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Where to buy "coarse grit"?

Posted: Wed Feb 23, 2011 5:41 am
by Lair3514
Some of my attempts to coax cuttings to root haven't been successful. In this case, I'm working with very small growing tips (approx. 1.5") that I salvaged from a couple of Harrisia jusbertii cuttings that were going downhill. I found this advice online:

Once the callus forms, the cutting may be inserted into a container filled with firmed cactus potting mix topped with a surface layer of coarse grit.

Where does one buy coarse grit? I had no luck at Home Depot Garden Center. If I can't find coarse grit, is there something similar that will serve the same purpose?


Posted: Wed Feb 23, 2011 6:18 am
by Peterthecactusguy
you might try the NAPA stuff as a substitute. I use a brand that comes from Autozone that is called Marathon. It has larger grain sizes then some of them which are more like dust.
I use that in my standard cactus mix. :)
Then again I am no expert, but all my cuttings are doing quite well mixed in with the stuff. (It's also called Diatomaceous Earth, which basically means it's smashed up Diatoms which are fossilized)

Posted: Wed Feb 23, 2011 1:36 pm
by Tony
Its expensive but you could try aquairum gravel.
They sell it in different sizes. Some pet stores might even have it in bulk for much less than the bagged stuff.

Or try the building materials places that sell block wall and stone masonry supplys, they usualy have all kinds of good stuff.

I also like to make my own. Its free, just alot more work.
River beds and washes are a great place to find alot of the right stuff, you just need something to grade it to the sizes you want and your all set.

Posted: Wed Feb 23, 2011 1:50 pm
by iann
Decomposed granite should be available in your area. Or any non-limestone gravel at about quarter inch size. Or for that matter, you don't have to put anything on top at all, but then your soil will dry out much faster.

Posted: Wed Feb 23, 2011 4:14 pm
by bett
Aquarium gravel tends to be coated in some resin mixture to prevent minerals from leaching into the water. Not really all that great for aquariums, so it's probably not worth putting in pots either. Plus it's way too expensive for what you're getting.
Try a farm supply store if you have one around. They usually have bags of poultry grit. You should be able to find 100% granite grit, though some mixes might have crushed oyster shell or other things mixed in so read the labels. Like the others suggested though, building supply grit might be the best choice. It'll probably be cheaper too. If you have a stone processing center somewhere that sells different grades of crushed gravel, you can probably go there with a small bucket and ask if you can buy a few pounds worth of sand. They might just give it to you for free.

Posted: Wed Feb 23, 2011 4:38 pm
by CoronaCactus
Roofing supply yards are a good bet, especially those that quarry their own. Not necessarily the retail stores, but the yards those stores get it from.

Pumice will also work.

Posted: Thu Feb 24, 2011 4:40 am
by TimN
Um, you live in Tucson, right? That place is littered with coarse grit!

I go out a few times a year and find a nice dry stream bed and get a few buckets of grit. I have three screens; one coarse (1/2" holes) to take out the big rocks, one medium (1/4" holes), and one strainer with 1/16th" holes.

Anything that stays on top of the 1/4" screen is used for top dressing. I then put what falls through in a big bucket of water and sift the sand out. So I wind up with top dressing, coarse grit (which I also use for top dressing) and sand. I usually just toss the sand in the yard or over the fence.

Doesn't cost much, but it's kind of labor intensive.

I wash everything well and spread it out on my patio to dry. I've got to keep an eye on it because my cats thing it's for them to poop on.

Once it's dry I put it in buckets and away we go!

I also use a product called TurfaceMVP that should be available in local irrigation stores. Ewing Irrigation is where I go. There should be at least one in Tucson. It's about $16 for 50 pounds. It's calcined clay and I use it and coir plus some other ingredients for my cactus mix.

The benefit of Turface is that it's lighter than coarse grit (not by a lot, but every little bit helps when your shelves start groaning! It's essentially the same as the oil absorbent other have mentioned.

