rhododendron and soil ?

[Catwheazle]

Hello,
so far I was always in the belief that, except as the home of rhododendron rhododendrons
need acidic soil.
On my trip to Hunanlong, China, however, I had countless staggeringly beautiful rhododendrons
Lime, z.T. seen directly on sintering.
Was on the signs:
anthropogonoides, capitate pachytrichum, hunnewellianum ssp. rockii, sichangende var exquisitum, grande
and qinghaiense called.
Thrive here on my limestone? The climate of the Alps should not mind traveling?
Are the plants or seeds which ever available here in Europe?
Maybe someone knows these plants and has experience with their culture.
LG
Bernd

[Maggi Young]

Bernd, it can be done.    This article "Non-Conformist Rhododendrons"  by Prof. David W.H. Rankin, well known SRGC member, will be of use I am sure.

For further reading, there is also this thesis, by Maria V. Kaisheva -
"The effect of metals and soil pH on the growth of Rhododendron and other alpine plants in limestone soil"
Authors:    Kaisheva, Maria V
Supervisor(s):    Rankin, David W H
Issue Date:    2008
Abstract:    Rhododendrons are economically important plants in horticulture, and many species are threatened in the wild by habitat degradation. It is therefore doubly important that their nutritional needs should be understood.
You can open or download the whole document HERE

There is also this article :
    'Growing rhododendrons on limestone soils: is it really possible? '
Authors
    McAleese, A. J.; Rankin, D. W. H.
Journal
    American Rhododendron Society Journal 2000 Vol. 54 No. 3 pp. 126-134
ISSN
    0745-7839
Record Number
    20000314532    ...... but I am not sure if there is an online version.

[Catwheazle]

great 

thx
Bernd

[Mavers]

Very interesting subject.

I recall at a Malvern spring show several years ago seeing a new type of rhododendron that could be grown on limey soil. There was a range of colours for sale.

[Alan_b]

... a new type of rhododendron that could be grown on limey soil.

They have not caught on.  The soil in my area is limey and you don't see rhododendrons anywhere.  Magnolias, yes, so at least some of those species will grow despite the limey soil and low rainfall.  But rhododendrons never. 

[Catwheazle]

Magnolia stellata is growin well in my garden (rocks and limestone)

[Anders]

Here comes a long story. For the moment, I am doing field work at Kangerlussuaq, western Greenland, and it is a pleasure. The air is 12 degrees C, the sun is shining and our field plots are covered with Rhododendron tomentosum and Rhododendron lapponicum. Both rhodos cover squarekilometer after squarekilometer, but their habitats almost never overlap.  Here, the rhodos are not the fat specimens that we see in the gardens, both species may reach 15 cm close to the sea at Lake Helen, but they barely extend 2-5 cm above the ground from the Russel glacier and towards the ice cap. The climate is arctic semi-desert with less than 100 mm precipitation at the inner half of the valley. The wind blows from the ice cap down through the valley towards the sea so the air is dry, but the ground is wet in many places due to melt water.

R. tormentosum and Betula nana cover the protected northern sides of the mountains that stay cold and humid during summer. These north-facing mountain sides have a thick moss cover and a thin humus layer and remain humid due to the permafrost which is only 35 cm below the surface. The permafrost prevents the water from draining away, and the ground temperature at 10 cm depth is less than 2 degrees Celsius. Here,  R. tomentosum is protected from drying out by a layer of snow during winter. The climate at the top of the small mountains is too harsh for R.  tomentosum, even on the northern sides where R. lapponicum takes over together with Cassiope tetragona. R. lapponicum seems to prefer extreme habitats that are exposed to wind and sun. It grows on the dry south-facing mountain sides, on wind-exposed sand dunes, and in calcareous fens. Many of its’ habitats have a neutral to slightly alkaline pH, very little organic matter, and often no snow cover to protect against the dry winter winds. One of our field plots is a small lapponicum-sedge fen close to Lake Helen. This fen is characterised by low precipitation and high evaporation so that the ground in autumn is white in many places from precipitated carbonates. Alkaline and salty, this is not a place where I would have expected Rhododendrons.   
 
The first picture is a view from our field plot at Mount Sugar Loaf where the spicy smell of R. tomentosum drifts along the hill side. The second picture is a close up of R. tomentosum at Lake Helen where it grows together with Betula nana, Salix and sedges.
Picture 3 shows an R. lapponicum habitat at a small ice-cold melt water lake in front of the Russel Glacier. Notice the large edge moraine that the glacier has pushed in front of it. Picture 4 is from the same place as picture 3, and shows the harsh conditions that lapponicum prefers, the vegetation does not cover the ground, only mosses survive between the lapponicums. The white stuff is dust from the sand storms.

Picture 5 shows the habitat of R. lapponicum where it grows close to the Russel glacier. Picture 6 is from the edge of the icecap, where lapponicum grows close to the ice edge in ice-cold soil that is pure inorganinc moraine with no traces of organic matter.

What does this mean for rock gardening? Well, it seems that not all rhodos need low pH and peat. I have tested another species from the lapponicum series (R. impeditum) in my garden and it grows happily in an inorganic, neutral soil. The leaves are more blue than normal but there are no signs of chlorosis yet. But I guess that tomentosum would require both peat and low pH.
 
Anders

[Anders]

...and here comes the last three pictures.

Anders

[Catwheazle]

great :-) lot of thanks !

Bernd

[Maggi Young]

Anders, you are indeed fortunate to have the chance to spend time in such a wild and interesting place. Thank you for sharing this with us.