Plants never thrive when they are potbound

Ohiofem(6a Ohio)July 5, 2012

Interesting research from Germany tells us what many suspected: Plants never thrive when they are potbound. Read about it in BBC Nature News:

"Plants grown in pots never reach their full potential, images of their roots show. A medical imaging technique called magnetic resonance imaging (MRI) has been used by researchers to capture plant pot root snapshots. The pictures reveal that the roots 'sense the size of the pot' and restrict the growth of the plant."

Here's an MRI of plant roots:

Here is a link that might be useful: Read more here

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Tiffany, purpleinopp GardenWeb, Z8b Opp, AL(8B AL)

I couldn't agree more, and that's compelling evidence. I've started using 5-gallon buckets my honey can get at work. Haven't gotten a pic added to that thread yet, but put a Sans in one the other day, maybe a week ago. Time will tell...

So often people post pics of plants with yellow tips and I think the correlation between the roots reaching the edge of the pot and the yellow leaves is so direct and glaring. Never have I had a plant not improve after removing all of the old soil and manicuring the roots. Even if it goes back into the same pot. Roots are either growing, or the plant is stalled. I'm convinced.

I would like to see someone use the MRI in conjunction with monitoring drainage and root progress (not just size.) It seems to me that the roots don't really need a ton of room, just maintenance to keep them fresh and active. The big ones seem to serve as mainly anchors and plants in pots usually make more of them than needed, and very often in "wrong directions" from what I've seen. Trimming them doesn't seem to do any harm, but the regrowing of them is what seems to make the foliage part really kick it up a notch.

    Bookmark   July 5, 2012 at 12:05PM
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tapla (mid-MI z5b-6a)

There's a current discussion about this article over at the container forum at Dave's. I get the sense that there was a LOT lost between the interviewer and the interviewee, because the description of the experiment leaves more questions unanswered than it answers.

We know with certainty that tight roots restrict growth and vitality, but if roots "sense" the bounds of the container and stop growing, that would be a revelation, and it would seem that the article should center around that fact, but it mentions it only briefly.

My experience is that in some cases, when roots are not constricted and the temperature is favorable, I can usually get BETTER growth in containerized plantings than in plants in the ground, and this persists until root congestion becomes limiting or root temperature enters the picture as a limiting factor.

It's never been my experience that roots grow to the edge of the container and then stop, or somehow reduce their growth rate. When using heavy soils, roots often fail to colonize the center of the soil mass due to an inadequate air supply. Instead, they often run to the perimeter of the soil mass in profusion & circle where aeration is best - where soil shrinks away from the inside wall of the pot. In well aerated soils, unless root congestion is severe, roots tend to colonize the entire soil mass more or less evenly. When root congestion is severe, even in well-aerated soils you'll see a tendency for roots to circle, but this is almost always at the pot bottom, which is very interesting because that usually doesn't occur in heavy soils.

Many of us have always understood that root congestion is never a good thing, from the plant's perspective. No plant "prefers" to be root bound OR grown in a tight root situation. We can use the stress of tight roots to make our plants do tricks, but the tricks are the plant's unhappy response to stress, so there is always something to be given up in exchange in the form of lost potential for growth and vitality.

In wish I knew more about the experiment and that the article was done better, but it's still very interesting.

Thanks, Robin. Hava good weekend! I watched some guy on TV eat (I think) 67 hotdogs yesterday - made me queasy just thinking about it.


Here is a link that might be useful: More about the myth that some plants prefer tight roots

    Bookmark   July 5, 2012 at 12:27PM
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I don't know if anyone gardens in the open here, but if you do you are probably aware that all plant roots in a thriving garden are restricted, by their neighbours. Even not very rampant neighbour plants constrict the roots of plants they share the ground with; plants are used to being 'bound' even if not in pots. Exceptions would be isolated cacti or other such plants in deserts, maybe, or lone trees on mountains.

    Bookmark   July 5, 2012 at 2:10PM
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Ohiofem(6a Ohio)

As Al noted, there appears to have been a lot lost between the journalist who wrote the article and the scientist he interviewed. Specifically, the idea that plant roots "sense" the boundaries of their containers is pretty startling. I did a little more digging and think I've found the scholarly article about this research. Here is a rather lengthy passage that I think inspired the journalist's over reach (emphasis mine):

If neither nutrient or water availability nor higher temperatures can (fully) explain the pot size effects on photosynthesis and growth, it could be that root confinement per se may cause growth retardation, with reduced photosynthesis as a consequence. Root growth is known to respond directly to impedance. Impeded roots stay shorter whereas the initiation and growth of side branches increases (Bengough and Mullins 1991; Falik et al. 2005). Furthermore, Young et al. (1997) showed that within 10 minutes of increasing the impedance to root growth, leaf expansion rate is reduced. This suggests that some kind of signal may regulate shoot growth when a large proportion of the roots are impeded. The actual signal for such a response remains as yet unknown. Possibly a reduced sink strength of the root system could cause a direct negative feedback on photosynthesis (Paul and Pellny 2003). Alternatively, a specific root-shoot signal is involved (Jackson 1993).

