I'm not asking because I want to know; rather, because there is a great deal of misconception re just what a soil should do for plants growing in it. I'm hoping the conversation provides understanding which allows growers to get beyond having to fight the medium for control of their plant's vitality.

Al

LOL There are not a whole lot of people on here who actually want a real discussion about anything.
I found my mix for epiphytic and terrestrial epiphytes by accident. I used to be addicted to growing Heliconia, Etlingera elatior and other large growing Zingiberales from single start (rootless) rhizomes. At one time I had over 40 different heliconias alone. The trick to getting the starts to root and not rot is largely in the potting media you choose. I did a lot of research and asking my various older 'plant mentors' and basically came away with the message of 'porous, fast draining, but still nutrient retentive'. So I fiddled around with stuff and came up with a starting mix that worked very well for my rhizomes. I had a very high success rate with rooting, and being able to transplant into the ground later. That recipe was basically 1/3 perlite or substitute (chopped styrofoam peanuts, chopped corks from wine bottles), 1/3 peat, and 1/3 fir bark (or substitute...hard nutshells work very well, so do compressed clay pellets).

When I started growing a lot of aroids 20 years ago, I basically used variants of this same mix for the terrestrials, and a slightly different mix for the epiphytes. (peat vs no peat) and for lithophytes I use other pumice or ALiflor (LECA).

For me its knowing how a plant grows in nature and WHERE (up a tree, down a sheer rock face, in a crevasse, etc) that informs what I pot it in. Or what I fill into a hole I dig in the sand here to plant it in.

Developing the root system is first and foremost, the lovely beautiful top growth follows.

Thanks for the reply, Gina. I went through the same process. Almost 40 years ago I was smitten by the bonsai bug. The instant I saw (by accident) the trees being set up for a show, I knew I was going to learn how to do that. I tried my hand for the summer and failed completely. This was back before there was something called the internet, so I set aside the trees and hit the books. 3-4 years years later, I decided I might have enough knowledge of soil science and plant physiology to keep my trees healthy. It's no fun to practice bonsai on a new tree every week and have the age of your oldest tree measured in months, sometimes weeks! In retrospect, the reason for failure stands out conspicuously as poor choice when it came to growing media. Fix that - fix a plethora of problems.

Your medium works because it's made of almost all coarse materials. Water sticks to itself (cohesion) and to the pot and soil particles (adhesion). The sum of water's adhesive and cohesive properties can be stronger than gravity. That's why, when you hold a sponge by a corner, ALL the water doesn't drain out of it. Once it stops draining, you can wring a lot of water from it. If we were growing a plant with a sponge as the medium, and we watered as we would our container media, all the excess water in the sponge - the water that can be wrung out of it after gravity has done all it can to drain the sponge has its equivalent in container soils and it is extremely limiting to root health.

What drives water retention in container media is primarily the size of particles in the medium; so, the larger the % of fine materials in the medium, the more water retentive the medium will be. If all particles are 1/10" or larger, the medium could hold NO excess water between soil particles. There would be no such thing as over-potting, we would have to work very hard and intentionally to over-water, and there would be no (as in zero) limitations from too much water in the potting medium. What kills more houseplants than any other cultural adversity? Over-potting/ over-watering - too much water in the potting medium.

Getting to the point where WE, instead of the potting medium, control of our plants' vitality literally changes the plane on which we interact with our plants. It makes that much difference.

Al

That is an argument I have voiced here on many threads where someone is having a lot of problems with soil remaining waterlogged, or plants suffering root loss. I always suggest repotting the plant into a more porous less water retentive media, but always get shot down by the anti-repotting faction.

The advent of what I term the 'New Aroid Craze' (as opposed to the old one, which ended c2009/10 with the last big recession and the extreme slowdown in tissue culturing of many more unusual plants in US in favor of the usual quick selling landscaping plants has led many many people to buy what used to be rare expensive plants, which became 'not-so-rare' and 'not so expensive' during the days of mass tissue culturing of many species, and are now again 'more rare' because there was no interest in them for so long that only the markets in Asia and the Netherlands are really doing mass TC again. The US has not caught back up to that.

