Scottish Rock Garden Club Forum
General Subjects => Blogs and Diaries => Topic started by: Tristan_He on August 20, 2016, 12:53:06 PM
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I've mentioned to this in some posts before but I thought it might be interesting to bring some of this together and try to explain what I've been doing with / to some of my plants! I live in a cottage in the hills of North Wales, and quite a bit of our garden has walls of various types and standards of construction. I've wondered about what sorts of plants could grow in these conditions. Lately green roofs and green walls have been quite in fashion, but the types of plants grown in these have been quite unadventurous (Sedums and er.. more sedums). So... I have been playing around with my own walls. Here they are:
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This is a dry-stone boundary wall with mortar cap and coping at the top. It was raised about 3 years ago to make it sheep-proof. Although south-facing the lower, older part gets a good bit of shade from the house and has a good coating of mosses. The north face is not really cultivatable sadly as there is a nettle-bed, and it would be accessible to sheep grazing. I'll call this the heath wall.
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Self-sown Polypodium and moss on the heath wall.
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We also have a ruined outbuilding that we have capped off to stabilise it. This is also dry stone I think but with a strong vertical face. It's sunny and faces west, so gets the full force of the prevailing weather.
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I'll call this the road wall. It is the boundary wall that runs north-south, then does a right-angled turn to run east-west before doing another shorter north-south run. This wall is mortared so no opportunities for alpines there (should have thought of that when we built it...). But there is a deep slate coping on top which provides lots of potential crevices.
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Finally this is the boundary with next door. It's a pretty rough bit of stonework - I think about the best you can say is that it hasn't fallen down. However, it faces north and is shady, so lots of potential niches. I haven't really done much with this yet but the polypody seems to like it.
Obviously this is an extreme environment. To start with there isn't any soil. Some needs to be provided, but then again many alpines in the wild seemingly grow with minimal soil anyway, in tiny crevices in boulders or even among mossy cushions. I didn't have the luxury of building soil in with the walls (and I'm not sure if this is really a good idea anyway, too many weed opportunities). There will also be extremes of temperature and water. So... what survives, what thrives and what dies? And how do you establish plants in an environment where it's difficult to get soil into cracks, and which is really difficult to water?
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At the tops of the walls, the copings are an obvious place to start. The heath wall copings are fairly shallow:
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But the slate copings on top of the road wall are deeper. Even so, there is only room for an inch or two of soil.
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Houseleeks (Sempervivum) are an obvious choice in this environment. I've lost the label for this one but I think it might be an S. calcareum clone. It's a good doer. The poor soil helps them develop a good colour. I used garden soil for this and you can see there is a volunteer primrose in the background! Also a few celandines have popped up, though they don't flower.
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S. 'Sprite' is a favourite of mine.
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I can't remember what this one is. There is a label but it is buried and I'd have to pull apart the plant to find out! Anyway, it's a nice tight cushion.
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Here are some more plants on top of the road wall.
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Veronica sp. prostrata - thanks Trond! This was here when I bought the house and should really have found out what this is by now. It seems to like the wall and stays more compact than elsewhere in the garden. You can see Sedum anglicum in the background - unfortunately this is rather a nuisance as it has seeded liberally into the rockery below. S. reflexum, album and spurium are all doing fine as well, not surprisingly.
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Geranium cinereum, again nice and compact in this sunny nutrient-poor location. I thought it might suit Erodiums too but they have mostly died.
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A Lewisia cotyledon hybrid has not done too well either. It is surviving but not really growing or flowering.
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Globularia meridionalis is growing, but rather slowly and hasn't flowered this year. I'm hopeful it will do something though. Maybe I will give it a weak feed to encourage it.
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This Campanula cochlearifolia is from seed I collected last year, and I was quite surprised to see it flower already. Hopefully it will establish.
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Dianthus 'Whatfield Magenta'. This seems a good place for pinks, the white unidentified 'not superbus' that I posted earlier in the year on another thread also does well here. However, it is a bit too dry for D. deltoides which shrivelled up during a dry spell in June. It has perked up again now but does seem to struggle a bit.
