There are always going to be trade-offs when it comes to deciding between grower convenience and maximizing vitality. It's not going to do much good to use a soil that requires watering twice each day, yet has the potential of maximizing your plants' vitality when you can only water once per day.

In the highly organic, peat-based soils most of you are using, water retention is determined primarily by how small the soil particulates are. Using peat-based soils extends watering intervals, but it also cuts down on aeration, which may or may not be much of an issue. I don't want to get too deep into specifics about different media unless there are questions, but when soils support perched water and the watering intervals are greater than a couple of days, there is some cyclic death and regeneration of roots going on. The fine hair roots succumb quickly to anaerobic (airless) conditions, some dying after only a few hours in saturated soil. If you water in sips to avoid the possibility of soggy soils, you get a build-up of soluble salts from fertilizer solution and dissolved solids in tap water, which brings it's own issues. When favorable aeration returns to the soil, the tree uses valuable energy to regenerate the lost roots, energy which otherwise would have gone into producing foliage, fruit, or other biomass, or would have been stored in cambial tissues and roots for future plant use. This is extremely expensive in terms of energy outlay and represents a considerable hindrance to the tree growing at genetic potential. It is, along with plants growing under root bound conditions, one of the primary reasons plants in containers grow much more slowly than plants in the ground.

They way I work around the issue is to use a 2/3 inorganic medium that is adjustable for water retention.

{{gwi:1295}}

It consists of equal parts by volume of

1/8 - 1/4 pine or fir bark
Screened Turface (high-fired clay - almost a ceramic)
crushed granite (poultry grit in grower size or #2 cherrystone)

The soil particles are large enough that it holds no perched water. The bark has good water retention and the Turface has excellent water retention as well as a very good CEC. The soil is adjustable for water retention by varying the amounts of Turface and granite while keeping the bark fraction at no more than 1/3 of the whole. I have around 300 trees in it, and there are 100s of people from GW using it with excellent results. I use it for all my woody material and houseplants, including cacti and succulents.

Al

Hi Al,

Please bear with me on this. Does the mix you showed in your picture get mixed with any real dirt, or are you saying that it is solely what you use for potting a plant? Just want to make sure I'm understanding what you are telling me.

Thanks,

noss

I have been using the soil pictured, as pictured (no other ingredients other than gypsum as a Ca source), for more than 20 years. To get a feel for how well the soil is received here on GW, and so you don't have to take my word alone, just do a general search for "gritty mix", or go over to the container forum and simply start a thread asking for the assessment of the many using it.

You might find this thread (see link) about soils for container culture helpful. It's been active since '05 and has more than 1,500 posts to it.

Al

Here is a link that might be useful: Soils in more depth.

Al,

Thanks for the clarification and the link to the container forum post. I'll surely give it a try. Not sure if I can get the components for it here, but will call around and see. I don't want to bake my trees, or drown them, either. Though I can't see how anything could live in that mix, I accept that things must be able to do so! How fascinating. My curiosity is really piqued now. :)

noss

Because of its tremendous air porosity, it provides an extremely healthy environment for roots. Happy roots = happy plants and there is no opportunity for a healthy plant with a compromised root system.

Here is a tree I grew from a cutting and recently lifted from one of my nursery beds. It's a Japanese snowbell destined to become a beautiful bonsai (because of the fantastic roots) in a few years. I'm showing this pic because it is such a good picture of a tree in the soil.

{{gwi:7488}}

Another kind of fig (Ficus nerifolia/salicifolia - aka willow leaf aka narrow leaf fig) - the strings are securing it to the pot because it was recently repotted. It is badly overgrown, but I don't prune the top until I'm sure it is fully back on track after repotting:
{{gwi:3269}}

Another fig (Ficus benjamina sp.) in training:
{{gwi:78588}}

I probably have at least a dozen species of figs in addition to my caricas in the gritty mix. I also have trees too large for one man to carry in the same soil.