So people are spending oodles on money on small starts of plants, sometimes importing them from Asia, and not knowing how to grow them. Social media has allowed the advent of groups of people now getting together with the likes of research botanists and other genuinely knowledgeable people and exchanging information and ideas on the best way for people to grow these plants as houseplants and greenhouse specimens. (I don't grow any houseplants, mine are all greenhouse grown, but I can still certainly take advantage of the goldmine of information being shared).

One of the main things that has come out of this new aroid/housepalnt craze is the new thinking of addressing the potting medium INSTEAD of the watering 'schedule'. The terrarium/vivarium industry has also been instrumental in helping to assist this line of thought.

I personally believe that the worst medium to pot ANYTHING in is bagged soil-less potting mix. Especially if it already has fertilizer mixed in. If I want something that resembles that, I will use peat.

Many of the epiphytic aroids need to be treated like orchids. They want the water to run over their roots, let them absorb as much as they want, and the rest drain away quickly. That has NEVER happened for me with ANY commercially bagged potting soil I have tried. That is why I make my own mixes, and I think my plants thrive because of that. AND because I am not afraid to repot a plant if I think it needs repotting.

Gina and Al, and Will C also--thanks for this cogent discussion! I've noticed the "(almost) never re-pot" advice, in contrast to the "get it in the right mix NOW" advice and also the "pull it out of the pot and check the roots" advice. I've done a little of each with different plants at different times, with both success and failure. I find it really helpful to understand the reasoning. The information about soil particle size, drainage and perched water has been particularly helpful.
Now that many people are reading and typing on a phone, discussions tend to be short. Just wanted to let you know that you have a least one reader here!

Not repotting when a plant needs it is just silly. Some plants can stay in a pot almost forever...Hoya do not like to be repotted all that much, and since they are quite epiphytic, they do better if they are potted once in really good media (which the stuff they generally come in from the nursery is way too water logged and heavy to leave them in) and then left. I have one that has been in the same 4" terra cotta pot for 18 years. And its huge and climbs all over theGH wall.
But the plants need to be repotted once in a while. The soil loses nutrients, the soil can have salt and mineral build up from fertilizing, orchid medium gets old, the plant 'uses up' the soil and becomes root bound...or the media is just not suited to the plant. This is there case with a lot of epiphytes that you get from the nursery. The only epiphytes I get that seem to be appropriately potted are ones from other collectors. Because we have learned over time to address the media for the best success.

MsDoe - Some take a laissez faire approach to gardening, and that's fine - there should be no judgment re how others order their priorities. Others' priorities allow some time to learn and implement practices that allow their plantings much greater opportunity to realize a greater share of their genetic potential. All plants (other than mutants) are capable of becoming beautiful specimens. Since the grower is a potted plants only provider, the only thing prohibiting the plant from realizing ALL of its potential is the gardener. That's our job - figure out what's limiting our plants and eliminate the limitation. What else is there? Those who want to increase their proficiency at container gardening/ rearing houseplants probably have a stronger nurturing bone, and get a greater sense of self-satisfaction for their efforts on behalf of their green friends. If this thread gains some popularity, I promise the participants will learn how to significantly improve the effort:results ratio. I know this because I've been overseeing a similar thread on another site that's been active for 15 years and has over 7,000 contributions to it and still going strong. In order to get a sense of how much attention thread has generated, do a quick google search using the search words 5-1-1 mix and note the number of hits.

The medium you use in a planting will almost always have more impact on how much of their potential your plantings can/will realize. Sunlight is very important, but you either can or cannot move plants to the most appropriate light conditions. Once a planting is established, you're stuck with the medium until it's repotted. I'd guess that about 90% of the issues for which people come here seeking remedial advice are related directly to poor root health caused by a combination of a poor medium and a heavy hand on the watering can. I've helped thousands of growers rid themselves of the limitations caused by the dastardly duo of poor soil/ over-watering which limits roots' ability to function normally and/or wrecks root health.

