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Substituting granite in gritty mix

Posted by fortyonenorth NW Indiana 6b (My Page) on
Thu, Nov 10, 11 at 12:08

I've had very good success using the 5:1:1 mix for raised planters and a variation of the gritty mix in my small containers. I recently acquired a reasonably large Japanese maple (7-10 gal) and I'm reluctant to use the straight gritty mix for the re-pot. I'd like to substitute the granite portion and I'm looking for advice. In a older post, Al suggested that the pine bark has drainage/water retention properties which approximates an average between the Turface and granite. With that in mind could I simply leave out the granite and increase the % of pine bark or would I need to add perlite or something similar to maintain adequate drainage.

My reasoning is this: the native soil on our property is pure sand and, when it comes time to recycle the mix, I don't want to add granite to my garden beds. I've considered using the 5:1:1 (this won't be the permanent home for the maple) but I really like the qualities of Turface. My sandy (very low CEC) raised beds can't get enough of it.

Thanks in advance!

Follow-Up Postings:

RE: Substituting granite in gritty mix

i have made the 5.1.1 with pine bark fines, turface, and perlite with great success. That sounds like what you are about to do.


RE: Substituting granite in gritty mix

I've been using pumice in place of the granite, in both gritty mixes. I wanted a little more water retention because of all the drying winds here on the coast, it doesn't break down and still helps to keep things open. Perlite dumped in the yard blows around.


RE: Substituting granite in gritty mix

Thanks for the replies. I've done some more reading and found, in a post by Al, a suggestion to use additional Turface when omitting the granite:

"Are you also going to use crushed granite in the soil? The 1:1:1 is uncomposted pine bark: Turface: crushed granite grit. If not, you should use 2 parts Turface or calcined DE and 1 part bark and screen the Turface or DE through a kitchen strainer with holes about the size of insect screen."

Thought this was interesting as it would seem to create a soil that is more water-retentive than the standard 1:1:1 mix. Any thoughts?

RE: Substituting granite in gritty mix

What was the context for that posting by Al?


RE: Substituting granite in gritty mix

It was in this thread here - about 1/2 way down the page.

Here is a link that might be useful: 100% Turface

RE: Substituting granite in gritty mix

When I make my medium mixes, I take into consideration where the container will be kept... as in what kind of environment it will be situated in. If it's for an outdoor container, I like a little more moisture retention because of the drying winds we get, combined with the heat of summer sun in my area. I also take into consideration the size of the pot, and any other variables that might affect moisture retention and evaporation. In short, I don't want to have to water more than once daily... just in case I can't be there to water for part of a day.

I keep my larger Japanese Maple specimens in a cross between the 511 and the gritty mix.

I'm sure that not much of what I'm saying will be usable to you... except that it helps me considerably to think about all the variables my containerized plant is likely to encounter through its growing season, which helps me decide on materials and ratios used in a particular mix.

The fir bark is the mainstay... with perlite, granite chips, turface, peat, aliflor, and a few other ingredients to choose from. I tend to mix my mediums in small batches for the individual plant. Once you've been using this general type of a medium for a while, you get a feel for what mixture will work best for the plant you have in mind.

Al and Josh always offer sound advice... you can't go wrong with their recommendations.

RE: Substituting granite in gritty mix

Thanks for the reply, Jodik. I ended up taking the gritty mix I had on hand (1:1:1) and mixing it 50/50 with pine bark. I guess that gives me about a 4:1:1 mix of pb:turface:granite. It's very free draining, but we'll see how that does for the winter. The maple was semi-bareroot, so I had to do something immediately, but I may re-pot in the Spring if I feel it's necessary.

RE: Substituting granite in gritty mix

When I first began using the grittier mediums, I made the mistake of not pre-moistening the mix before planting in it. Let's just say I had some issues... very stressed plants! Now I know better, and everything goes smoothly. But there was a slight learning curve when I first started using these mixes.

I think the important things to remember are how the mediums work, and why they work. Once you understand the purpose of a medium, and the basics of what containerized plants really require... understanding what happens under the soil surface at the root zone... it's all relatively easy from there.

And even if you do have questions or issues, there are plenty of folks here using the same mediums, so help is always available.

Happy Growing!

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