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I have also planted some spare seedlings of D. pavonius in among the coping.
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Saxifraga sp - I'm not very careful with labelling pieces that I tear off but I think this may be cochlearifolia?
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Sedum sexangulare.
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Tristan,
a very exciting project! Seems you have found several suitable plants already. I can recommend several of the silvery saxifragas. Here they seed in the thin moss cover of rocks and stones. They also like mortar. (Maybe the Lewisia dislike too much Calsium?)
Saxifraga cotyledon do not need much soil, just a crack or a thin layer of moss is enough.
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Small ferns like Aspleniums do very well in such walls. Also sea thrift will grow there. They are best planted as small seedlings!
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Brilliant idea to start this thread, Tristan! Thanks!
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I second that Maggi. As a lover of plants in stone walls I'm fascinated to see your experiments and results Tristan 8)
Here in Ireland many villages and rural communities like to participate in a 'Tidy Towns' competition. Unfortunately this may include 'tidying up' old stone walls by removing vegetation. Ironically this reduces the charm of old bridges and similar structures built with soft mortar that could be colonised over time. More serious harm is done by spraying glyphosate on our traditional ditches (earth banks faced with stone, widespread in Ireland) which depended on plant roots for stability and therefore begin to collapse >:(
Could your Veronica sp. be officinalis, the heath speedwell?
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I go for Veronica prostrata ;)
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The great thing about this kind of garden is that there is virtually zero maintenance. Weeds don't really seed into it and if they do, growth is slow and they are easy to remove. Slugs don't make it to the top and it's not necessary to worry about drainage or watering (at least once the plants are established). Planting is more of a challenge however! I wedge in a couple of stones at the end of the crevice to help stop soil washing out.
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Hi Trond, I think this is my Sax cotyledon (or a hybrid of it). It's on the heath wall and definitely seems to like it! The Lewisia looks a bit underfed to me, maybe I just need to give it a weak feed. What is the Campanula in the background of your photo? I think this environment could be quite good for saxatile campanulas, not as many slugs.
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Also thrift is a great idea, I'll collect some seed when we go to the beach.
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Yes, this is an exciting thread Tristan and I think everyone can contribute a bit to it and maybe help you with the plants choices.
I find a great similitude between your stone walls and the alvars habitats from Ontario, especially the shoreline alvars. It is fascinating to watch plants growing in thin rock fissures on just tiny amounts of sediments/moss.
Campanula rotundifolia does very well there, accompanied often by other species like Primula mistassinica, Viola nephrophylla, Packera, a dwarf Solidago and so on....
And as you just mentioned, there is no weed competition in these tough situations :)
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Campanula rotundifolia, to which Zdenek Zvolanek replied with - "I like this mighty circus of walls" - when I put this picture at Malham Cove on Facebook. They do really well in the sand bed in our garden, seem to grow on nothing!
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C. rotundifolia is a lovely thing isn't it? We don't grow it enough in gardens, I suppose as the saying goes, familiarity breeds contempt. There is a nice patch along the road not too far from here, I always mean to collect seed.
'A mighty circus of walls' is a brilliant description of Malham Cove - a bonkers landscape that looks as though it cannot possibly be natural.
I've put a couple of pieces of Campanula pulla on the top of the wall today, the rain will help water it in.
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Ashley, I agree, very sad how some people feel the need to 'tidy' everything.
'Tidy Towns' always makes me laugh. In Britain we always seem to give things grandiose or impressive sounding names - Royal this and that, or Britain in Bloom. Ireland is so much more down to earth.
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Gabriela, had never heard of alvars, just Googled them. They look fascinating, perhaps worth a thread in their own right?
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Hi Trond, I think this is my Sax cotyledon (or a hybrid of it). It's on the heath wall and definitely seems to like it! The Lewisia looks a bit underfed to me, maybe I just need to give it a weak feed. What is the Campanula in the background of your photo? I think this environment could be quite good for saxatile campanulas, not as many slugs.
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Also thrift is a great idea, I'll collect some seed when we go to the beach.
