Rhododendrons; scourge or not?

recedite · 28-06-2014 4:40pm #1

I see there are calls for more money and more volunteers to "eradicate" this plant in Kerry.

Admired for its beauty but loathed by nature lovers because of the damage it causes to native flora and fauna, the rhododendron is considered an invasive nuisance plant.
This week, Heritage Minister Jimmy Deenihan committed €100,000 to Killarney National Park on top of the €500,000 that has been allocated to deal with the rhododendron problem by his department since 2011. But Trevor Halpin of Groundwork says this is not enough and the plant is in danger of re-establishing and taking over large swathes of parkland.
A couple in their fifties endured a five-hour ordeal after they became trapped in a forest of rhododendron plants on the Knockmealdown Mountains on the Waterford/Tipperary border earlier this week.

- See more at: http://www.independent.ie/irish-news/news/more-work-needed-to-rid-park-of-nuisance-rhododendron-30370228.html#sthash.Tucs3BPV.dpuf

An online petition has been launched.

I cannot see it ever being "eradicated" as such. Controlling it where growing conditions are good is like mowing a lawn; it is just ongoing, never-ending work. In much the same way rats cannot ever be eradicated, but they can be denied a suitable habitat to live in. They only appear in any numbers where food is left lying around.
I have only seen a few patches of rhododendron around Wicklow forests, just at the edges, but it does not seem to be able to grow beneath a dense forest canopy. Most forests in Wicklow are fairly dense, even the broadleaf ones. In some places foresters have controlled patches of it, in others it was left alone and it just wasn't able to spread.

In Killarney, the trees are very sparse except in some areas around Torc Mtn. near the waterfall. Is this considered a "natural" state for the forest there, or is it just the result of people grazing their sheep and gathering firewood over the past few hundred years? For decades now volunteers and national park staff have been hacking away at the rhododendron. I wonder if the conservationists concentrated on planting oak trees, and looking after them for the first few years until they got established, would the "rhododendron problem" then cease to be "a problem"? In some very rocky places where the trees cannot thrive, just concede those areas to the rhododendron?

magicbastarder · 28-06-2014 8:02pm

one of the problems with it is that it has a symbiotic relationship with a bacteria which lives around its roots, which suppresses all other germination (i may have the details wrong here), so the problem is that once it takes over, there's nothing else but rhododendron.

i'd agree with you that we will never be able to fully eradicate it, unless someone invents a pathogen which will kill it and only it.

i've seen it in places like the grounds of ballynahinch castle where in places, it has taken over and there is not much else thriving.

Capercaille · 28-06-2014 10:20pm

recedite wrote: »

I see there are calls for more money and more volunteers to "eradicate" this plant in Kerry.
- See more at: http://www.independent.ie/irish-news/news/more-work-needed-to-rid-park-of-nuisance-rhododendron-30370228.html#sthash.Tucs3BPV.dpuf

An online petition has been launched.

I cannot see it ever being "eradicated" as such. Controlling it where growing conditions are good is like mowing a lawn; it is just ongoing, never-ending work. In much the same way rats cannot ever be eradicated, but they can be denied a suitable habitat to live in. They only appear in any numbers where food is left lying around.
I have only seen a few patches of rhododendron around Wicklow forests, just at the edges, but it does not seem to be able to grow beneath a dense forest canopy. Most forests in Wicklow are fairly dense, even the broadleaf ones. In some places foresters have controlled patches of it, in others it was left alone and it just wasn't able to spread.

In Killarney, the trees are very sparse except in some areas around Torc Mtn. near the waterfall. Is this considered a "natural" state for the forest there, or is it just the result of people grazing their sheep and gathering firewood over the past few hundred years? For decades now volunteers and national park staff have been hacking away at the rhododendron. I wonder if the conservationists concentrated on planting oak trees, and looking after them for the first few years until they got established, would the "rhododendron problem" then cease to be "a problem"? In some very rocky places where the trees cannot thrive, just concede those areas to the rhododendron?

Invasive species of the highest order. Preventing regeneration of oakwoods in Glendalough as well. Big problem with spread in places like Achill Island.

deise08 · 28-06-2014 10:26pm

Doesn't the Rhodedendron carry a disease that causes cankers in oak trees?

magicbastarder · 29-06-2014 8:52am

and achill has the problem with gunnera too.

Judgement Day · 29-06-2014 8:58am

The Knockmealdown Mountains story sounds like something out of John Wyndham's novel "The Day of the Triffids" - is there any danger that the rhododendrons will breakout of the Killarney National Park and kill us all in our beds?

robp · 29-06-2014 10:35am

recedite wrote: »

I have only seen a few patches of rhododendron around Wicklow forests, just at the edges, but it does not seem to be able to grow beneath a dense forest canopy. Most forests in Wicklow are fairly dense, even the broadleaf ones. In some places foresters have controlled patches of it, in others it was left alone and it just wasn't able to spread.

In Killarney, the trees are very sparse except in some areas around Torc Mtn. near the waterfall. Is this considered a "natural" state for the forest there, or is it just the result of people grazing their sheep and gathering firewood over the past few hundred years? For decades now volunteers and national park staff have been hacking away at the rhododendron. I wonder if the conservationists concentrated on planting oak trees, and looking after them for the first few years until they got established, would the "rhododendron problem" then cease to be "a problem"? In some very rocky places where the trees cannot thrive, just concede those areas to the rhododendron?

