Potting mix breakdown

[David_Sweden]

Can anyone describe what a potting mix looks like once it starts to break down? Pics would be nice but also a description: Does most of it end up as small particles (like dust) that is washed out, or is it mostly fiber-like slimy stuff? does it usually happen very quickly or over several years?

I read that soilless media of peat moss, bark or coir typically breaks down after 2-4 years, bark usually lasting the longest but when i starts to break down it can go fast, and coir 2nd longest.

For peat there is the von Post scale, which describes the most broken down stages as H10 "No discernible plant structure; when squeezed, it all escapes between the fingers", H9 "Hardly any recognizable plant structure; when squeezed it is a fairly uniform paste", H8 "Very indistinct plant structure; when squeezed, about two-thirds escapes between the fingers; a small quantity of pasty water may be released. The plant material remaining in the hand consists of residues such as roots and fibres that resist decomposition", H7 "Very faintly recognizable plant structure; when squeezed, about one-half escapes between the fingers. The water, if any is released, is very dark and almost pasty" etc. But when does which of this occur - if they actually occur in this order in a pot, and how quick from H5 to H6 to H7 etc? The descriptions to me indicate that much is washed out (as dark pasty water) and the rest is slime but does it stay put or is it washed out?

Reason for trying to understand this is that many recommend not removing old soil when repotting, which means no matter which organic material you chose, it will break down, and what remains is the mineral part, and maybe organic slime? It is a topic specific for palms in pots (more or less) since for most other plant types is usually recommended to remove soil and repot before rootbound. Not many recommend that for palms (except for some species known to survive such repotting and even root pruning for a few types).

And for a special prize: If soil initially is 50% organic and 50% mineral, after 10 years, is it then 100% mineral or what?

[Gonzer]

David, instead of analyzing the soil components and their structure to such an extent a good rule is to freshen up your palms in pots with new soil, regardless, ever few years. This aids the overall health of your plants and ensures a better structure for fertilizer uptake. Besides, who wants to wear the same  pair of underwear for years on end?

 

 

 

 

 

 

[TexasColdHardyPalms]

From my experience it will go granular and "crumbly" and then starts to disappear very quickly after that. I know it sounds strange but the plants will eat/absorb all of the organics and you'll be left with a few sand particles/shale/etc wedged in between the roots. Two years is what it takes with a compost/bark/sand mix. The less you fertilize, the faster the soil decomposes. 

We do NOT remove the old soil when potting up as the "old" soil will be completely displaced by larger roots soon after repotting. 

[David_Sweden]

Thanks Joseph, interesting. So after a few years just mineral parts remain?

The 1st link above says about aging soil "The root network will tend to keep the soil aerated by creating a woody framework." and "fine particles will often be washed out of a healthy root network", I guess he's basically saying the roots themselves create the structure that gives the soil air filled pores then. Makes sense to me and I think one of my palms have that situation (but not the ones with slower growing roots). He is the only one I ever saw stating this opinion though, but sounds like you agree if I understand your last sentence correctly?

Then again I heard others complaining about how peat moss based soil gets gooey when wet and like a hard cake when dry but that sounds to me like peat moss with too much fine particles (too decomposed or too finely shredded) and maybe not a problem of aging soil but just bad quality from the start.

[David_Sweden]

I found a couple of threads here with some more info on what broken down soil might look like:

1) A severely root bound Archontophoenix purpurea that was doing well, looks like not much soil left at least on the outside, maybe that's a clue to my question. Can't see center but he peeked into the outer parts and found mostly roots and a little soil if I understand it correctly.

2) Jeff Searle writes about checking a root ball: "if there's a a few inches of soil from the bottom up, that looks very compact and even has a shiny look to the soil, this area of soil has begun to break down and your getting root rot damage". This obviously is a situation when the palm is not pot bound. But interesting description of broken down soil (unknown mix).

Edited November 1, 2017 by David_Sweden

[DoomsDave]

David:

The humus in potting soil breaks down, and literally evaporates after a while, leaving sand, perlite, vermiculite, lava rock, etc. I've had palms potted in what amounted to pure sand after a long time.

As noted above, repot with new soil, take care to pack it in gently, then keep moist.

Palms can get hugely rootbound and still be okay. Most kinds, anyway.

Good luck!

