Soil for a crevice garden

[John85]

What mixture do you use for your crevice garden?And what were the results?Any failures???
At Wisley they used mainly sand but they had problems with watering the plants.
RHS now advice to use JI n° 1 +30% grit

[ian mcdonald]

Hello John, I only have a small "crevice" garden in a trough. This has been in place for many years. I use it to grow the very small alpines that find this habitat right for their needs. It is based on troughs I saw in Ian Christies garden. I have used pieces of stone which are set so that they are pointing upwards, the stone is a type of sandstone which was used as roof tiles in an ancient building. The material used for planting was seed compost with fine grit added. I do not add any further material or minerals. Every so often I add a small top dressing of fine grit to replace frost damage etc. I find this, on a small scale, works well and the plants survive.  I don,t know what scale your crevice garden is but one thing to look for is "weed" seeds blowing in. If the resulting plants are not cleared when small then pulling them out later may disturb your alpines. Best wishes.

[Ross Barbour]

Hi John,
If your crevice is going to be bedded on regular soil then good sharp sand is perfect as you build and back fill the gaps between your rock.  Remember to leave enough space to top dress with grit or pea gravel.
The idea is for the drainage to be very sharp up by the plant, so by giving parts of your crevice good height should allow you to grow things that would other wise be a bit miffy.
A bit of extra watering might be need to establish newly planted material but the idea is to encourage rooting right down the crevice into the earth below where the moisture and temperature should be constant right through the year because of the covering of Rock.
I am growing alpines and bulbs in just sharp sand, I have build a large raised area and filled it with sand. Things are doing so well I will be taking the rest of our rock garden apart this spring  and replacing all the compost/soil with sand.
I know Ian Young uses just sand in some of his troughs and from the photos I have seen they look great.
If you are making a large crevice you could use different mediums in different areas allowing you to try different plants.
Good luck

[annew]

I used pure sharp builders sand in the top 30cm of my crevices, with the base raised on the base soil using old gritty potting compost. No problems with watering, I have watered once or twice in high summer (or what passes for such in North Yorkshire), but only to be on the safe side, and not because the plants appeared to be suffering.

[John85]

Thank you all
But the weather here is different from that in the UK:The summers are usually warm and sunny with very little rain between June and September.I have a sand bed  and I have to water it 3 or 4 times a week in summer.
I am afraid that with pure sand I will lose plants.I guess that a mixture of sand ,grit and loam will be better having some water retenton but also good drainage.But I wonder what are the best proportions.

[Jon Evans]

Far too long ago now, I went to a crevice workshop given by ZZ at the AGS Centre in Pershore.  ZZ commented that the people in the UK who wanted him to build crevice gardens usually wanted to use sand, but he recommended his regular garden soil (which was, if I remember correctly, a loam with a fair amount of clay), and said the sides of the crevice, and the use of small splits of rock to fill the top of the crevice, would provide decent drainage and cause excess rainfall to run off.  I would guess that his climate is similar to yours with long, hot summers and cold winters.

[John85]

Thank you Jon
Good news:no need to buy a lot of grit and sand.
Luckily for the gardener no cold winters here ,only very wet ones.
So the soil has to be very well draining in the winter but maintain as much humidity as possible in the summer.
I guess it will always be a compromise.
I had a look at the VRV forum about this.There the people make a very sophisticated mix with lots of ingredients!!!

[krisderaeymaeker]

Thank you Jon
Good news:no need to buy a lot of grit and sand.
Luckily for the gardener no cold winters here ,only very wet ones.
So the soil has to be very well draining in the winter but maintain as much humidity as possible in the summer.
I guess it will always be a compromise.
I had a look at the VRV forum about this.There the people make a very sophisticated mix with lots of ingredients!!!

Hi John , nice to hear that you had a look on the VRV forum 
My crevice is filled with a very lean mix . I used a mix of 7 parts sand and grit (builders sand and what we call japanese grit) + 2 parts loam  + 2 parts  bims & lava or something similar . Sometimes I add some extra gravel ....

http://www.vrvforum.be/forum/index.php?topic=428.0
 
In my experience we don't need peat or similar components . I like the results so far and must admit that we have much rain in wintermonths .
You can have a look for the kind of plants I grow there.

