Let's get the dirt on soil.... What do you prefer?

Ok. I have noticed a theme that many plant woes are caused by the soil they are growing (or not) in. I would love to see a discussion that tolerates many different ideas with love. I know we have many people on here that dedicate their time to helping others learn to grow better plants. I absolutely enjoy seeing the different ideas, and I am insanely curious, so I will ask questions, lol.

As a secondary part, I got some pine mulch to use as a soil additive. It is partially composted so I didn't notice at first that it is not just bark, but also wood... What problems will this cause having used it as about 1/3 of the mix? I know it would be fine as an amendment outdoors, but not so sure about my fig and spath that I potted up. I basically need to know if I should go knock the new dirt off and repot or is this going to be okay?

I use whatever I have handy. Regular potting soil mixed with perlite, orchid bark, sphagnum...various combination's of those. I always lighten the store bought soil. Careful watering. I've got 150 houseplants that seem happy...except for the odd one that gets buried in a corner occasionally and doesn't get watered.

If the 'wood' parts of your mulch are pine sapwood or heartwood, the negatives will be fairly rapid decomposition (which will be dependent in part on the particle size - the smaller the more rapid the decomposition) and the nitrogen immobilization )tie-up) that accompanies the use of those products.

If the mulch also contains hardwood products or 'composted forest products', you'll have to deal with the issues listed above, plus a high pH spike at some point during the composting process.

The soil I prefer for all my houseplants and other plant material that will possibly be in the same soil for more than a single growth cycle, is equal parts by volume of:

1/8-1/4" pine or fir bark
Screened Turface MVP
crushed granite in grower size or #2 cherrystone

This soil will retain it's aeration and drainage characteristics for long after it would have been prudent to repot the planting (indefinitely). Because it has a 2/3 stable inorganic component of particles in the 1/8" size range, it is very difficult to over-water and the soil holds no perched water when properly made. It also allows you to water copiously at every watering so salt build-up (a major problem and the cause of death in many plantings with water-retentive soil) can be eliminated as a concern.

Al

I use 1/2 course builders sand 1/4 reg potting soil and 1/4 peat moss, all but my cacti like it, for them I use 3/4 sand 1/4 peat moss. Works for me and my plants.

I've always just used a multi-purpose compost, but, after having my eyes opened on this site, I've bought some Perlite and ordered some Pine bark on eBay and will start mixing my own soil from now on. If that is successful, I may start getting a bit more adventurous with my soil mixes.

On a related note, when the time comes to move my plants into bigger pots, is it recommended to wash most or all of the old soil off first and just plant the bare root ball into my new, improved soil. If so, is it fairly easy to do without damaging the plants?

Paulie,

I did that with all my houseplants a couple months ago, due to a gnat infestation, which I rapidly learned much from.. One at a time, I took them all down to bare root, being careful to clean all the old soil and planting them in a much more desired, and sterilized potting medium. They all transitioned well and are thriving.

This message was edited Nov 15, 2009 5:57 AM

That's good to know, daisy. I'll start in Spring with some of my smaller plants and see how easy/difficult it is. Having never done it before, this may sound naive, but how do you make sure to pack the new soil in-between the roots?

LOL, I'm still pretty naive about much to do with this too. Honestly, I just put about 2/3 of the amount of potting medium needed, placed a plant in it.. Then I added the rest of the medium, gently tapping the pot as to avoid air pockets. Not sure if that is "right" but that is all I did and my plants are doing just fine.

Sounds like you're right on track, Tracy. ;o)

Something good to remember is that 'rich and black' in container culture most often does not equate to the same thing it does in the garden as it applies to soils. Well-composted, rich, black soil materials are often comprised of very small particles and by default are then very water-retentive. This is not usually a good thing in container growing. The ideal state of water retention in most cases finds your soil at about the same water retention as a wrung out sponge. In this state, aeration is maximized and the plant still has plenty of water.

Most out of the bag soils are very water retentive, which means they don't hold enough air in the soil, even when new, to give your plants the opportunity to realize their genetic potential. Soils that support a soggy layer of water at the bottom of the container are a problem. If you water properly so that you flush the soil each time you water, you have to deal with that saturated layer of soil at the bottom of the container. Roots, when deprived of 02, begin to die within hours. This means that even if your plant exhibits no visible signs of of trouble, roots are still going through a cyclic death and regeneration (hopefully - when enough air returns to the soil to allow normal growth), which is a drain on energy. The energy the plant uses to grow the new roots killed by a soggy soil would have gone into creating more mass; that is to say more foliage or blooms.

Soils are the very foundation of every planting. If makes little sense to but a $10 plant in a 25 cent soil. ;o) If you start with a poor soil, it's not going to get better. As soils collapse structurally (as particles break down) they hold less & less air. When using these water retentive soils, you need to make a decision every time you water. "Do I water properly, so I'm flushing the accumulating salts from the soil and risk root rot, or do I water by giving the plant just a little sip, so there is no worry about root rot, and ignore the accumulating salts in the soil that, uncorrected, will surely kill the plant eventually (or at least severely restrict it's potential to grow well)."

If growers ask themselves one simple question before they pot a plant, they can make their husbandry duties a whole lot easier. "Will this soil provide the structural stability to guarantee ample aeration until the next repot?" Every other cultural condition can be changed after you establish the planting - light levels, temperature ....... The soil is more difficult,m and specifically how well aerated the soil is, is much more difficult to change.

I have none of the troubles with diseases, insects, burned leaf tips/margins ..... that these forum pages are filled with, and I attribute that to my choice of soils. Plants growing with high vitality are producing the bio-compounds (that are a product of metabolism) that increase the plant's resistance to these problems. Well-aerated soils also practically eliminate the problems of over-watering and salt accumulation.

Al

A little feller in 100% Turface fines:

Al, what plant do you think will be most remarkable in a trial on of your gritty mix? Thank you :).

If you follow the very simple fertilizer program, one of the more obvious improvements over peat/coir/compost-based soils you should see is a very noticeable increase in vitality. This will be due to A) increased aeration B) a near constant supply of nutrients in the soil at low concentrations (which makes it easier for the plant to take up both water and the nutrients dissolved in water C) the fact that if made properly, it is very difficult to over-water plants in the gritty mix D) no build-up of soluble salts because you are able to water copiously, flushing the soil at every watering. The increased vitality also decreases any probability that you will see insect or disease infestations because the plant produces various anti-feedants, anti-metabolites, and toxins that make the insects feel pretty unwelcome as a by-product of metabolism and increased vitality/metabolism means a more resistant plant. A healthy soil also produces a better looking plant w/o the burned tips and margins associated with the over-watering and salt build-up inherent in heavy soils.

Al

Well, do any type of plants prefer this over the 511 mix? What about a ficus carica? Is that a good candidate? And would you use equal parts turface, grit, bark for ficus? I have no feel for working with this potting mix yet so want your opinion to get the best results.

I finally have the bark!

Yes - I have at least 30 ficus, covering about 8-10 species in the gritty mix, including hardy figs (carica). I also grow all my tropical, subtropical, and temperate trees in the gritty mix. The primary difference between the gritty mix and the 5:1:1 mix lies in the fact that, properly made, the gritty mix offers superior aeration and greater longevity (it's 2/3 mineral as opposed to the approximately 15% mineral content - perlite - of the 5:1:1 mix. This isn't as large an advantage for plants that you are growing for the short term, but it can be a considerable advantage for long term plantings, within the limits of what is prudent as far as repotting intervals is concerned. The gritty mix also allows for much easier and faster repotting. (I draw a distinct difference between repotting [which includes soil removal and root-pruning] and simply potting-up.)

Al