On 10/29/2017, 3:38:43, Gonzer said:

David, instead of analyzing the soil components and their structure to such an extent a good rule is to freshen up your palms in pots with new soil, regardless, ever few years. This aids the overall health of your plants and ensures a better structure for fertilizer uptake. Besides, who wants to wear the same  pair of underwear for years on end?

 

 

 

 

 

 

Must concur, underwear, unlike wine, does not improve with age.

[David_Sweden]

Sorry but I don't agree. It seems to me that 9 out of 10 palm growers say palms don't mind being root bound and even prefer it, and recommend to never cut roots (with few exceptions) and repot when rootbound (but maybe not wait until it is completely cramped) by just adding soil around the root ball. Like this page by legendary Palmbob which says "Repotting palms is recommended only if they really need it. Those with a lot of horticultural experience know most plants and trees do not like to be root bound, and cramped roots can make the plant less happy and healthy. Palms are quite different in this regard and seem to almost rather be root bound than otherwise. Palm roots do not seem to suffer from overcrowding until there is far less soil than there are roots in a pot." and "When repotting a palm, it is best NOT to mess with the roots. Some growers recommend unwinding or tearing off excessive roots from other types of plants, but palms have very sensitive roots in this regard and will often sulk, if not die, from this practice. If a palm’s roots are the shape of the old pot, that is a good thing. Just leave them that way and put the whole pot-shaped rootball into the new pot and fill with soil around the roots.". And here are a few threads I found where something like that is said: 1 2 3 4 5 6 7 8 9 10 11 12

So can we please stay on topic? And BTW I don't necessarily agree either that it is ok to wear the same underwear even for 1 year.. :-/

[DoomsDave]

7 hours ago, David_Sweden said:

Sorry but I don't agree. It seems to me that 9 out of 10 palm growers say palms don't mind being root bound and even prefer it, and recommend to never cut roots (with few exceptions) and repot when rootbound (but maybe not wait until it is completely cramped) by just adding soil around the root ball. Like this page by legendary Palmbob which says "Repotting palms is recommended only if they really need it. Those with a lot of horticultural experience know most plants and trees do not like to be root bound, and cramped roots can make the plant less happy and healthy. Palms are quite different in this regard and seem to almost rather be root bound than otherwise. Palm roots do not seem to suffer from overcrowding until there is far less soil than there are roots in a pot." and "When repotting a palm, it is best NOT to mess with the roots. Some growers recommend unwinding or tearing off excessive roots from other types of plants, but palms have very sensitive roots in this regard and will often sulk, if not die, from this practice. If a palm’s roots are the shape of the old pot, that is a good thing. Just leave them that way and put the whole pot-shaped rootball into the new pot and fill with soil around the roots.". And here are a few threads I found where something like that is said: 1 2 3 4 5 6 7 8 9 10 11 12

So can we please stay on topic? And BTW I don't necessarily agree either that it is ok to wear the same underwear even for 1 year.. :-/

Potbound is one thing;  no, or almost no, soil is another. And what happens to standard potting soil is that the humus disappears, and leaves the sand, etc. behind. When that happens, you generally need to replace the soil. Much of the time, you can give the plant a bigger pot too. But what happens when the next pot size is so huge your home or other space won't accommodate it?

In 40+ years of horticultural experience, I've found generalities dangerous (even as I sometimes spout them). In general treating the roots with great care is a good idea, but sometimes you're in a situation where a palm is, and always will be, in a pot far too small for the normal mature plant it wants to be. Phoenix are a great example. If I were to keep a Phoenix in a pot forever, I'd cut back the rootball periodically, to help keep it in bounds in the pot. Many other palms are another matter completely.

I've had palms, outdoors, that had a mass of roots, and almost no soil left. Some, like Phoenix take this a lot better than others, like Dypsis.

This is a great thread, and hope to hear more.

[Monòver]

I renember a Pal Meir post doing this with i think Phoenix rupicola. He was cutting the rootball and the recovery was amazing.

[Sanips]

44 minutes ago, Monòver said:

I renember a Pal Meir post doing this with i think Phoenix rupicola. He was cutting the rootball and the recovery was amazing.

2

It was a CIDP.

On 28/1/2016 19:50:29, Pal Meir said:

Q&A #1: Suckers of Arenga

 

Q&A #2: Root pruning of Phoenix canariensis

 

[Monòver]

26 minutes ago, Sanips said:

It was a CIDP.