Now perhaps people will disagree with me but I would think Killarney is in anything but a natural state. Very little tree regeneration occurs there due to huge levels of deer and even sheep overgrazing. Also the tree line is far lower than it naturally would be. If there was less overgrazing there would be far more young thickets of oak, birch that would been less susceptible to rhododendron. I don't know the best solution but overgrazing should be reduced. I do think complete elimination of rhododendron is possible if enough will is put into it.

recedite · 29-06-2014 5:45pm

robp wrote: »

Now perhaps people will disagree with me but I would think Killarney is in anything but a natural state. Very little tree regeneration occurs there ....

I agree it is not really in a natural state, but it is a "pleasant" environment (apart from the ever-present drone of chainsaws in the distance cutting the rhododendron) for people (tourists) to view. The kind of open parkland around the Muckross estate cannot exist for long without management, but even further out around the lakes and mountains, much of the land is semi-open, almost like parkland. Which is ideal terrain for a managed shooting/hunting estate, and maybe that was its function in the past. But semi-open terrain also encourages shrubby plants to take over at ground level unless it is carefully managed and grazed.
I think the mistake they are making in Killarney is to think that when (and if) the rhododendron is eliminated, then "natural regeneration" of the oak will follow.
They would be better off growing oak saplings in a nursery and planting them out in a managed way behind proper deer-fences. In some places they have fashioned deer-fences out of piles of cut rhododendron, but that is almost an afterthought.

magicbastarder · 29-06-2014 6:01pm

i wouldn't have considered it an afterthought - i had understood it was part of the policy for dealing with the rhododendrons?

Pat Mustard · 30-06-2014 1:12am

In relation to the hassle caused to those hikers in the Knockmealdowns, the BBC covered the story well.

http://www.bbc.com/news/world-europe-27882358

Jimmy Barry from the South Eastern Mountain Rescue Association said the rhododendron forest was so thick and deep that people could not hear each other.

"It was horrendous - I have been a member of mountain rescue for 15 years and it was probably one of the most dangerous exercises or rescues I've been on," Mr Barry told BBC Radio Ulster.

The plant's dense foliage tends to block out sunlight and kill off surrounding vegetation.

Mr Barry said this meant the rhododendron forest had produced very difficult terrain on the mountainside.

"It's regarded as a weed. It's not a native plant to Ireland or any part of the British Isles and they've just gone wild," he said.

"It looks beautiful, but underneath it nothing of our native plants grows, and it's just horrible in there.

"Dangerous, because where it was growing on the side of the lake, it's very steep ground, so we were literally walking on rhododendron.

recedite · 30-06-2014 11:45am

In Wicklow, any hilly land that is not forest, and not maintained as grazing land either, tends to become overrun with gorse. The gorse is a native plant that requires a bit more light but seems to fill a similar ecological niche to rhododendron, and is just as annoying for hikers.
On Bray head, people have been planting oak and beech saplings on the burned ground left after the frequent gorse fires. This has been going on for many years, but eventually the trees seem to get killed by the fires.
If you want to stop gorse or rhododendron, turn the land into either forest or pasture. One or the other, but not a mixture of both. Unless you are prepared to put a lot of effort into maintaining a parkland landcape.

Desmo · 30-06-2014 11:54am

The Rhodendrons in Killarney are especially tragic. The landscape is not 100% natural as the trees are just regrowth after being felled a couple of hundred years ago and there is overgrazing but they are the most species rich oak woods in the country (esp mosses and liverworts). It is a unique habitat due to almost complete lack of frost and huge rainfall. It is perhaps the most interesting/unique habitat in the country. The rhodos wipe out everything; it really is disastrous.

Des

Birdnuts · 30-06-2014 4:27pm

The Mustard wrote: »

In relation to the hassle caused to those hikers in the Knockmealdowns, the BBC covered the story well.

http://www.bbc.com/news/world-europe-27882358

You'd want napalm to deal with that level of infestation:(. The spread of invasive plants needs to be taken alot more seriously in this country!! Some of the worst examples of this phenomenon is on state land such National/Forest Parks:mad:

Capercaille · 30-06-2014 9:11pm

recedite wrote: »

In Wicklow, any hilly land that is not forest, and not maintained as grazing land either, tends to become overrun with gorse. The gorse is a native plant that requires a bit more light but seems to fill a similar ecological niche to rhododendron, and is just as annoying for hikers.
On Bray head, people have been planting oak and beech saplings on the burned ground left after the frequent gorse fires. This has been going on for many years, but eventually the trees seem to get killed by the fires.
If you want to stop gorse or rhododendron, turn the land into either forest or pasture. One or the other, but not a mixture of both. Unless you are prepared to put a lot of effort into maintaining a parkland landcape.

Gorse is a great plant for wildlife.

Desmo · 01-07-2014 3:32pm

have to agree with Mr. Caille here. Gorse is Good!

Cork boy 55 · 21-10-2014 11:37pm

The Control of Rhododendron
in Native Woodlands

Author: Chris Barron, Woodland contractor

Edited: Declan Little, Woodlands of Ireland

CONCLUSIONS
Rhododendron (and laurel) poses a
serious ecological threat to native
woodlands in Ireland, particularly by
displacing native vegetation and by
preventing the natural regeneration of
native flora. This results in the disruption
of woodland succession and continuity,
with a consequent reduction in woodland
biodiversity. The future survival of badly
infested woodlands may be seriously
compromised and even impossible.
The control and/or eradication of this
invasive alien species requires long-term
planning, a good understanding of its
ecology, and a thorough application of
initial clearance and follow-up activities
such as stump uprooting and/or herbicide
treatment (Fig. 4). Timing of herbicide
application as well as weather conditions
are very important factors and must be
taken into account. The control of
seedlings and the regrowth from cut
stumps involves ongoing spot checks
and monitoring.

http://www.woodlandsofireland.com/sites/default/files/Rhodo.pdf

Rhododendrons; scourge or not?

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