As far as repotting goes (not potting up - that's different), it has a remarkable rejuvenating effect. I've seen advice repeatedly that repotting is bad and it kills the fine root hairs the plant needs to ...... horsefeathers! What REALLY kills fine roots is water-logged media and the advice to 'water when the top inch or two of the medium is dry. In a 10" deep pot, where the top 2" of medium is dry, the lower 6" can be fully, 100%, totally saturated. That means that 60% of the soil is wasteland. It cannot support root growth and it severely limits root function ...... and this is supposed to be the point at which you should water? What's important is the moisture level at the BOTTOM of the pot.

The time to water is when a full handful of soil from near the bottom of of the pot, when squeezed very tightly in your hand, yields a few drops of water, and crumbles as soon as you open your hand. Water uptake is most efficient when the soil is moist or damp, and least efficient where it is dry or saturated; this because dry soil has no water and soggy soil has no air (O2) to fuel the roots' ability to take up water/nutrients and move them around the plant. Example: It's known that Ca(lcium), a major component of cell walls) must be in the nutrient stream at all times if cells/tissue are to form normally. Saturated media limits Ca uptake, so a high % of the symptom of deformed leaves in container plantings is due to a culturally induced Ca deficiency.

When you hold a handful of container media in your hand and see it is made of a very high % of fine particles, odds are extremely high it will be very limiting if you water correctly (flush the soil when you water). If you don't water correctly (instead, you water in sips to skirt potential over-watering) you ensure the dissolved solids (salts) in tapwater and fertilizer solutions remain in the medium, which brings it's own set of issues related to decreasing ability to take up water as the salt level of the soil increases.

Growing well is a holistic adventure, and not all things are as they seem. One thing is certain though, there are no healthy plants with unhealthy root systems.

As far as repotting goes, there is a difference between repotting and potting up. Root congestion (rootbound) becomes limiting/ stressful about the time the root/ soil mass can be lifted from the pot intact. From that point forward, the limitations increase in direct relation to the degree of congestion. Potting up absolutely ensures a large fraction of the limitations imposed by root congestion remain when the up-potting is done. Repotting, which includes bare rooting (or nearly so), pruning roots, and a change of growing medium, ensures ALL limitations associated with root congestion are removed until such time root growth progresses to the stage the root/ soil mass can again be lifted from the pot intact. The only way to skip repotting and not be forced to live with the limitations of root congestion is to pot up before the congestion gets to the stage where root/soil mass remains intact when lifted from the pot.

The most vigorous tissues on a plant are found at the root to shoot transition zone. Any time you cut a plant back nearer to the transition zone, it has a strong rejuvenating effect on the plant - very strong. Typically, I repot a plant and within 1-2 weeks it's pushing new growth. This tells us absolutely the root system has recovered to the degree it can actually support more top growth. Not only that, if all else is equal, in spite of losing the growth that would have occurred during the recovery period, by the end of the growth cycle the repotted plant will be much larger and healthier than the plant potted up.



Al

I am really glad you brought up Calcium. Many of the plants I grow need supplementation of not only Calcium but also Manganese and Boron. These are not the 'usual' components of stuff like Miracle Gro water soluble. They have to be supplemented with either a more complete all-in-one that contains trace elements and micronutrients, or those things have to be fed separately in addition. But as the name says, TRACE and MICRO mean you don;t need a whole lot to get results.

One of the things that people who grow a lot of tropical plants and aroids have begun using is Dolomite. It is a limestone product and provides a lot of things that my favorite genus, aroids, need. Many aroids in nature are found growing epiphytical in shallow poor soil and leaf litter over karst formations, which are limestone formations. Limestone is very water soluble, living in Florida, we know all about it because it is what comprises the Great Florida Aquifer which filters and produces our drinking water. Water seeping through limestone layers is also what can cause sinkholes. When the water from rain flows over karst formations, the plants pick up the Calcium and the nutrients as they flow by and utilize them.

I ditched the 'water when the first 2 inches of media seem dry' many years ago. Adding Dolomite to the porous media before potting or when repotting, or using as a top dressing on an already potted plant, is a great addition to the feeding routine. In the media I use, I can water every single day and not drown the roots of my plants. (of course I don;t water every day in summer, because our humidity is 80-100% day after day and that helps the media stay moist longer. But in the much drier months of winter, the plants get water a lot more frequently.