 

You are younger than me and your memory is better.

Thanks, this was the pictures.

[David_Sweden]

Monòver, I saw you in this thread, where some of the palms are quite root bound. Can't you contribute to what this thread is actually about and tell me a bit about what the broken down soil looks like, and related stuff like I asked for in the initial post? Did you remove all old soil from within the root ball? If not, then it's still in there today, and that's why I'm interested in what condition it is in after a number of years.

DoomsDave, "the humus disappears, and leaves the sand, etc" is kinda missing the vital part - what about the "etc"?!  I realize coarse mineral stays put and fine particles get washed out. But what about the rest of the organic mtrl? And what does it look like (describe it) and how fast does it go, how does it look at each stage, etc? My view is that it take 2-4 years for most good soils, 1 year if you are unlucky, 5 years if you're lucky.

My spontaneous thought was that the soil breaks down into very small particles (humus-like) which is washed out. But when I mentioned that thought to a professor in soil science he said "why do you think it turns into just small particles" which to me sounded like you also get other residue, maybe slimy, maybe long flat fibers, you tell me. He was obviously talking about peat moss based soil since that's all they sell in my country.

The only palm that's grown big enough yet in my apartment to hit the ceiling so that I had to give it away to a botanical garden was my old Kentia. First repotting ever (by me) was in July 2015, you can see the old pot in the small pic and the growth is over 3 years:

I remember the old soil as being quite dense but not completely inpenetrable and full of small roots from top to bottom. Until 2014 it never gained height, it put on new fronds but old ones died as quickly. Then I started to learn how to treat it, leaching being the most important change, which I did for the first time summer of 2014, and also learned to water properly (when just moist, water fully, remove water from saucer) and proper fert and light level (and killed off spider mites and top-dressed soil etc). During the year from June 2014 until the first repotting July 2015 the improvement in growth was tremendeous. In June 2014 soil went dry after about a week, in July after about 3 days, that's why I repotted. I know Kentia is one of the easiest palms but anyway, this is the main experience I have of "old soil".

[DoomsDave]

43 minutes ago, David_Sweden said:

Monòver, I saw you in this thread, where some of the palms are quite root bound. Can't you contribute to what this thread is actually about and tell me a bit about what the broken down soil looks like, and related stuff like I asked for in the initial post? Did you remove all old soil from within the root ball? If not, then it's still in there today, and that's why I'm interested in what condition it is in after a number of years.

DoomsDave, "the humus disappears, and leaves the sand, etc" is kinda missing the vital part - what about the "etc"?!  I realize coarse mineral stays put and fine particles get washed out. But what about the rest of the organic mtrl? And what does it look like (describe it) and how fast does it go, how does it look at each stage, etc? My view is that it take 2-4 years for most good soils, 1 year if you are unlucky, 5 years if you're lucky.

My spontaneous thought was that the soil breaks down into very small particles (humus-like) which is washed out. But when I mentioned that thought to a professor in soil science he said "why do you think it turns into just small particles" which to me sounded like you also get other residue, maybe slimy, maybe long flat fibers, you tell me. He was obviously talking about peat moss based soil since that's all they sell in my country.

The only palm that's grown big enough yet in my apartment to hit the ceiling so that I had to give it away to a botanical garden was my old Kentia. First repotting ever (by me) was in July 2015, you can see the old pot in the small pic and the growth is over 3 years:

I remember the old soil as being quite dense but not completely inpenetrable and full of small roots from top to bottom. Until 2014 it never gained height, it put on new fronds but old ones died as quickly. Then I started to learn how to treat it, leaching being the most important change, which I did for the first time summer of 2014, and also learned to water properly (when just moist, water fully, remove water from saucer) and proper fert and light level (and killed off spider mites and top-dressed soil etc). During the year from June 2014 until the first repotting July 2015 the improvement in growth was tremendeous. In June 2014 soil went dry after about a week, in July after about 3 days, that's why I repotted. I know Kentia is one of the easiest palms but anyway, this is the main experience I have of "old soil".

The humus is the organic matter, or the bulk of it. The "etc" encompassed other inorganic materials like perlite, vermiculite, lava rock, gravel, anything else. Deteriorating humus just sort of fades away; sometimes it washes away, too. How long that takes can vary a lot. If you water a plant a lot, and, if a lot of that water rushes out the bottom, soil can get washed away or deterioriate in about three years. Some soils hang around a lot longer. If the soil doesn't deteriorate, it kind of clumps together.

