Gravel, grit, etc.

[fixpix]

I hope this is the right place to ask.
I am going to prepare some raised beds out in the garden (probably a few layers of old bricks around for walls) and I want to mix something in the soil to make it more alpine-like.
Problem is, I don't know what.
I know the English words, but I have no idea what exactly I can find around here.
Best is granite?
What size?
Can someone have a look at this site and suggest something?
Probably for mixing in the soil a size is good, and for "topping" another one?
I am gonna have a huge collection of Sempervivums (judging by the millions of seedlings I have now) and hopefully some Saxifraga and Sedum and Androsace and a few more.

And, what would be the approx. ratio? half garden soil and half such gravel/grit? Or it's too much grit?

Also... underneath the 20-30 cm of depth, should I put some kind of cloth, fabric to suppress any weeds?

OK. Here's one of the sites I found.
http://www.afacerist.ro/catalog/distribuitor_criblura/

As a note, they say this stuff is used for ASPHALT?

[David Nicholson]

I wouldn't class myself as the" fount of all knowledge" and others may contribute with other ideas. My suggestions would be:

For mixing with the soil 0-4mm, granite would be fine, and alpines like a really gritty, free draining, mix so too much grit isn't an issue. Your idea of 50/50 would be good in my view. For topping I would say 4-8mm and it might be worth sieving out the smaller particles of this and adding them to your soil mix. I'm not sure about your idea of weed suppressant fabric, I suppose if this was the type that allowed water to pass through it then it wouldn't be a bad idea but if it didn't allow water to pass don't do it as it would give you very bad drainage no matter how much grit you added to your soil. I would be as interested as you at any in any other views.

[pontus]

I have just been making raised beds for my chinese and japenese bulbs, so not for alpines, but what I did was buy wooden pre made raised beds which you build yourself, by interplacing as many planks of wood as you want untill you attain the height that you want. At the bottom i put plastic mesh to protect aghainst mice and field voles, and on the sides, I put what they call geotextile here, which is a black fabric that lets water pass through, to ensure that the planks do not rot in time.

The planks at the bottom where dug in 5 cm into the soil.

My soil mix may not be what you are looking for, but I used my normal woodland, humus rich mix, which consisted of aproximately :

30 % ericaceous acid soil
10 % normal garden soil
10% leaf mould
10 % perlite
10 % bark or wood chippings
20 % humus rich neutral soil with perlite already mixed in.
10 % pine needles

i then covered with a 2-3 cm thick layer of pine needles.

if i had had some, I would have incorporated a bit of sand and very fine granity grit as well..

Pontus

[fixpix]

Thank you both for the time you took  to reply.

Pontus, your mix sounds like something I would eat for dinner... that's how good (read: delicious) it sounds.
It would be too costly and "effortly" to create over here.

David's suggestions looks like the way to go. Easy and do-able.

BUT... i'd love to hear what others have to say

[Alan_b]

I don't know the right answer but I have been inspired by a talk I went to last year where the properties of various compost were demonstrated by putting some compost in a plant pot, pouring water on the top and seeing how long it took for the water to drain through.  So you can actually measure how free-draining your mixture is by timing how long it takes for a measured quantity of water to drain through it.

You might be able to do better than this by putting some of your mixture in an oven to bake out the water content then adding measured quantities of water and seeing how much drains through and how much is retained.  That way you would learn not only how rapidly the mixture drains but also its water-holding capacity.   

[fixpix]

Well, the thing is, we get really hot and DRY summers. At least that's how the last two were.
And I don't want to spend all my gardening time just watering with the can.
Experiments are fun... but I feel I don't have the time needed.
With only Saturdays for gardening (till days get longer) I rush into the garden to weed, take pics, enjoy...

[Alan_b]

Experiments are fun... but I feel I don't have the time needed.

But whatever you choose to fill your raised beds with will be an experiment in itself.  My suggestion was intended to give  quantitative results in a matter of hours.  You will make your choice and then get qualitative results in a few years.

[fixpix]

I found this. 4-8 mm. to me, that's large (to mix in with the garden soil).
But they say 0-4 is called "sand" now, i am afraid that's gonna be too small.
I guess I need to go and see.

[Maggi Young]

We use  6-8mm granite grit to mix in potting soil and in the garden if needed.

[Susan Band]

Hi
I wouldn't bother with the weed suppressant, most small weed will come from the surface and any really bad perennial weeds with runners etc will make there way through the ground cover. Make sure you get rid of any weeds that creep before you start. 
Adding some humus to the mix like Pontus suggests is a good idea as it holds some moisture doesn't stop the drainage qualities.
Good luck

[fixpix]

So Maggi, this size would be OK to mix in? For topping I thought it would be OK anyway.
Susan, I would if I could find such a thing around here.
Romania is still far behind in what gardening means. At gardening centers you can't even buy perlite or vermiculite.
They only sell normal mix for potted plants, some mix for cacti, and a few other mixes I can't remember.
We (as a family) only use well rotten cow manure cause well, we have a cow
The only weed I am really afraid of is some kind of thistle. While I was digging for the raised bed I could still find roots 30 cm down. I am not sure how deep I'd have to go.
And ... I need to comfort dad. It's actually his part of the garden and he is worried I will get tired of this alpine craze and later I will give this up and he won't be able to remove the rocks from the garden.
So I think by placing a layer of weed suppressant will make a barrier.
Surface weeds I am not worried about, I spend quite a lot of time weeding in different parts of my flower garden...

[Susan Band]

Start collecting weed free leaves and/or pine needles and make a pile of them. Too late for this project but they will come in handy for the future. You can't buy good humus here either you have to make your own. Adding a layer of dung occasionally to the pile will make good compost to mix in for woodland plants. You find here all good gardeners have a compost heap of some type. Keen gardeners are found in the countryside or town parks collecting alsorts for their special mix 
Susan

[pontus]

talking about collecting, today I went up the jura mountains again to my favourite spot to collect some more forest humus as well as dryer gravelly soil, gravel and also pine needles, rocks, logs...the pine needles soil and gravel in large 60 L bin bags... as i had just finished, and was on my way home, a forest guard unfortunately came along, looking very puzzled, and asked me what I was doing... I thought oh well this was and will be my last collecting trip!!! maybe police station next? or a fine? . I hesitatingly answered the truth : I was collecting pine needles to (amonghst other things) improve the drainage of my borders, and also add a bit of humus and grit...etc... so the plants will grow well...

at that point, the 2m tall man anwered back with a slight smile : "oh well, thats absolutely fine!, have a nice day! goodbye!"

quite amusing!

(he was patrolling the area he told me as previousely, people had been dumping their rubbish there...so he got alarmed when he saw all my huge bin bags!!)

Pontus

[fixpix]

Funny story Pontus...
Would have been even funnier if he had a nice alpine garden of his own, and start a nice friendship with many plant swaps!
And yes, I hate it when people just dump their rubbish in certain places, just because there are no houses around and people to see them.

[ruweiss]

We have a mixing station for asphalt near us and they use grit in different
grades and sand to produce it. Here I fill my material for the potting mixture
and topdressing in buckets and get it home by car.
This is maybe a suggestion for other rockgardeners, asphalt is used everywhere
for road construction.