The eurasian magpies are my favorites, but considered invasive here in Argeş. Almost nobody likes them here, buy I think they’re smart and social.
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I doubt A. altissima alone was the cause of the dieback of the patch of trees.
It probably had help from something else (droughts, invasive species of fungal pathogens, insects, improper forestry practices …, probably all of the above), and Ailanthus just finished them off.
I am doing my PhD on the Slovene part of Triestine Karst, and yes, while the Ailanthus is definitely present and most definitely problem, it absolutely cannot compete with helathy native trees to the point of excluding them; esp. cerris oak, manna ash and hophornbeam are perfectly fine in shading it out and even killing it. In most mature stands of forests on Slovenian part of Karst it just hangs out in the shade under the oaks, not doing any damage.
It’s problematic in areas where native trees cannot / are not allowed to develop properly (the absolute worst is the scrub under the powerlines), and in those areas we should really demand that grasslands be maintained in those areas (as an added bonus, those grasslands would be amazingly biodiverse).
If I had to pick the most problematic tree on Karst, definitely Robinia pseudoacacia. Where fire destroyed the oak-ash forest, some of our plots are now 100% 2-year old robinia.
The second would be Pinus nigra (it makes fires go WOOM).
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Invasive plant in the wider sense (just not-native and naturalised): Impatiens balfouri
It is always nice to see it, It has interesting flowers and does not seem to be able to do any real damage. It does not form stands lake the other two invasive impatienses, there is just a clump or two in the gravelbar.
The real invasive plant (i. e. it does do damage):
Paulownia tomentosa. This tree started popping up everywhere in the forests around here, and while I do not think this will be a horrible invasive (after all, it is a short lived pinoeer tree), it is worrying how many and in how far apart I have seen young plants of this tree,
It is however, very beautiful, the big leaves and the purple flowers look very exotic.
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I agree. From what I have seen it is to a very large extent absent/improper forestry practices and disinterest.
A. altissima can predominantly be found on disturbed sites. After the entire road network on the Carso above Trieste had been restructured, the former work sites (especially the cleared areas where the large road building equipment had been kept during the operation) were left very much unattended afterwards, making it ever so easy for A. altissima to take hold. They beat the native species to re-colonizing those areas.
Further inwards, away from those disturbed sites, where older patches with native trees still stand (I don’t recall noticing Quercus cerris, but definitely Ostrya carpinifolia, Carpinus betulus, Quercus petraea, Quercus pubescens, Fraxinus ornus, Acer monspessulanum), A. altissima has it tougher, but it does try to make inroads there too. On my frequent dog walks I had the impression that the plant is helped along on the smaller roads by disinterested/unaware former city dwellers who own the adjacent plots. They don’t realize what those plants are, or don’t see why they should invest time and effort (and are reluctant to spend what little money they may have left over from building/renovating their new home) in removing those trees from the boundaries of their properties (“they’re growing by the road/let the municipality worry about that/not my concern”).
Also, small plots of undeveloped land along the autostrada that cannot be used for residential or agricultural purposes are often purchased by folks who live in the city for their week-end leisure activities or with the intent of using the wood growing there as fire wood. Once the sites are cleared, however, some are left to themselves (for whatever reason). I know one patch in particular that was cleared and is now entirely covered by A. altissima, with nothing else competing there. The adjacent plot (one that had always been owned by a local farmer), planted with olive trees, is kept meticulously clear of A. altissima.
The Pinus nigra falls into the category ‘forestry practices’. The Austrians had all the best intentions when they planted millions of these on the Carso in the second half of the 19th century.
As for Robinia pseudoacacia while its cultivation is discouraged, it is nevertheless omnipresent. It (re-)grows fast (fire wood users like that), and beekeepers count on it for the inexplicably commercially successful but not really particularly good ‘acacia honey’. On top of that, locust trees even survive goats. Actually, goats prefer young Fraxinus to young Robinia, so they’re not much help anyway.
The Pinus nigra stands, if left to natural succesion (they cannot rejuvenate in their own stands, only colonise abandoned pastures) have been instrumental in reforestation - they enabled enough soil to accumulate for deciduous forests to re-grow, and in 19. century, the area was not so hot and drought prone. It had a time and a place.
But currently, with the new climate, Pinus nigra is wholly unsuited, it is surprisingly drought intolerant for a pine. When I heard some foresters were planing to re-forest that big burnt area in the north of Kras, I facepalmed so hard. I takes 5 min of walking through the fireplace to see why it was so bad. Fortunately, someone convinced them this is actually a really bad idea (actually the whole active reforestation is stupid, what should be done is regular checking of plots to remove the alien trees, and do passive reforestaion; leave the rest to natural succesion, planted trees, even small seedlings cannot survive in the stony ground) …
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Totally agree. The ground is so stony, the costs will be stratospheric. Natural succession will in the end produce better results (in line with the changing climate) and cost less.
yes, those abandoned and disturbed lots are a big problem.
The worst case I know in Slovenia, is on the Karst edge above Podpeč under a powerline, where previously species rich grasslands and shrubland grew
Where Ailanthus is native, it is a relatively short lived, pioneer tree; so hopefully those monocultures will also be shortlived? I know it is allelopathic, but the effectiveness of that usually wears off after some time?
What, allelopathy wears off? I wonder when that will happen. In my yard, Juglans regia (also allelopathic) makes the other fruit trees grow their branches away from the direction where the walnut tree is. Also, whether allelopathy wears off or not, I see loads of young walnut trees popping up everywhere like weed. Ailanthus is also good at spreading its seeds.
And its cousin of pure evil, Himalayan balsam.
I’ve heard California Poppy is invasive in the Canary islands. It’s such a pretty flower with super soft petals so i’d love to see invasive California poppy. I suppose it looks much like the hills in California that get covered in it, except it’s native there and only blooms like that some years.
The introduced lupine in Iceland is pretty epic as well. It’s a bit complex in terms of invasiveniss, in some areas it does seem ivnasive but in other areas it seems to just be regrowing in areas there is no soil (from land use? or just beacuse it’s a volcano? i don’t know). Iceland and the UK both seem a lot less straightforward on how inavsive plants work versus North America.
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Oh I really hate them! I have tried destroying many, I also dislike their smell when you break them. But I do respect their strenght and survival abilities in the concrete jungle.
There are some patches where I try to cut all saplings/regrowths but it never stops! They are impossible to kill…
I like to see invasive plants that come from America or Asia in Europe, gives me a revenge feeling… I know, is sick!
Especially I like the pink flowered oxalis clover you cannot get rid of in the garden.
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