I'll see if I can find some examples from my giant Container Ranch.

Also, if soil isn't packed into the pot it can wash out before it deteriorates. I've had that happen, especially after I dug and moved something from the earth to a pot, and didn't carefully pack the new soil in the pot to avoid "channels" that become little rushing rivers.

VERY NICE Kentia! I couldn't grow it that well indoors myself. They appreciate plenty of water. Other species, not so much.

[David_Sweden]

Thanks Dave, then I understand what you mean! The way I learned it, humus is what you get after complete humification, i e the dark part of the soil with only very fine particles. But the term is used differently by different persons. 

BTW I'm also curious about what happens to vermiculite after a number of years when part of pot bound soil. I find the material fascinating (popcorn made of rock!) but I am leaning against never using it again for palm trees because it will get permanently compressed and/or break down into small flat pieces and dust. Fine for smaller plants though.

[David_Sweden]

Found a pic of what coir might look like after 3 years (although I read it usually lasts over 4 years):

[David_Sweden]

The reason why I am trying to gather info on what potting media looks like when aged is that I am trying to decide on what soil mix to use from now on. I believe one should start out with a good organic component (or mix of them) and then add 0-50% mineral, and after the tests I did here only 100% coir is of interest for me to try. If I felt sure that I would swap the soil within 3 years then I would probably choose 100% coir, I can't see any reason to add minerals then. But I want to leave it in the pot until it gives me a reason to repot like very frequent watering, decline like slower growth or other issues, or evidence soil poposity is declining (maybe 1-4 years). When I at that time take the root ball out I think I can be met with one of the following scenes:

1. Very much rootbound, not much organic mtrl left and impossible to swap soil. Roots have filled the pot and created a texture that gives porosity that gives aeration and drainage. In this case I would choose to just add soil around the root ball.
2. Not rootbound at all, easy to replace (almost) all soil. In this case I would probably replace 60-90% of the soil. I kinda doubt this situation would pop up though unless I repot every year. More probably I could replace 60-70% of the soil because the rest feels to hard to rip out without hurting it and even then I would worry, and mist it every 2 minutes. And then it would look more like scenario 3.
3. Something in between.

It would good to have a soil that works for all 3 scenarios.

I'm considering adding 30-40% seramis, which I think has no benificial effects compared to 100% coir if I swap all soil at repottings, but in case I (must) choose to leave some soil in there, I'm thinking the seramis might make the situation slightly better by binding a little water and having rather high CEC (although I have concluded CEC is not necessary if one adds fert at every watering or use slow release fert, and in any case CEC binds mostly Ca2+ and Mg2+ while most N, P and K is water soluble - I intend to add my findings on CEC in this thread when I find time).

It would be interesting to understand what "scenario 1" looks like in more detail though. If the soil breaks down and is not fully penetrated by roots I imagine it doesn't matter what mineral is in there, it will be very low in porosity and needs to be replaced. But in scenario 1 after several years when soil has broken down and (based on what I heard so far) mostly left the pot, I wonder if perhaps the situation is that soggy soil exists in thin layers in between roots, which does no good for aeration but the roots can just turn the other way for that, so that one would end up with large areas with just roots (and mineral) and some thin pockets of soggy soil here and there? How well can such soil hold water even for a day? And capillarity would be non existent?

I often read about roots circling pot bottom when beginning to get root bound and I've seen this in a couple of palms, but e g my Lipstick palm is funny in that it seems to have fully penetrated all of the soil and needs watering every 2-3 days, but the roots do not stick out the bottom it just barely reaches the holes, seems like the roots run vertically then end without circling. And this is the happiest palm I ever saw (small pic shows it 2 years ago):

It is part of my self-watering pot experiments with a couple of wicks sticking up the bottom part. Soil still has capillarity (wicking ability) that spreads moisture quite well all over the volume, possibly much due to the recemtly added soil outside the old root ball, but all of the old soil is alse rather evenly moist. Soil is not very dense (letting pot boundness go that far sounds like too much).