When I refer to a 'potted plant' in my own collection, more other than not I am referring to a hanging wire basket with a coir liner filled with a very chunky porous mix and the roots of the plant may be poking through and growing over the edge. Because that is what epiphytes do, and the majority of my collection that is in a container is an epiphyte. I do have other containerized plants that are terrestrial and also many plants planted directly unto the ground. Each plant has its own needs and I strive to meet the needs of all. I love hearing other people's take on this issue, and think that tapla makes very salient points about many issues faced by container/houseplant growers that are really valuable.

Thanks, Gina. I appreciate the kind words.

"Many of the plants I grow need supplementation of not only Calcium but also Manganese and Boron. These are not the 'usual' components of stuff like Miracle Gro water soluble. They have to be supplemented with either a more complete all-in-one that contains trace elements and micronutrients, or those things have to be fed separately in addition. But as the name says, TRACE and MICRO mean you don;t need a whole lot to get results." All plants need all the essential nutrients plants normally get via the root pathway in order to grow normally, and a large fraction of plants we grow as houseplants don't stray too far from using about 6x as much N as P, and about 3/5 as much K as N. Here's a chart I put together for the average plant:
I gave Nitrogen, because it is the largest nutrient component, the value of 100. Other nutrients are listed as a weight percentage or fraction of Nitrogen:
N 100
P 13-19 (16) 1/6
K 45-80 (62) 3/5
S 6-9 (8) 1/12
Mg 5-15 (10) 1/10
Ca 5-15 (10) 1/10
Fe 0.7
Mn 0.4
B(oron) 0.2
Zn 0.06
Cu 0.03
Cl 0.03
M(olybden) 0.003

To read the chart: P - plants use 13-19 parts of P or an average of about 16 parts for every 100 parts of N, or 6 times more N than P. Plants use about 45-80 parts of K or an average of about 62 parts for every 100 parts of N, or about 3/5 as much K as N, and so on.

Dyna-Gro's Foliage-Pro 9-3-6 provides all essential nutrients in the ratio at which plants actually use them, which is a significant plus because it allows you to fertilize at the lowest fertility level possible w/o plants suffering a deficiency. It also contains Ca and Mg, both more often than not lacking in soluble fertilizers.



Another significant advantage is it gets 2/3 of its N from nitrate sources and NONE from urea. Urea is known to promote coarse growth generally and very coarse growth under low light conditions (think houseplants). Coarse growth means large leaves and long internodes, so it's harder to keep plants full and compact using fertilizers with urea as a N source.

I use Foliage-Pro 9-3-6 on everything I grow, though I do Dr it slightly for a very few plants - mainly hibiscus and tomato.

"One of the things that people who grow a lot of tropical plants and aroids have begun using is Dolomite." Dolomite, or dolomitic limestone has been the staple liming agent for container media since our grandma's grew things in garden soil/ topsoil. Its solubility is determined largely by soil solution pH and it's particle size. It raises pH of media to a more favorable level and provides a supply of Ca and Mg. The Mg fraction of dolomitic lime is about 125X more soluble than the Ca, so containers that have been established for several years should probably get a small Mg boost from Epsom salts from tome to time as the Mg fraction is depleted. Continuing to supply lime as a source of Mg will boost the Ca supply and make Mg difficult for the plant to absorb (an antagonistic deficiency).




Al

I don't seem to have too much trouble with potted veggies (although they don't produce like the ones in the ground), but I do have more problems with roses and small tree/shrub starts.

I did come to the conclusion that regular potting soil for roses and small trees/shrubs wasn't working. Unfortunately, I am now between a rock and a hard place. I realize I need better draining soil and could probably try to remove some soil heavily amend with perlite or bark and see if that will hold my plants over until spring. I am afraid that repotting and removing all soil as we head into winter might not be the best idea. What's your best advice for this?

Annie I don;t think that AL is here anymore.