Christmas Cactus are "jungle cacti" that grow in trees and prefer more frequent waterings than desert cacti, which you mention. As you can imagine, in nature they receive bursts of rain and then very good drainage due to their growing location. CC will do very well in faster soil.

Josh

Hi, Joel.
I'm guessing you've read the thread "A Soil Discussion"? If not, may I invite you to read it?

I'm glad to see you're graduating toward coarser, more freely draining soils. If I can make a suggestion: As you progress, with aeration in mind, think also of durability and longevity/serviceability of the soil. Including a larger amount of inorganic components in the soil will increase its useful life. If you select ingredients that offer both good drainage AND water-holding ability, your sacrifice in the need to water more frequently will be minimized. We can talk more about this if you prefer.

Some plants do not take to root-pruning well (palms, eg), but the vast majority of them REALLY appreciate the rejuvenational properties of major root work. I'm not at all delicate in my treatment of rootage when it comes time to repot (completely different from potting-up). Usually I chop or saw the bottom 1/2-2/3 of the root mass off, bare-root the plant, stick it back in the same pot with ALL fresh soil, use a chopstick to move soil into all the spaces/pockets between roots, water well & put in the shade for a week to recover.

I find that time after time, plants treated in this fashion sulk for a week or two and then put on a huge growth spurt (when repotted in spring or summer). Growth INVARIABLY surpasses what it would have been if the plant was allowed to languish in it's old, root-bound haunts. Potting up is a temporary way to rejuvenate a plant, but if you look ate a long-term graph of plants continually potted-up, you will see continual decline with little spurts of improved vitality at potting-up time. This stress/strain on plants that are potted-up only, eventually takes its toll & plants succumb. There is no reason most houseplants shouldn't live for years and years, yet we often content ourselves with the 'revolving door replacement' of our plants when just a little attention to detail would allow us to call the same plant our friend - often for the rest of our lives if we prefer.

I agree with Josh's comment about the CC, too.

Al

Hi Joel (and Al)
So what would be the recipe for a medium that would offer good drainage and hold water. (apologies in advance to Al if you are have given that info out already in another post)

Al, thanks. I guess you're saying that the need to pot up is often a delusion... that in most cases root pruning will keep the root mass within a smaller volume while actually boosting the vitality of the plant. Have I got that right?

Okay. What about root disturbance and root pruning resulting in shock that might cause a lushly leafed plant to lose leaves? Frankly, it's only been the rare indoor plant that I've ever select for its blooms. Mostly I choose plants for their foliage, on the one hand, and their suitedness to my latitude/light conditions, on the other. So I generally hate to see a loss of older leaves occur. I find it so rare that indoor plants will replace lower-on-the-shoot leaves... even when I've cut back the tip significantly to eliminate the apical domination effect.

For instance, I currently have a wonderful heartleaf philodendron. It needs neither potting up nor re-potting at the moment, but when one of these actions becomes advisable, I'd really hate to shock it into losing any leaves. But I'd imagine that you might say 'at that point, what have you got to lose - if you don't repot, you'll lose older leaves anyway'.

J.

Al, you wrote: "You'll need to pot-up, at a minimum, if you want your plants to exhibit good vitality, but potting-up is a quick fix and much less effective than fully repotting plants (which includes root-pruning & removal of all or a substantial portion of the old soil) that tolerate it, which is the vast majority. Even though the plant will usually show some short-term improvement in vitality immediately after potting-up, that practice virtually insures the eventual demise of the plant."

Is there any rule of thumb as to how often to root prune? Or to remove and replace the old soil?(yes, I realize some soil mixtures last longer)

And, while I'm asking, would you have any specific recommendation for a heatleaf philodendron?

J.

Is there any rule of thumb as to how often to root prune?

I'm going to answer as if you included 'repotting' in your question.

There is no hard, fast rule here. Some of you grow plants strictly for the blooms, and some plants produce more abundant blooms in containers when they are stressed in some manner. Often, that stress is in the form of keeping them root-bound. I'll talk about maintaining a plant's vitality & let you work out how you want to handle the degree of stress you wish to subject them to, in order to achieve your goals. Before I go on, I'd like to say that I use stress techniques too, to achieve a compact, full plant, and to slow growth of a particularly attractive plant - to KEEP it attractive. ;o) The stress of growing a plant tight can be useful to a degree, but at some point, there will be diminishing returns.

