You CAN substitute, but Perlite holds considerably more water than granite, so you'd need to decrease the Turface fraction and increase the perlite. I know that sounds counter-intuitive, but Turface holds more water than perlite, so by decreasing the Turface and increasing the perlite, you'll be reducing water retention to approximately what the gritty mix would be.
Maybe
3 parts bark
4 parts perlite
2 parts Turface

The granite would still be better, though. Where do you live? I might be able to help with finding the granite or a suitable substitute through one of my many bonsai contacts. It would help if you included your USDA zone and state in your user info (like mine > z5b-6a MI).

Al

briana,
I am glad that your (continued) question(s) have been answered.

The GW/FF does not permit editing.
It also forbids (rejects) a "quick" follow up post
by the same member in the same thread.

One general advice to (future) avioding 2 threads on the same subject:

One way around this, is to "re-post" with a (slightly)
different subject tittle, e.g.,
Question for Al -> Question2 for Al

Here is another example of how I did a quick re-post,
(without getting the "Message Rejected" thing).
Note the "2-" in the subject tittle.
Having one (1) tread on a subject is desired by all,
and is also suggested by GW.
We all live and learn...

Hey Al, I have access to and have the 3 gritty mix ingredients. Last year it worked for me but I just potted up 3 trees and my back is shot! I have a good source for coarse perlite that is less expensive than the grani grit or the turface. I see you recommend 3-4-3 Bark-perlite-turface as a substitute but you say "the granite would still be better though". Could you explain further? Also the turface is so much finer than the perlite or grani-grit that I wonder if it is in any way detrimental due to its fine texture. Thanks for your thorough explanations.

Hi All -

Thanks for all the help, I really appreciate it.

Al - I am in the Saint Louis area.

I will need to look up my zone and modify the account to include this information.

Thanks again to everyone.
Brian

Ejp - I like the extra weight of the granite because it helps eliminate blow-overs, I also don't have to screen it because it's prescreened. It works perfectly (for me and for most types of trees) at equal parts of all 3 ingredients, but the stark difference in water retention between the Turface and granite allows me to easily adjust water retention by increasing one or the other just a little while I go the opposite direction with the other, all the while keeping the bark fraction at 1/3 or less. More T and less G = more water retention - less T and more G = less water retention. You lose some of that adjustability by substituting perlite. Perlite also tends to float to the top. Try to get perlite that is medium in size - around 1/8" so it stays in the mix better if you use it. It helps to rinse perlite for plants that are sensitive to fluoride, too. (I don't know - so don't bother asking). Lol

Brian - you're very welcome. Hopefully, you can locate the granite near you. Shipping would be outa sight. You might be able to find cherrystone, too. It's mined in MN so I can see it coming down the river on a barge? Rural feed stores or elevators are the places to call.

Al

Hi All -

Al - I am happy b/c I believe I have found a local source for the granite (farm and feed atore - thanks for the suggestion!)
The place I called has 2 sizes available that are used with young and older chicks -- he said one is course sand size and the other is more like a small pebble. I will print the picture of your example and will have a look this weekend.

I am trying to find the pine bark fines - a nursery I have talked to here will have ~3/8 inch fines, which I believe is still a bit too large but is better than what I have. I believe the upper size limit is 1/8 inch?

Again,thanks for everyones help!
Brian

If you're making the gritty mix, the 'ideal' bark size would be 1/8-1/4". I buy a Shasta Forest Products product (white fir bark) that is clean & prescreened in that size. I bought 20 - 3 cu ft bags in CHI last summer, so I have enough to last awhile, but all my friends keep moochin'. ;o)

I always used Gran-I-Grit in 'grower size' for the granite fraction, but in recent years I've gone to #2 cherrystone, which I prefer, but only because it's a rusty color and looks better in my bonsai soils. Performance is the same.

I don't know if the link to my Yellow Pages search will work or not. If it doesn't, just go to the Yellow Pages & enter the search words St Louis MO feed grain and you'll have lots of leads for the granite or cherrystone.

Al

Here is a link that might be useful: Yellow Pages search

If weight is a determining factor, Perlite could be substituted for the expanded shale.

~james