Could the way soil works for a potbound palm with broken down soil be that the soil (even if old and soggy and in thin layers) is needed to spread water within root ball (since the way roots suck water from soil not adjacent to the roots is by gradients, i e water wanting to move by itself from where there's much to where there's little)? So that when people say "this old palm seems so root bound there is no visible soil just roots but still does good" maybe thin pockets of soil exist which are important for water getting to the roots? And that maybe air gets there from "the other side", the pockets filled with roots? Sound like a believable theory? How else to explain that root bound palms so often do very well? If it is true: Should I add seramis or not? Too much might disrupt the small pockets of soil. But it might help areation as well as aiding a bit with water an nutritient supply. So maybe 30% then?

[SubTropicRay]

David, in my experience the soil become crumbly and unable to hold much moisture.  After some time, it even repels water.  My potted plants also sit directly on the ground and worms often get inside further breaking down the soil.  This benefits the plant for awhile as the worm castings are priceless but after awhile, the soil goes into the state I mentioned above.

[David_Sweden]

Thanks Ray, very interesting. Is that loam based soil or soilless? Worms do a great job outdoors but wouldn't want one in a pot since they create the stuff that is low on aeration.

[Dave-Vero]

"Potting soil" sold in garden centers in the US is really odd stuff, heavy on what I suppose is peat, and tending to turn to goo.  The stuff seems fairly uniform nationally.  Reputable nurseries and botanic gardens use commercial mixes that vary locally.  Florida's seem fairly distinctive, reflecting ingredients that are available in our weird sand, limestone, and muck environment.  

A local bonsai expert uses Turface MVP  for his little trees, which of course get watered daily and have no nutrient problems.  I'm interested in trying this small-pellet baked-clay as a rather expensive potting supplement.  It's intended for baseball diamonds.  

Palm root systems really are entirely different from dicot tree root systems.  There may be some literature on root pruning and such, but my guess is that apart from loosening roots before planting, little needs to be done.  I am, however, bothered by two relatively recently planted palms that haven't yet grown trunks but got blown over by hurricane Irma, which wasn't such a big deal in our area.  Failure of roots to spread??

 

[David_Sweden]

In much of Europe we have the problem of manufacturer mixing in a large portion of decomposed peat (peat humus), a tradition I believe was started by the Dutch many decades ago. In the US I read that the Univ of California mixes from 1957 and Cornell's "Peat-Lite Mixes" from 1963 still dominate, both of which are based on light sphagnum peat moss, and the way I interpret the original texts, they either used very light peat (maybe humification degree H2-H3 or so), or (based on a remark Boodley later made on that H3-H5 is best) maybe slightly darker, but still all peat moss being light (H1-H5). But I read at the main site for Canadian peat moss that they provide rather decomposed peat moss when it comes to amateur growers.

I also read here (written by a M.S horticulturist) that in the US, peat moss based soil mixes in general are expected to be made of light peat moss (not decomposed much). So I wrote him an e-mail and asked about the situation in the US today and he was kind enough to reply, and said that many/most amateur gardener potting soils are made from a combination of sedge peats, composted "forest products,", etc, whatever is least expensive for producers to obtain - and appears "black" (and that it's even happened that  producers add ground charcoal to the mixes to make them appear even darker than they would otherwise), but also that it is not too difficult for amateur gardeners to obtain the same growing mixes used by the most sophisticated commercial greenhouse growers via local distributors and online sources.

If I read in forums, people who know anything in the US seem to recommend to look for light peat moss. And if I look at all the Pro-Mix soil mixes recommended for trees in pots, Pro-Mix TBK contains "select long-fibered blond sphagnum peat moss" and is described as "blond to light brown", and the same description is used for Pro-Mix HPCC, S, B, BRK, BRK20 and BX, and BX is described as "fibrous". In addition there is one type with mainly bark. The only dirt they sell with a mix of "blond and black peat moss" is PRO-MOSS BBK which is for mushroom growing, and is described as "from brown to dark brown in color".

So in the US you seem to be able to avoid this crappy soil, but not in Sweden, even though we are a big producer of peat. I found 2 soils with just light peat moss (one unobtainable to amateurs) but both evidently were too finely shredded since drainage was crappy when I tested it. I believe one major item the soil producers fail to consider is big plants in pots for which the soil needs to be compacted a bit for them not to risk falling. Adding mineral usually doesn't help, even makes things worse. That's why I am trying coir now. Am just going to measure conductivity and pH first and decide on an amount of mineral (probably 30% seramis).

But sorry now I am the one running off topic. Do you have any more info on what soil looks like in a pot after having (started to) break down?