Posted: Thu Feb 24, 2011 4:56 am
by Lair3514
Thanks for all the suggestions.

I called University of Arizona Cooperative Extension and talked to a master gardener about where to find coarse grit for use in rooting cactus cuttings. She said, "We don't recommend using that." She advised simply using soil with no coarse grit as top layer or as amendment.

Then I checked their web site version of the Master Gardener Manual under Cactus and Succulent Propagation. It advised using pumice.

Called a farm supply store and they have pigeon grit in 10# bag. The person I talked to said the grains looked about 1/8" or so.

I'm debating with myself whether to use 1/8" grit, pumice or soil only. I'll review the rooting processs again. Maybe last time I didn't keep cuttings out of direct sun light for a long enough period to get the roots established. That was probably my mistake, more so than the medium.

Re: Where to buy "coarse grit"?

Posted: Wed Mar 28, 2012 1:51 am
by jnspire
Pumice is good. You can also get just sand. The sand that I get for my mixes is called "play sand" and is used for children's sand boxes. The bag says that the sand is both sifted and washed. I figure if it's safe for kids it has gotta be safe for my cacti. It has worked Very well for me! :)

Often play sand is sold at Home Depot or Lowe's; but, because it is in a different department than the garden supplies most people don't find it. Good luck!

Re: Where to buy "coarse grit"?

Posted: Wed Mar 28, 2012 3:03 am
by hoteidoc
Actually, Jer, of all those, I personally would Not use play sand. Went thru that when i got started 3 yrs ago. Last summer I had some unexpected repotting to do :( on some of my earliest plants -- but learned a valuable lesson! I was amazed how compact the mixture had become, & how much coarser my ingredients had since become. Greatful to the plants that tolerated that mix! Any of the other recommendations are fine, pumice probably being the best if available. But if you use sand (which I do because I can get it very cheap :D ), get something coarse/gritty! Currently I'm mixing it with NAPA/Autozone(Fuller's/diatomaceous Earth) & @ 25% potting soil.

Re: Where to buy "coarse grit"?

Posted: Thu Mar 29, 2012 9:36 pm
by CactusFanDan
I have to agree that sand is a poor choice. It's all fine and dandy at first, but it doesn't have enough long-term stability to make a suitable potting medium. Using a lot of sand in a potting medium, you end up with the sand turning to what is essentially brick mortar in not very much time. Also, it gets moved around by water a lot and the small particles means that it will fill up air-gaps in your soil, which you have worked so hard to be sure to make in your soil mix. Using much courser aggregates is a better idea, as it helps to create more air gaps in the soil, which is what cactus roots enjoy (in cultivation moreso than the wild).

Aaaaaaanyway, back to the matter at hand. There are a number of things you can use instead of course grit, since course grit usually refers to granite or marble gravel, I think. Builder's merchants are a good place to look. A few good substitutes are:
-Expanded clay products (Hydroleca, LECA)
-Baked clay pellets
-Some kinds of cat litter (lightweight, dustfree, non-wood/wood pulp based)
-Aquarium gravel/river bed gravel
-Some kinds of very course sand

Hope that helps!! :)

Re: Where to buy "coarse grit"?

Posted: Fri Mar 30, 2012 1:10 am
by jnspire
Thanks for the correction! :)

I am sorry. That is good information though. I think I will continue to use it for my seedlings; but, move away from it as I repot my plants.

Re: Where to buy "coarse grit"?

Posted: Fri Mar 30, 2012 6:37 am
by Robinj
If you can't find perlit, is vermiculite a good replacement?

Re: Where to buy "coarse grit"?

Posted: Fri Mar 30, 2012 6:49 am
by Arjen
robin, yes it is, I personally think it's even better
zeolite works very well too!

Re: Where to buy "coarse grit"?

Posted: Fri Mar 30, 2012 7:28 am
by Robinj
Thanks strUKto.