I wouldn't go over 40% turface. Maybe start around 2:1.

I'd say about 2:1, grit:screened Turface, too. I think you might be operating on a faulty premise, though. Regardless of what size container you plant in, the planting is going to become rootbound and in need of repotting before the soil (with bark) outlives its useful life. The bark is an extender - something that has roughly the water retention of the average between grit and Turface and increases the volume while reducing bulk density. If you limit the bark fraction to no more than 1/3 of the whole, soil collapse shouldn't ever be an issue. The only scenario I can imagine where it might be is in an older planting that experiences root dieback, for some reason, involving a very large fraction of the roots.

Al

Hi Everyone -

Thanks for the replies.

Al --

I am still expecting to do root pruning.

I was just curious because of decreasing the amount of work required to remove the "spent" bark whenever that is (1 year, 2 years, ?) and replacing with new bark.

If the mixes would be equal in terms of growing plants (bark no bark) then I would never have to worry about replacing bark...I would only need to root prune when needed.

Is there something else I am missing in removing the bark fraction?

Also, the mix would be cheaper for me since I currently order the bark from Oak Hill Gardens (use the same as Al T uses) and pay about as much for shipping as for the bag of bark itself!

Thanks,
Brian

Brian: I understand what you are getting at. If you use only inorganic materials (Turface and granite) then theoretically you should never have to replace your soil-building materials. The only part of the gritty mix that will break down after a 2 or 3 seasons is the pine bark. If you eliminate the bark, then you should be able to reuse your Turface/granite mix for many years.

As you and Al both said, you will have to root prune every so often, but if you are willing to do that then I see no reason why your mix wouldn't work.

TYG

Interesting question: If Brian used screened diatomaceous earth (DE) instead of Turface in that mix would the ratio change at all?

If I recall correctly I believe Al said that DE holds a bit more water then Turface. If so, then a 2-1 mix of granite/DE would hold slightly more water than a 2-1 mix of granite Turface, correct?

Thanks.

TYG

That is correct, TYG :-)

Josh

Thanks Josh!

I'm trying out some DE now, a product called OptiSorb. Supposedly it's a great soil amendment. The bag contains a mixture of fine particles all the way up to 1/4", so I suppose it's similar to Turface.

I've not tried to create a soil mix out of 2 parts granite and 1 part DE, but I might have to try it as an experiment.

Thanks.

TYG

I've been growing in a turface/grit mix for several years now, with good results. I started with the mindset that if the bark has a moisture retention property averaging between the turface and grit, that a straight 50:50 mix would be about the same as gritty mix with bark. I've found that to be mostly true, and use the 50:50 ratio for plants that like a fair amount of moisture, notably tropicals. However, it holds too much moisture for plants like cacti and succulents that like drier conditions. That's where the 2:1 grit/turface, respectively, comes in. I've recently incorporated lava pebbles into my mix though, so I'm in the process of trying different ratios of each of the 3 ingredients.

As for having a completely inorganic mix, well, I love it. It can indeed be used forever, but there is some chunks of roots left in the mix after a repot, so I like to repot in fresh mix. I then let the old mix dry out, then run it through a piece of 1/4" mesh, which sifts out a lot of the root pieces. The best part is not having to remove every bit of old mix, so whatever pieces are lodged in between the roots can stay. I think the mix looks more ship-shape without the bark too, and loos even better with red lava rock mixed in. An additional note to mention too is that the absence of bark removes the hydrophobic properties of that come with it when left to dry, making watering easier.

Joe

Let us know how it goes, TYG!

Great points, Joe.

Josh