Al

Undoubtedly, the microporosity of the Turface granules contributes to the results obtained, but the extent of that contribution, under the conditions of the experiment, is difficult to determine, and as a first approximation I chose to ignore it. Perhaps a longer (how much longer?) period of saturation might have altered the results somewhat. Similarly for a longer period of drainage. As I understand it, one of the reason for using Turface is that it tends to retain water longer than some other media due to its microporosity. Presumably, some of this water is sequestered in the micropores, so that the pores are filled and don't contribute to the volume of airspace. I suspect that it might be difficult to determine the volume of the empty or dry airspaces and how much it actually contributes to the readily exchangeable air in the medium under the usual conditions of plant cultivation.

Ned (aka nemo2009)

I would expect those measurements to be closer to equal if the Turface was screened (through insect screen or a household strainer - about #10 mesh).

Al

Ned

We can extrapolate ...... if the particles were the same size, the air porosity of the Turface would be slightly higher than that of the granite, but would have the benefit of having much greater water retention because of it's internal (mostly) micro-porosity ...... which is what adds the feature of water retention adjustability to the soil as we +/- the volumes of Turface/grit.

Al

BTW, may I pick your brain on another related subject? My plan is to water daily with 1/4 strength Foliage-Pro. Do you think that's overkill (or underkill)? And what should I be looking for to evaluate it? I like the idea of daily waterings because it gets me out every day to see how the little rascals are doing.

Ned

I don't think the 1/4 strength FP would be overkill, but you may find that the daily watering might be (perhaps even if only at times), depending of course on the ratio of Turface:granite you settle on.

I evaluate plants by observing mainly what's happening with older leaves. Because N is mobile in the plant, older leaves are usually robbed of their N content, turn chlorotic as nutrients are translocated to support new growth, and then shed. Being familiar with how the plant breaks laterally is also a valuable tool. If the plant exhibits long growth absent of laterals, it's a good sign the N supply is insufficient. On the other side of the coin is too much fertilizer, which would manifest itself in burned leaf tips and/or leaf margins - sometimes holes in leaves that are obviously not insect damage. Under/over-watering symptoms are apt to be similar though, and can confuse the evaluations.

Al

I, myself, am somewhere in the middle, trying to find a good balance of medium ingredients, fertilizing frequency, and watering schedule... but I'm making good headway! My bulbs seem to appreciate the porous medium, and I've been going with a half-strength feeding schedule, with the addition of micro-nutrients at the same strength. Once I get a good feel for the moisture retention, and when I need to water, I'll be happy.

I'm getting there! :-)

I really have never found a plant in any growth phase that hasn't responded extremely well to having its feet in the gritty mix - or the 5:1:1 mix, for that matter. Honestly - I didn't say that to toot my own horn, because what I'm really touting isn't 'my' mixes .... rather, any highly aerated and durable mix you might come up with.

That said, I realize you know the journey itself is a labour of love and in some cases, more than half the fun. Your reference to 'patience' is something that brings a reflective smile to the bonsai practitioner who knows it intimately by default. Not always, but often, we might start with a piece of plant material, sometimes with a vision, and sometimes only knowing the species itself has good potential as a bonsai subject. 10-15 years later, after all those years of nurturing and development, we might finally be getting close to completing the vision we had way back when, or finally bringing what was once only raw potential to fruition. Have you considered exploring the world of bonsai?

Al

Ned

According to them, the ideal ratio is 50% solids, 25% air, and 25% water (this is for golf course turf).
Then they go on to list some combinations of these ratios of native soils before and after mixing in 20% of turface.

Of course, my observations dealt only with the airspaces, and say nothing about the water-holding capacity of Turface, which is largely a function of its microporosity--a point that Al has raised.

Incidentally, another property of Turface which I'll be looking at this morning is what I'll call its "friability", that is, its tendency to disaggregate after compression. I liken it to that similar property of rich, loamy soil that we all love. Dry Turface, like dry sand, won't stay in a compressed ball if we try to squeeze it in our fist. But add a certain amount of water, and the sand or Turface will remain aggregated. I'd like to know just how much water (volume/volume) it takes for Turface to just begin to retain aggregation. What possible usefulness this datum might have for container growers (or anybody else, for that matter), I have no idea. I guess I'm just trying to become familiar with the medium.

Now that I've gained a considerable amount of insight into mediums and the like, one size does fit all... I can successfully use Al's Mix for any of my plants, cuttings, seeds... and they grow!

My main plant of choice is the tender amaryllid. I collect and grow bulbs from all over the world... South Africa, South America, native species, etc... I've got a "jungle" going on indoors!

I think the turning point for me was when I learned the difference between container gardening and "garden" gardening, and I learned about the relationship between all the things that comprise a potted plant... the medium, the water, the root system, the fertilizer. The how and why of potted plants are so important to know...

There will be variables... not every growing environment will be the same, and climates and micro-climates differ. The amount of time and energy a gardener puts in will be different... etc...

The key, I think, is learning the how and the why, and having a little patience. Oh... and always being open to new ideas and to learning.

Although the above conclusion is hardly earth-shaking, surprising, or even useful, while I was collecting the information I did have a chance to think about a situation in which the ratio of water to Turface might be critical. When dahlia tubers are stored for the winter, two dangers are to be avoided: if the storage medium (often vermiculite, or cedar shavings, are recommended) is too damp, there is the likelihood of the tubers rotting; if the medium is too dry then the tubers may dry out and shrivel up. The medium must be that Goldilocks criterion of "not too damp and not too dry, but just right." I never found that instruction too helpful. How much better the instruction would be if it said "one cup of water to each eight cups of (some specified) medium."
Which is the ratio I will use this winter, substituting Turface for vermiculite, based on my observation of the water:Turface mixture.

Ned