When you need to repot to correct declining vitality:

1) When the soil has collapsed/compacted, or was too water-retentive from the time you last potted-up or repotted. You can identify this condition by soil that remains wet for more than a few days, or by soil that won't take water well. If you water a plant and the soil just sits on top of the soil w/o soaking in, the soil has collapsed/compacted. There is one proviso though: you must be sure that the soil is wet before you assess this condition. Soils often become hydrophobic (water repellent) and difficult to rewet, especially when using liquid organic fertilizers like fish/seaweed emulsions. Make sure this effect is not what you're witnessing by saturating the soil thoroughly & then assessing how fast the water moves downward through the soil. The soils I grow in are extremely fast and water disappears into the mix as soon as it's applied. If it takes more than 30 seconds for a large volume of water to disappear from the surface of the soil, you are almost certainly compromising potential vitality.

I'll talk about the potential vitality for just a sec. Plants will grow best in a damp soil with NO perched water. That is NO saturated layer of water at the bottom of the pot. Roots begin to die a very short time after being subjected to anaerobic conditions. They regenerate again as soon as air returns to the soil. This cyclic death/regeneration of roots steals valuable energy from the plant that might well have been employed to increase o/a biomass, and/or produce flowers and fruit. This is the loss of potential vitality I refer to.

2) When the plant is growing under tight conditions and has stopped extending, it is under strain, which will eventually lead to its death. "Plants must grow to live. Any plant that is not growing is dying." Dr. Alex Shigosize> Unless there are nutritional issues, plants that have stopped extending and show no growth when they should be coming into a period of robust growth usually need repotting. You can usually confirm your suspicions/diagnosis by looking for rootage "crawling" over the soil surface and/or growing out of the drain hole, or by lifting the plant from its pot & examining the root mass for encircling roots - especially fat roots at the container's edge. You'll be much less apt to find these types of roots encircling inner container perimeter in well-aerated soils because the roots find the entire soil mass hospitable. Roots are opportunistic and will be found in great abundance at the outside edge of the soil mass in plantings with poor drainage & soggy soil conditions - they're there looking for air.

3) When the soil is so compacted & water retentive that you must water in sips and cannot fully flush the soil at each watering for fear of creating conditions that will cause root rot. This isn't to say you MUST flush the soil at every watering, but the soil should drain well enough to ALLOW you to water this way whenever you prefer. This type of soil offers you the most protection against over-watering and you would really have to work hard at over-fertilizing in this type of soil. It will allow you fertilize with a weak solution at every watering - even in winter if you prefer.

Incidentally, I reject the frequent anecdotal evidence that keeping N in soils at adequacy levels throughout the winter "forces" growth or "forces weak growth". Plants take what they need and leave the rest. While there could easily be the toxicity issues associated with too much fertilizer in soils due to a combination of inappropriate watering practices, inappropriate fertilizing practices, and an inappropriate soil, it's neither N toxicity OR the presence of adequate N in soils that causes weak growth, it's low light levels.

Is there any rule of thumb as to how often ... to remove and replace the old soil?(yes, I realize some soil mixtures last longer)

Yes - every time you repot.

Al

You know what works for me.
I potted many of my plants into Al's mix and,I will fill you in on what I do.:-)
What I do is I take the plant out of the origanal pot, then I hose down, yes, hose out all the old soil from the roots till it is barerooted. You would be amazed at how much old soil will fall out of the root ball. It is as if it gently melts away, like watching ice disappear as it melts.
Then I gently take the soil I make, Als mix, then tap some into the root ball before putting it into the pot. Then I put my plant into the pot and fill in the rest with Al's soil mix. It is easy, and it works for me. I hurt no roots, I break no roots, and they barely move while the soil falls out around them. I have great results with this technique, and I them thriving as we speak.
Al, also made a good point not to be overlooked...Stick the plant in shade for a few days until the plants revives from the change, this will surley shcok them more than a root job!
Also, Al is right on this too, right after you have transplanted them, they do seem to not take it well, but then, then, after a few days in the well airated mix.WOW. A flush of good growth!!
They seem so happy in their new fresh airated soil!;-)

Happy growing!!
:-)

I don't understand the logic of "manhandling" plants (for lack of a better term) when potting up.

Every time I've repotted plants and removed all old soil from the roots, many of my plants inevitably wilt, and over the years, quite a few have died from that treatment. They just never recover. If I lift the plant from the old pot with root ball and most of the soil intact and place it into a larger pot, and tuck new soil around it, I hardly ever have a plant go into shock and wilt, and possibly die. My question is, why is my situation so different that I can't repot the way you do without disasterous results?

