The problem I see with such a mix is that it has 'too much' drainage - there is little to hold in nutrients. Water, and disoved nutrients, will pretty much run right thru that with little remaining in the pot for the plant to absorb, I believe.

I guess you could test this out with a plant that you could afford to have grow less well and see what works, and experiment with how often you would have to water and fertilize.

Are you wanting to grow a bonsai fig plant? :) I like mine big enough to get fruit from.....

Seriously, I understand the reasoning, no one likes the idea of having to repot a plant if the media deteriorates in time. Like I said, feel free to experiment with it, and please let us know if this works for you. We would love to hear about successes and new methods that have advantages.

You can grow any plant in a suitable bonsai type mix. The goal does not have to be a bonsai. Bonsai literally just means 'plant in a pot'. The choice of soil does not make it a bonsai. I have many plants in bonsai mix even though they are not meant to be end up as a bonsai (in the japanese sense)

As mblan said you can use all inorganic materials for soil and that soil will hold up for a long time. But you still will need to repot or up-pot at some point. I have used mixes of:

• grit and turface
• grit and pumice
• lava rock and pumice (for more water retention)

You could use perlite too and will make it lighter. Sift it to approximately the same size as grit and turface (1/8-1/4). You can do 1:1:1. If the plants needs more water - like most tropicals then up the turface and/or perlite. Both turface and perlite will hold nutrients - just not good as bark and peat. So you will have to fertilize more often or you can be lazy like me. I mix half dose of controlled release fertilizer like Osmocote (for perennials) in the soil mix. This is to account for times when I just do not have the time to use liquid fertilizer or raining too much.

There is a commercial product too - Lechuza Pon I think is the name. From Germany. Or check Bonsai Boy for premixed ones.

Some years back forum member Tapla posted a 5 -1-1 gritty mix here. Perhaps a search may turn up some information about it.

Good luck

Martin

The 5-1-1 and the gritty mix are not the same. And neither are entirely 100% mineral based and permanently durable. As TofC noted, the mix will breakdown at some point and will need to be replaced.

Personally, for anything larger than a bonsai I would not recommend a 100% mineral based soil mix as it will simply be too heavy to manage well and require much too frequent watering (in high heat, often multiple times a day!). I use the 5-1-1 or a modified formulation for everything in containers other than my cacti and succulents. I only need to repot/refresh the soil every 3 years or so and that's when the plants typically require root pruning as well.

Thanks everyone for comments. I am planning to grow trees for fruit production. I mainly wanted to go the mineral mix route because it is so difficult to find pine bark fines that are in a suitable size to use, I find that if I buy the bark available here at the big box stores - either 2 or 3 cubic feet bag - after I screen it to 1/8 to 1/4 inch i can probably use about 1/4 of the bag. I have experimented with putting the large chunks for a short time in a blender which seems to work but is time consuming. I may have to for experimental purposes just throw away the bark I can't use (or give away to a landscape guy here) since the bags are only a few dollars and use what I have to make a mix to try out for next spring. The 5-1-1 takes a lot of bark for the size and number of pots that I have - at least I read it is possible to get up to 2 or 3 seasons use from the mix before needing to replace, Either that or I need to find an effective way to manage the PWT - maybe ballast as Tapla has discussed. If I put a layer of sand or something on the bottom and then a piece of landscape fabric and then a mix like pro mix HP will the capillaries within the landscape fabric serve to help pull excess water into the sand and out of the pot drainage holes? I had a colleague at work state that he put rocks at the bottom of a pot and burlap on top of that and then peat based soil on that and he claimed the small fig plant I gave him grow like a weed in it, The tree was quite small when I gave it to him and he indicated it grew quite a bit in one season.

Thanks!

Brian

Ballast works when the same soil mix (or very similar mix) spans from the bottom to the rest of the pot. Ballast just takes up space near the bottom of the pot where PWT is present and effectively reduces the volume of saturated soil. Suitable ballast material could be inverted pots, styrofoam biggish rocks, etc.

Sand will hold a lot of water and thus will be counter productive. It is composed of fine particles and has high PWT. So effectively it will be like soil sitting on water.

Rocks are opposite and effectively it is like soil sitting on air very similar to just a pot without rocks. But rocks will just take up space, and the soil height will be less but the PWT will be the same. So does not help either. Now if the same soil mix were to fill the gaps between the rocks and reach the bottom of the pot then it will act like a proper ballast. So it is essential to have some gaps and that those gaps are filled with the mix.