[Jupiter]

I'm a novice but my little rock garden is doing very well so I don't mind sharing what I've done in case it proves useful to someone. We have very hot dry summers here in Adelaide so I was very hesitant to use pure sand in my crevice garden. The topsoil in the area was a good sandy loam, so this was sieved, mostly to remove weeds, oxalis bulbs primarily. I purchased crushed quartz which ranges in size from sand up to fine grit, 5 or 6mm. A couple of wheelbarrows of this were forked in to the bed of the crevice garden before laying the stone. For packing the crevices I made a mix of 1 part sandy loam (topsoil), 3 parts crushed quartz rock, 1 part fine coconut peat (coir), two handfuls of rock dust (http://sacomposters.com.au/info/sites/default/files/FCRD.pdf), one handful of dolomite lime. So far so good. Everything I've planted in the bed is doing very well, despite what is being called severe drought in Southern Australia this spring and early summer.

[Tim Ingram]

Really interesting discussion. Several of the best rock gardens I have seen have been made on a slope with higher land above so there must be more moisture percolating through the rock-work even in drier periods. Unfortunately our garden is flat! We haven't made a crevice garden (yet) but made a sand bed at ground level by excavating the garden soil and infilling with sharp sand, the logic being that moisture in the surrounding soil would keep it reasonably moist at depth but the sand would ensure good drainage, i.e, a very simple scree (we have naturally well drained soil otherwise this would be a great way of making a sump!). This has worked quite well but like John I have sometimes had to water in dry summer periods - as plants establish, especially deep rooting species, this becomes less needful. The other factor is the plants themselves. If these are all small and naturally slow growing then transpiration of moisture will be low and a deep bed of sand is good at holding moisture when the surface dries out. Crevice gardens are good because the rocks mean you can't have so many plants! or rather grow smaller ones (and deep crevices must be just like deep pots - ideal for rock plants and bulbs).

We certainly don't grow plants as well as Kris or in the Czech gardens which is why a crevice garden beckons if we can find a cheap source of stone. But sand beds are very effective in many climates and don't cost too much to make. This is what the 'soil' looked like in one of the Czech gardens - pretty much just sharp sand - but here the rock garden is on a slope.

[mark smyth]

Bottom half of my crevice bed is contents from dead plants in pots topped with sand. After 10 years mine is crying out to be replanted

Don't trust others to recycle 'dead' pot contents!

Anemone nemerosa 'Robinsoniana' now spreading over half of my crevice bed and coming up through 20-30cm of sand and stone

[penstemon]

The very idea that there can be such a thing as "cheap stone".... Where I live, reasonably close to the Rockies (see picture I just took sitting in this chair; zoomed in a bit), purveyors of stone insist on selling it by weight.
I don't have a crevice garden. The logic behind them escapes me (alpine plants don't need to grow next to rocks) though I do admit most are very attractive.

[Rick R.]

Baldassare Mineo also advocates a richer, clay base soil in cracks and crevices.  Although I believe in his mind, these crevices are narrower than what is usually in a crevice garden.

[penstemon]

If a plant is adapted to growing in coarse soil, the roots have a difficult time pulling water from clay soils. During drought, water is more quickly withdrawn from clay than from coarse soils, so plants growing in clay would have to be irrigated. Most plants grow in coarse soils in order to capture every bit of rainfall (nothing to do with "drainage").
In semi-arid and arid climates, and also above timberline, the evaporation rate is very high. Evaporation exceeds percolation in dense-textured soils in such environments.
So, for example, in my sand and gravel piles, a typical thunderstorm might drop 1cm of rain, almost all of which goes to the plants' roots, but in the clay soil in the "meadow', no rain goes to the roots. A day-long rain (rare here) would be necessary for the plants in the meadow to be adequately watered.
Another problem with clay is the lack of oxygen. It would seem to me that a crevice filled with clay would be especially prone to having the oxygen driven from the soil. (Followed by a buildup of respirated carbon dioxide and root asphyxiation.)

[Tim Ingram]

Bob - have you never seen an alpine cushion plant growing out of the narrowest crevice amongst rocks? This is their métier . The traditional recipes for screes from the great days of alpine gardening generally used sharp sand and grit with a soupcon of leafmould, probably very much like you find in natural screes and cracks amongst rocks. So much depends on the sort of plants you want to grow and Joe Elliott put rich manure into the base of his troughs of spring gentian - a 'meadow' plant that grows in rich well drained (have to say this, but aerated is more accurate) soil, whereas something like an eriogonum is much better in pure sand, and of course sand does soak up every bit of moisture in a dry climate, and on a big enough scale works just as well for Peter Korn with 60" of rain in Sweden. Essentially I agree with you. When growing plants I think it is very much horses for courses, especially if you have catholic tastes, but really choice alpines do test the gardener!