Randi

Thanks, Mike.

Hi, Randi - Let me help you with a better term: "Root-pruning" :o) I'm teasing just a little, because in many plants the roots really CAN be manhandled with impunity. The logic is explained in my post above & has to do with the steady decline in plants over time. Potting-up, as opposed to repotting/root-pruning is a stopgap measure. The soil in the old root mass will calcify and harden, eventually restricting nutrient flow to to the above-ground parts of the plant - it's inevitable. As the plant's vitality wanes, insects, disease, or root rot sets in and claims the plant. Blamed, are the pathogens or an unnamed cause, when actually it was poor soil or lack of attention to roots that started the downward spiral.

There is never a day on this forum that someone isn't complaining or asking in a current thread about this or that problem. How many of these plants are lost unnecessarily? 95%+, I'd bet. What are the symptoms? - bugs, disease, general decline .... What should we imagine to be the most common and most likely cause? I'm not at all bashful about being adamant that it's poor soils and inattention to what's going on IN the soil - hands down, that's the biggest problem.

Here's an illustration: People at church think I'm some kind of miracle worker and bring me their dead/dying plants. I cannot remember the last one that died. I tell them to hang on until the weather is warm so I can keep the plant outside. I usually completely bare-root it and prune the roots hard. I repot it in a fast soil, fertilize it, and set it in the shade to recover. After it has started to grow well, I prune back the top & return the plant to the owner, who is invariably amazed. I'm not saying that to brag, because anyone can do it. All I do is follow a little plan & it works every time.

I'll say too, that plants are plants. There are some with idiosyncrasies that we need to be familiar with, but mostly, they react pretty much the same. If we allow that there are bonsai trees of the same species as your houseplants that have been passed down through generations for hundreds of years, it's difficult to imagine why we can't keep our houseplants alive for more than a few years before we discard them. The ONLY difference in the hundreds of years old bonsais and our houseplants is the soil and the attention paid to the condition of the roots. It's actually MUCH more difficult to keep bonsai healthy because of the small volume of soil they grow in and the adverse affects of being grown in shallow pots, but still they persevere, seemingly forever.

Here are some pics of how I pruned a scheff that someone from church didn't want & had given me. I'd posted these pics before, & a guy who was about to be married found the pics online & e-mailed me in a panic because he had killed 'her' scheff & wanted to know how to resurrect it. It was dead, so I offered him this plant. I can't remember if his GF called or wrote, but I shipped them the plant & she mailed a picture of it in tip-top shape a few months after it was shipped.

{{gwi:82237}}
An ugly plant, even before the work.

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a 'before' look at the root mass

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choose your weapons

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not being too gentle

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3/4 of the roots removed on this one

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bare-rooted

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recovery ward - recovery just underway

Joel's HP is a vigorous woody vine & can easily be treated in the same fashion. While the root pruning of your plants needn't be so aggressive as this, you can see that bare-rooting and root-pruning needn't be something to be feared, but rather another tool you can use to help keep your plants around for more than a few years.

Al

It looks like you repotted in the same pot. You cut away 3/4's of the roots. By my standard, that would be a bit over potted. Your roots must grow like crazy.

Toots - I probably did repot into the same pot. I realize that by your standards it appears that I over-potted, but your standards differ from mine because of the soil you grow in. If you must worry about over-potting, it can ONLY be because the soil you use holds perched water in a layer of saturated soil at the bottom of the container or above a "drainage" layer. Since I grow in highly-aerated soils with the bulk of the particles in the 1/16-1/8 size, heavily favoring the larger particles, and we know that perched water levels decrease as particle size increases, until finally, as particle size reaches just under 1/8" the perched water table disappears entirely, I need have no concerns about over-potting. Because these soils remain entirely unsaturated, I can grow the tiniest plants in huge volumes of soils if I prefer, and water nearly as frequently as I like w/o risk of anaerobic conditions in the root zone.

Roots do "grow like crazy" in any well-aerated mix. The higher the percentage of air in your soils the better the root growth/vitality and the better the o/a potential plant health. If roots didn't grow so well in highly aerated soils, we'd start cuttings in puddin' instead of perlite. ;o)

Take care.

Al

Al,,,hahahahahahaha..I couldn't help it..You probably shocked a few people on this site with those torture tools and the decapitation....Oh man..I needed a laugh. But you definately made a point and can prove that their is sucess in knowing your stuff..Thanks again for the wisdom in plant growing!!!