In the nature bergfrue (Sax cotyledon) grows both in full sun and shade and flower reliable. I have seen a lot of it!
The Campanula is the common harebell, C. rotundifolia :) It is very variable here and several ecotypes/forms exist but they are not clear cut. Here are some flower forms from our cabin collected in 5 minutes (a few years ago).
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It is commonly found in crevices like this:
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. . . and in meadows like this:
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Some more plants, now coming down the wall a bit. These are on the south-facing heath wall, although it's not exposed to sun all day due to shade from the house.
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Some spare bits of saxifrage were planted here - S. 'Gregor Mendel' I think, also a purple hybrid. They settled in rather slowly last summer and growth has been slowish, but they are doing ok now. To be honest they have done better than I expected as the aspect isn't ideal.
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Another larger saxifrage. Not doing as well as the cotyledon.
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Houseleeks look good on their side too. That's a real cobweb, rather than S. arachnoideum parentage!
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This Erodium 'Natasha' is struggling though.
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Another saxifrage, planted more recently.
Planting in these situations is quite a challenge. I tend to use pure, sterilised topsoil as drainage isn't an issue, but drought certainly is. I used to try to scoop this in dry direct from the bag, but this was problematic as (i) a lot of it used to fall to the ground and (ii) it's very difficult to water vertical crevices without washing the soil out again. To overcome this I wet the soil beforehand until it is about the consistency of wet cement, then shove as much of it as I can into the gap. Effectively this creates a pre-watered planting pocket. Then, I plant into this. Due to the difficulty of watering it's also better to plant during a period when it's not too dry, to give the plants the maximum chance of establishment.
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Lovely rotundifolias Trond.
In Slovenia we came across a fair bit of C. cochlearifolia in the tiniest crevices.
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I have tried to replicate this by planting small plants into crevices. We'll see how they do.
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This Sempervivum calcareum variety looks great near the top of the ruined outbuilding. It's growing well too.
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Finally for now here is my favourite rockery planting tool!
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I pushed soil into my wall crevices from an old coal shovel. The shovel was held below the gap and the soil pushed in using a piece of wooden dowel and then rammed in quite hard as far as it would go. I had more success with plants that were very small to begin with. Seed can be blown in the crevices as in nature.
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A bit of an update on this thread just showing what's flowering at the moment and how plants have established.
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Dianthus 'Whatfield Magenta' has slowly made a good compact clump with a nice shape.
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Lotus corniculatus. I can't remember if I put it there deliberatley or if it arrived by itself. However it looks great here and stays really compact. Some years if it is very dry it gets frizzled up but it has always bounced back after rain.
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Dianthus alpinus, a 'Joan's Blood' seedling. I have this in the rockery too but the slugs like to chew it there. Here is is a bit harder and there are fewer molluscs. Unfotunately I have to crane over a bit to admire this plant.
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Edraianthus pumilio. Funnily enough the slugs here don't seem to go for this one, even though almost everyone else mentions how slug prone it is (I also have three in a pan in a much more sluggy part of the garden and one on the rockery right next to the chewed Dianthus alpinus mentioned above). All my E. pumilio were grown from alpine-seeds seed a few years ago.
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Minuartia langii is a new one I am trying. So far it looks promising. These are the first flowers.
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Sempervivum are not a very original choice for this setting, but they look very good here.
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Dianthus pavonius. Although dwarf, this has quite long airy flower stems that are difficult to capture. It is an easy pink that self-seeds gently in the rockery.
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A view up part of the wall - the purple is Erinus alpinus which makes itself a little too at home here! Still, it's very pretty.
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Edraianthus niveus.
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A nice little Helianthemum growing with Sedum anglicum.
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I am thinking of trying a few bulbs here, though of course the soil isn't very deep which is tricky. Probably seed or seedlings would work best. Any suggestions?
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Tristan, spring squill grow in thin turf at the coast.
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That's a good idea Ian, thanks. Funnily enough I have a couple of year-old bulbs in a pot. I'll see if I can get hold of some seed as well.