At another forum site, I wrote the following because someone had asked if Scott's Premium Soil was a 'good' choice. You may find it of interest.
Is Soil X a Good Soil?
I think any discussion on this topic must largely center around the word "GOOD", and we can broaden the term 'good' so it also includes 'quality' or 'suitable', as in 'a quality or suitable soil'.
How do we determine if soil A or soil B is a good soil? and before we do that, we'd better decide if we are going to look at it from the plant's perspective or from the grower's perspective, because often there is a considerable amount of conflict to be found in the overlap - so much so that one can often be mutually exclusive of the other.
We know that grower A isn't happy unless he is squeezing every bit of potential from his plants, and grower Z isn't happy unless he can water his plants before leaving on a 2-week jaunt and still have a weeks worth of not having to water when he returns. Everyone else is somewhere between A and Z; with B, D, F, H, J, L, N, P, R, T, V, X, and Y either classically ignorant (it just means they're not aware there is a difference) or they understand but don't care.
I said all that to illustrate the futility in trying to establish any sort of standard as to what makes a good soil from the grower's perspective; but lets change our focus from the pointless to the possible.
We're only interested in the comparative degrees of good and better here. It would be presumptive to label any soil "best". 'Best I've found' or 'best I've used' CAN be useful for comparative purposes, but let's tackle 'good', then move on to 'better', and finally see what we can do about qualifying these descriptors so they can apply to all growers.
I would like to think that everyone would prefer to use a soil that can be described as 'good' from the plant's perspective. How do we determine what a plant wants? Surprisingly, we can use %s established by truly scientific studies that are widely accepted in the greenhouse and nursery trades to determine if a soil is good or not good - from the plant's perspective. Rather than use confusing numbers that mean nothing to the hobby grower, I can suggest that our standard for a good soil should be, at a minimum, that you can water that soil properly. That means, that at any time during the growth cycle, you can water your plantings to beyond the point of saturation (so excess water is draining from the pot) without the fear of root rot or compromised root function or metabolism due to (take your pick) too much water or too little air in the root zone.
I think it's very reasonable to withhold the comparative basic descriptor, 'GOOD', from soils that can't be watered properly without compromising root function, or worse. I also think anyone wishing to make the case from the plant's perspective that a soil that can't be watered to beyond saturation w/o compromising root health can be called 'good', is fighting UP logic hill.
So I contend that 'good' soils are soils we can water correctly, that is we can flush the soil when we water, without concern for compromising root health/function/metabolism/. If you ask yourself, "Can I water correctly if I use this soil?" and the answer is 'NO' ... it's not a good soil ... for the reasons stated above.
Can you water correctly using most of the bagged soils readily available? 'NO' I don't think I need to point to a conclusion.
What about 'BETTER'? Can we determine what might make a better soil? Yes, we can. If we start with a soil that meets the minimum standard of 'good', and improve either the physical and/or chemical properties of that soil, or make it last longer, then we have 'better'. Even if we cannot agree on how low we wish to set the bar for what constitutes 'good', we should be able to agree that any soil that reduces excess water retention, increases aeration, ensures increased potential for optimal root health, and lasts longer than soils that only meet some one's individual (and arbitrary) standard of 'good', is a 'better' soil.
All houseplants, unless grown from seed, have the genetic potential to be beautiful specimens. It's easy to say, and easy to see the absolute truth in the idea that if you give a plant everything it wants it will flourish and grow; after all, plants are programmed to grow just that way. Our growing skills are defined by our ability to give plants what they want. The better we are at it, the better our plants will grow. But we all know it's not that easy. Lifetimes are spent in careful study trying to determine just exactly what it is that plants want, to make them grow best.
Since this is a soil discussion, let's see what the plant wants from its soil. The plant wants a soil that contains in available form all the essential nutrients, in the ratio in at which the plant uses them, at a concentration high enough to prevent deficiencies yet low enough to make it easy to take up water (and the nutrients dissolved in the water). First and foremost, the plant wants a container soil that is evenly damp, not wet. Giving a plant what it wants, to flourish and grow, doesn't include a soil that is half soggy for a week before aeration returns to the entire soil mass, even if you only water in small sips. Plants might do 'ok' in some soils, but to actually flourish, like they are genetically programmed to do, they would need to be unencumbered by wet, soggy soils.
We become better growers by improving our ability to reduce the effects of or eliminate limiting factors, by clearing out those things that stand in the way of the plant reaching its genetic potential. Even if we are able to make every other factor that influences plant growth absolutely perfect, it could not make up for a substandard soil. For a plant to grow to its potential, every factor has to be perfect, including the soil. We'll never manage it, but the good news is that as we get closer, our plants will get better and better. It's that one little factor that we willingly or unwittingly overlook that limits us in our ability and our plants in their potential.
A 2-bit plant in a $10 soil has a future full of potential, where a $10 plant in a 2-bit soil has only a future filled with limitations. ~ Al
Al
