I couldn,t see what part of the country you live, are the alpines hardy? andI believe alpines like an open well drained soil, when I did one in a big trough I mixed a lot of grit in the compost,

Some alpines cannot cope with our wet winters - it causes them to rot - because where they grow in the wild, they either have dry winters or are covered with snow. Some sort of cover to keep the rain off but still allow air to circulate underneath is all they need. I place sheets of glass stood on bricks over my alpines and they have all survived the winter

You say;

I sprinkled some horticultural grit and flecks of welsh slate on the surface

But did you put anything similar below them?

Perhaps the soil at the base of the plant/s is compacted and water is not seeping away, and the plants roots are sitting in water.

Its just a thought!

Do you mean gabion stone as I can't find any 'cabion stone'. Was this the mesh baskets/containers? If so there would be no soil just the stone whilst some alpines are perfectly happy growing in among rocks and scree they do need at least a pocket of soil to grow in. I'm not sure how you can supply this if you are referring to gabion stone baskets. Could you put up a photo so we can see exactly what you are referring to please.

Thanks to everyone who responded,the stone is what they put in the baskets not the baskets themselves it is granite they use known as cabion (italian word ) which means baskets.There is a mixture of compost and grit roughly 50/50 in the pockets created by laying the stones the alpines minus the pots were set in these so I don,t think drainage is the problem.Incidently I live near Saffron Walden in Essex.Perhaps they died because of the cold nights we had over winter one night in January I recorded minus 18.The only way I can protect them next time is I supposed to let them grow in the pots and remove them to over winter in a cold frame.I will try to take some photos of the rockery so you can see how it is set out, stay in touch for more info.

Our alpine plants survive outside in all weathers, unless we are wussing them for the show bench! I agree drainage is not the problem lack of growing medium to grow into is. I could give a huge talk/lecture on the needs of alpine plants but it really would not be appreciated and, frankly, it has already been written!

So, trying to understand what you are saying... you took these granitic stones and did what with the? Piled them into heap, dotted them around in an existing bed, tried to create a crevice bed with?

Sorry but to really help I need more info.

Dear Moon growe,I will try as I said before take some photos to give more idea of how I set out the rockery.I do appreciate any ideas, solutions to the problem.First off I bought about a ton of granite stone and set them on some weed suppressing membrene,one layer first covering the membrene about 10 foot wide between a lean to store for coal one side and decking at the other side.At one end it comes out 4 foot to reduce to 2 ft and out again in a sort of curving line to reduce back again at the other end against the decking.At the back is a 6ft fence running the entire width.It was then built up with another layer of rocks sometimes two or three thick so they wedged themselves together without tumbling over.This in turn made pockets in which to set the alpines.Incidently there is also a large water feature of 4 waterfalls at the back corner next to the coal store.The waterfalls are contained within the feature and not tumbling onto the rocks/alpines.It looks very natural minus some alpines which is what I am after.Hope this has explained it in more detail I will try and add photos tomorrow or Tuesday.

Is this rockery situated in full sun, or in shade?

Did you actually put any soil in with all the rocks? Just wedging the alpine plants into pockets where there is no existing soil is a recipe for disaster.

And what were the plants which did not survive?