Update on the Wisley Crevice Garden

[Maggi Young]

Paul gives us an update on the planting of the crevice garden in the latest log:
http://www.srgc.org.uk/logs/logdir/2011Jun081307557574Log_6_of_2011.pdf

He raises some very interesting points... such as the failure of smaller plants to "take" in the planting, when it is usually suggested that this is the best method of establishing plants in crevices.....
and..... why is it so hard to water the sand? 

[Lesley Cox]

Sand that has become VERY dry, can form a crust on top and it has to be watered very carefully and slowly to absord rather than run off but I can't imagine this would be the problem with the Wisley crevices. Maybe some dusty or powdery content in the sand is rejuecting water?

I'm sure it is perverse of me but somehow all those brightly coloured flowers look - to me - out of place in what would seem to be a mountain scene. Too much colour for the area of mountainside. Sorry.

[John85]

Hello Paul
The same thing occurs here but I must confess I am looking for problems as I use mostly reclaimed sand that I get from different sources.It is a bit surprising that you got the problem with washed sand!Or may be you got a load that wasn't washed properly.(remember, I asked what you used a couple of months ago)From my own experience I'd say it is mostly the dust that makes the sand hydrophobic:I got a load from the local council of blown over dune sand from the promenade.It was clean and had no problems.The second load of exactly the same sand but swept from the street contained dirt and was hydrophobic.
To be able to use it nevertheless I added 10% of good garden soil and"compensated" by adding 25% of 2/4mm grit.It worked for me.MAY BE it is worth a try.
I tried also sand from crushed rock.It is more fertile(it was a granitic stone) but makes a crust very easily so not to be used on the surface.For a second try, I used a 0.5mm sieve and kept only the 0.5-2mm part.The result was very good.

[Tim Ingram]

Paul - it's time we made a visit to see the new crevice garden! At least we are quite close. Your figure of 60% germination rate from different pots is pretty good I think. From memory Peter Erskine quoted around 50% and I imagine that would tie in with many growers experience (although depending very much on what is being sown). With your own collected seed it could go a good bit higher. How much self-sowing is likely to occur in a crevice garden? A few things self-sow on my sand bed, notably Polygala calcarea and Centaurium scilloides, and Aquilegias (too much!) and over time this could result in a lovely natural effect.

When I mentioned crevice gardening on the AGS website, John Good made a comment about the soil used in the crevices, suggesting that sand was likely to dry out quite badly. In ZZ's booklet he talks about using quite heavy loam, even clay. Are the plants in pure sand or is there also loam incorporated?

[Maggi Young]

In IRG 14, of February 2011, there is an article from Harvey Wrightman in Canada of his "recipe" for making crevice gardens in a trough... he uses a sort of clay sandwich:  http://www.srgc.org.uk/logs/logdir/2011Feb241298591020IRG14_Feb_2011.pdf

[Tim Ingram]

Maggi - very many thanks for pointing me to IRG 14; there is some really excellent advice there. The Irish connections were interesting too having visited several gardens over there. Pulsatilla ambigua looks very beautiful even for a Pulsatilla!

[henkw]

Wisley crevice garden 07-07-2011

[henkw]

Wisley Crevice Garden 07-07-2011

[henkw]

Wisley Crevice Garden 07-07-2011

[astragalus]

Lesley, the sand I use in my crevice garden is quite coarse with small gravels.  It's what you have before it's sieved yet again for mason's sand.  I find that mason's sand is much too fine and uniform and will form a crust.  The sand I use doesn't do that at all.  It's also the sand they use on the roads here for the winter (I get it before salt is added) and has the added benefit of being very cheap.