Al

Great pictures. I'm going to see if I can get the material and dig some of the potting soil out of the box with one of the figs and see how it does--If I can get the material. What do I feed the figs in that kind of soil, though? And how often? How often would the tree need to be watered/fed? It is really hot down here and it doesn't let up. Would this soil tend to get hotter than potting soils?

You're in Michigan; I'm in Louisiana and it's very hot and very humid much of the time, here. The sun is unbelievably strong, more so than up that way. Closer to the Equator.

When we visit family in NJ and head toward home, we can feel the stronger penetration of the sun's rays through the car window glass when we hit Alabama and then get onto I-10, turning Westward toward Louisiana, even in November, down here. I'm not trying to argue with you--Just to let you know my concerns. I will also go to the container forum and ask about this and perhaps the people who use your soil mix will be able to let me know how it works for them.

Thanks,

noss

I use Ultimate Potting Mix. When I am rooting cuttings I use a 50% perlite and 50% UPM. When they are bigger I use 100% UPM. It works pretty good in my hot climate.

If you're going to change to this soil, you'll want to wait until your trees are dormant and do a full repot, which includes bare-rooting and root pruning. It's problematic to have two markedly dissimilar soils in the same container. Don't get too far ahead of yourself. It's good to know why things work, so you don't have to just take my word that they do.

I fertilize almost all my trees with Foliage-Pro 9-3-6 fertilizer. It has all the essential nutrients in the right NPK ratio and in a favorable ratio to each other - an important consideration, especially in containers. A close second to the 9-3-6 would be Miracle-Gro 24-8-16 or 12-4-8. You'll notice these are all 3:1:2 RATIO fertilizers. This ratio is about as close as you can get to the ratio in which your trees actually use nutrients. This allows you to keep the level of EC/TDS (basically the level of soluble salts) in the soil solution at the lowest level possible w/o there being nutritional deficiencies. This is a considerable benefit to your plants because it makes it easier for them to absorb water and the nutrients dissolved in the water.

You'll be feeding with low doses every other week, on a weekly basis, or every time you water. It's up to you. More on that after you decide you'll be using the soil.

The soil won't get hotter than other soils. It will actually remain cooler because it has much better gas exchange and will get some additional cooling from evaporation. I have friends in TX, FL, SO CA using the soil with great results, so there is no reason you can't use it anywhere you wish. If you're worried about water retention ..... remember it's adjustable by varying the amount of Turface and grit.

Please do inquire at the Container Forum. Lol - actually, there is a post there now from a person concerned because he felt the soil might have too much water retention. He was just watering too often.

Al

About that getting ahead of yourself thing: when you decide to make the soil, you'll be adding a little gypsum to it as a Ca source. This means that to keep the Ca:Mg ratio in balance, you'll need to add a little Epsom salts (MgSO4) to your fertilizer solution each time you fertilize. I'll go over that again if you need me to when you're ready to pot into the new soil. No sense in worrying about it until then.

Hello loslunasfarms, I'll see if I can get that Ultimate Potting Mix--Is that Fertilome? I need to condition my in-ground soil and something like that would probably help with that, as well. We have clay here, no sand and very little organic material. The soil can get compacted very easily. When it dries out, it's like brick to walk on. My boxer accidentally pulled me down and I hit the grass flat. It had been dry and that was a hard landing. I had to lie there a few minutes to assess if there was any damage. Wish there was a way to loosen up the soil under the grass. Don't know of one. Is there a grass/soil forum? Will have to look see.

Hi Al, I'll wait until dormancy, thanks for the admonition not to get ahead of myself. :) I can always learn from people who are experienced. How interesting! The person was concerned about too much water retention from the same soil I was concerned about not enough of it.
I'm printing out all good answers and keeping them for reference even though I would have the forum to use as reference. If I'm going to keep some of the trees in containers, then I want them to do well. I'll be needing your input about the Ca:Mg, etc.

Thanks again,

noss