This is a great discussion, very helpful.

I have another question for you, Al. You report great results not only resulting from the fast-draining growing-medium that you use, but also from the radical root pruning that you practice. Okay, I want to ask about the root pruning...

At the risk of getting a bit off topic, have you found that you can apply the same (or a similar) approach in garden (non-container) situations? With the average decorative shrub or tree in a garden-soil-based situation, have you practiced root pruning with plants and had encouraging results in terms of vitality? (I realize one would have to do a lot of digging, but that does not scare me.)

J.

how do you know how much of the root mass to cut??

. . . have you found that you can apply the same approach to root-pruning in non-container situations? With the average decorative shrub or tree in a garden-soil-based situation, have you practiced root pruning with plants and had encouraging results in terms of vitality?

I do practice root-pruning on in-ground trees, shrubs, and other woody perennials but it has nothing to do with an attempt to increase vitality. I will root-prune these plants in preparation for lifting and transplanting. In fall, I often use a sharp spade to sever roots in the approximate circumference of the root mass I'll be lifting in the spring when I move the plant. Severing the roots forces the plant to grow fine roots close to the base of the plant so that when I lift it, I'm not getting just conducting roots, but fine, feeder roots too. This eases transplant shock & allows the plant to establish much faster. Obviously this is more important on trees & shrubs.

You can also use root-pruning to slow a plant down. If I had a plant in the landscape that was the perfect size in a perfect place, I might like to slow growth to enjoy it while it's perfect. I can help accomplish this by pruning roots to keep the stored energy contained in the severed portion from being used to produce more biomass.

We don't lift and prune plants in the landscape because compaction, soil collapse, and with unlimited room for extension, being root-bound are not issues.

I think you need to consider that root-pruning is more remedial and akin to preventive maintenance than it is stimulative. The remedial/preventive part comes from the fact that it fixes root problems associated with too many roots, severely compacted soil, soil collapse, and others. 'Preventive' comes from the fact that it prevents the steady decline of plants that might be allowed to languish in the conditions named, by correcting the conditions before or at the onset of symptoms.

I'm going to quote from a post about high-phosphorous fertilizers I just left on the container forum because there is a close parallel to our conversation in what I said.

Somewhere along the way, we curiously began to look at fertilizers as miraculous assemblages of growth drugs, and started interpreting the restorative effect (to normal growth) fertilizers have as stimulation beyond what a normal growth rate would be if all nutrients were adequately present in soils. Its no small wonder that we come away with the idea that there are Âmiracle concoctions out there and often end up placing more hope than is reasonable in them.

What I'm pointing out is that fertilizers really should not be looked at as something that will make your plant grow abnormally well - beyond its genetic potential . . . Fertilizers do not/can not stimulate super growth, nor are they designed to. All they can do is correct nutritional deficiencies so plants can grow normally.

Similarly, root constriction, collapsed/compacted soils, a high ratio of conducting roots to feeder roots are all abnormal conditions we subject our plants to. These conditions, which so often cause the abnormal, weak growth that is the stuff of so many woeful tales on this forum, rob all possibility of normal growth. Full repots, including root-pruning and a complete soil change, correct the abnormalities so plants can again have the potential to grow normally.

Al

how do you know how much of the root mass to cut??

As a general rule, the plants with built in vigor (genetically vigorous) that are also growing robustly tolerate root-pruning very well, but every once in awhile, a plant like bougainvillea comes along and spoils the rule - they don't tolerate root work well. Other than perhaps some of the palms & other monocots (and bougies) I can't think of a houseplant that didn't tolerate root pruning and/or bare-rooting well.

If you're concerned about how much to remove, start by removing 1/4 of the roots from the bottom of the root mass, bare-rooting, and then remove an additional 1/4 of the largest roots. If the plant tolerates it well, you can be more aggressive in the next repot. You'll learn by experience and as you gain confidence, you'll "just know" how far you should/can go.

I should mention that this procedure is most effective on plants with woody roots, which most quickly grow to be inefficient as they lignify, thicken, and fill the pot. Those plants with extremely fibrous root systems are easier to care for. For those, I usually saw off the bottom 1/2 - 2/3 of the roots, work a chopstick through the remaining mat of roots, removing a fair amount of soil, prune around the perimeter & repot in fresh, well-aerated soil.

Al