M R & Johnson, A W (1984). Poisonous Plants in Britain and their effects on Animals and
Man. MAFF Reference Book 161. HMSO, London.
Cross, J.R. (1975). Biological Flora of the British Isles; Rhododendron ponticum L. Journal of
Ecology, Vol 63, No 1. British Ecological Society. London.
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Annex I
Service
Group
Ecosystem Service
Mountains,
Moorlands
and Heath
(lakes and rivers)
High
Moderate
N/A
Timber
Peat
Asthetic value
Climate
Hazard (flood and
erosion)
Disease and pests
Pollination
Water quality
Soil quality
Air quality
Soil formation
Biodiversity
Supporting
unimproved
grassland
Very High
Low
Genetic resources
Regulating
Freshwater habitats
Livestock
Water
Cultural
Semi-natural or
Crops
Wild fish
Provisioning
Woodlands
Nutrient cycling
Water cycling
Primary production