Stone mulch

[r2pi]

Hi,

Quick question.

Is it OK to use crushed rock "toppings" as a mulch in pots of Trichocereus cacti?

I have some left over from some landscaping, was about to use them and then wondered whether all the fine powder in amongst them might overdose the plants on soluble minerals? (After all rock dust is used as a fertiliser) FWIW it looks like crushed sedimentary rock of some sort with particles of all sizes right down to a large amount of fine chalk/clay-like dust.

[PhoenixSon]

i would, as i use dolomite once in a while other rock materials would add other goodies to your graden bed so i dont see why not. Normally it takes a long while for these minerals before they are available to the plant to be absorbed. Very long term fetilizers rocks n such thats why i like them so much. Even when i see concrete blcoks with rocks through them i picl them up to add to the cactus garden. Any rocks i can collect i do.

[Foo]

just wash the rocks. Should be fine, ive used broken plates before.

[Evil Genius]

Get yourself some Quartz Stones. I use them for all my pots now as they protect the seedlings/plants from algae, fungal infections and all kind of shit. I use very small particle quartz stones for my sowing-containers too and since i do that, i hardly lose seedlings anymore.

[flumsquid]

i wouldnt,

IME sedimentary dust will eventually tighten the soil mix.

cacti roots need voids in soil to breathe.

if you wash all the dust out you'll be sweet.

[Evil Genius]

Dont know the exact structure or composition of "Rock Dust" but flumsquid pointed out correctly that very fine mineralistic powder/soil tends to clump very badly. Besides, it does NOT protect the plant from fungus and algae as the particle size is not big enough.

I use something like this:

It is big enough to keep away all kind of weeds and algae, protects the roots and does not clump.

[IndianDreaming]

@EG - Do you mix the stones in with the soil? Or do you just put about 1cm or so in the surface? Is the MM up the top the scale for 1mm? Stone size of 1-2mm?

[Evil Genius]

Not mixing anything with the stones. Pure Quart Stones. I use mainly minderalistic soil plus some additives as basic soil and put the stones on top of it. For freshly germinated seedlings i use smaller sized stones, 1mm in diameter. For the larger ones i take 2-3 mm and above. Its pure magic as it improves success rate tremendeously! All good cactus nurseries do that.

Btw Nitrogen, thats the seedlings from last years seed! ;)

Edited October 5, 2012 by Evil Genius

[Foo]

wow i picture of EG's cactus,

Is it a blue moon or something

[Evil Genius]

Is it a blue moon or something

lol yeah, i rarely give insight into my mad scientist cactus collection. But also because i had a too bad camera. Finally got me a good smartphone that comes with a good camera so will change that now.

[GoOnThen]

EG are you top dressing with the stones after germination or before.

Cheers

Got

[Evil Genius]

After because cacti need light to germinate but as soon as seedlings come up, i sprinkle them withz very fine quart stones. The seedlings will find their way to the light. You can help them a bit to avoid some of them being trapped under stones but generally speaking, the covering will reduce losses to an absolute minimum, even if you may lose a few because of the stones. Its nothing compared to not having a covering layer on top as this makes it possible for you to water more without getting problems with moss and algae.

[Mr. Bowser]

I've never used the quartz stones, usually just sieve out the 1-2 mm pieces out of play sand because I'm cheap. I sprinkle this over top of the seedling soil immediately after sowing. (trying to sow directly onto a layer of grit is a PITA!) I shoot for a thin layer about 1 mm thick (can still see about half the seeds through the grit). After they all germ, then sprinkle a bit more. Like EG said, the difference is amazing. Keeps that cobweb mold stuff to a minimum, and makes it easy to remove if you get any.