Top dressing for succulents

[Paul in Essex]

All I can add to this is whatever top dressing you use, use one that you already include in your soil mix. Nothing worse than separating out decorative gravel when potting on.

Top tip!!

I recently switched over to using LECA as a compost ameliorant and top dressing. Not used it for long enough to be certain but so far it seems perfect.

[el48tel]

The best voidage is obtained by random sizes; uniform sizes give denser packing arrangements

I agree that if you carefully pack spheres ideally then even slightly different sized particles can substantially increase the gaps. But is that so for a mix were it is randomly dumped in? I thought these all turn out about 50/50 grit to air.
If you include notably finer ingredients they fit between the large ones and reduce the volume of air, I think particles less than about 1/3 of the basic diameter start to do that.
Welcome any corrections to my understanding!
Cheers
David Lambie
Bristol

You are not wrong - so a math project on ratios will be on the "to-do" list. But there are issues with the other components which can fall into the holes. Clay (cat litter) goes slimy; organics like peat hold a lot of water then go like concrete when dry (correct phrase because of the composition). So a top dressing like the non-ionic component (grit / sand) is the right idea because it allows the removal of the seedling without root loss but allowing the old compost mix to fall away. Been reading the papers written by the French & German growers and the composition of the seedling mix and the planting on mix are important in this respect.

[el48tel]

UPDATE
If the ratio is about 0.22 : 1 --------- then a small grit will fit in the void. larger than 0.22 is better because it opens the structure. smaller gives the chance of the void being blocked

[Nick_G]

Clay (cat litter) goes slimy;

You must be using the wrong stuff.

[el48tel]

Clay (cat litter) goes slimy;

You must be using the wrong stuff.

No I am not.

I don't use it. I am not convinced that the ions are not exchanged.

[MikeT]

Clay (cat litter) goes slimy

You must be using the wrong stuff.

I agree with Nick, the baked clay cat litter doesn't go slimy.
If you don't use it, el48tel, why do you think it goes slimy? Is this something that someone else has said?

[Herts Mike]

Clay (cat litter) goes slimy;

You must be using the wrong stuff.

No I am not.

I don't use it. I am not convinced that the ions are not exchanged.

Could you explain?

[conolady]

Clay (cat litter) goes slimy;

You must be using the wrong stuff.

No I am not.

I don't use it. I am not convinced that the ions are not exchanged.

The right stuff doesn't go slimy.

[el48tel]

Two points here
1. I had some plants from a plant sale which contained that which I am told was Seramis or similar and was told was similar to "cat litter". Washed the used compost to reclaim the grit / sand --- found I had a slimy stuff on the surface (same colour as the component we discuss) --- asked as a newbie at the local branch and was told in no uncertain terms of the origin. Similar tale from a bag of Westland Cactus compost bought last year when I was starting this hobby.
2. Without bragging or one-up-man-ship, I have a background in Chemistry and ceramics, and understand the nature and behaviour of clay based materials. Please tell me if I am incorrect in this statement, "Very few cacti and succulents grow in silt or kaolin". If I am incorrect I shall most definitely apologise for my error.

[Nick_G]

I grow all my cacti in pure cat litter, it doesn't go slimy.

I boil all my used cat litter for ten minutes to sterilise it before I re use it, it doesn't go slimy.

I have been doing this for many years now, it doesn't go slimy.