A crucial point in the evaluation of the lastly discussed option is knowledge on the actual distribution of roots within the pots. Although the vertical root distribution is relatively easily measured (Price et al. 2002; Suriyagoda et al. 2010), analysis of the horizontal distributions is more complicated. Using non-destructive magnetic resonance imaging (MRI), we followed the root development of Hordeum vulgare L. and Beta vulgaris L. plants over time in three dimensional space. Representative nuclear magnetic resonance (NMR) images of root systems at the end of the experiment are shown in Fig. 3. We calculated the percentage of roots that was located in the inner half of the soil volume, furthest away from wall and bottom and the percentage of roots present in the outer 4 mm of the pot. Only 20-25% of the root biomass was in the inner part of the pot (Table 1), whereas ~50% was found in the outer 4 mm (20% of the total volume). The proportional distribution remained remarkably constant over time. Hence, if these observations have wider validity, we conclude that a relatively large fraction of roots is close to the edge of the pot, where unfavourable environmental conditions, for example, large temperature fluctuations and impedance of the pot wall may negatively impact growth.

This is from an article in Functional Plant Biology called "Pot size matters: a meta-analysis of the effects of rooting volume on plant growth." Follow the link below if you want all the details.

Here is a link that might be useful: Pot Size Matters

    Bookmark   July 5, 2012 at 4:55PM
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Tiffany, purpleinopp GardenWeb, Z8b Opp, AL(8B AL)

OK, I admit, I don't want to read that whole article, Ohiofem, but skimmed it as much as I could until I went completely cross-eyed. (And thanks for sharing the link to it!) I don't think it mentions at all what is IN THE POTS. It seems critically important to me, the texture of it, not so much what substance(s) of which it is comprised.

It is the plant mass per unit rooting volume that is relevant rather than pot size per se. - Conclusion section of above-linked article. When one considers the volume of knowledge necessary for success with Bonsai, it makes sense that it would be easier for a container plant novice to have a better chance of success with a larger pot. But to give the pot size all of the credit is incomplete without giving some info about the media used for the experiments. To be "well-drained," air pockets are necessary. Varying particle size and large, rough particles make this possible. So that caveat seems important to attach to the "use a bigger pot" advice.

Forgot to mention above, those MRI images show much sparser roots than most of my plants grow (which is solidly, throughout the pot.)

    Bookmark   July 5, 2012 at 5:36PM
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Tiffany, purpleinopp GardenWeb, Z8b Opp, AL(8B AL)

    Bookmark   July 5, 2012 at 6:08PM
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I suspect the type or species of plant would play a role in this as well. Many gesneriads grow in rock crevices (Saintpaulia ionantha for example) and seem to languish and succumb to root rot easily if even slightly over-potted. They will usually not bloom until their roots have filled the available space. It seems that the article is generalizing a bit. Plants are too diverse to have much in the way of all encompassing rules.

    Bookmark   July 5, 2012 at 6:43PM
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tapla (mid-MI z5b-6a)

It just seems like a tremendous amount of effort to reach a conclusion that we've all known for a very long time - tight roots = reduced growth. It would have been nice if they'd have gone a step further and included the reduction in vitality that accompanies the stress of tight roots as well.

"If neither nutrient or water availability nor higher temperatures can (fully) explain the pot size effects on photosynthesis and growth, it could be that root confinement per se may cause growth retardation, with reduced photosynthesis as a consequence."

I too, find it remarkable that no consideration was given to air:water relationships IN the soil, or just soil quality in general as a viable explanation for reduced photosynthesis/growth. Still, it will be interesting to link to the article the next time a certain occasional visitor makes his regular appearance to argue that tight roots have no significant impact on growth, even if it does seem like something of a puff piece.

Hows that Eugenia, Robin?


    Bookmark   July 5, 2012 at 8:06PM
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stonesriver(6B Tennessee)

"Plants are too diverse to have much in the way of all encompassing rules."

Amen. Gesneriads do not grow/bloom well unless potbound. This is firsthand observation as I have been growing them for more than 35 years and now have 250+. With all other conditions the same (including size), strep in a 2.5" pot showed more growth and earlier blooming than strep *from same leaf* put into a 4" pot. Four-inch pot took 10 months to reach the same stage as 2.5" pot in three months. Both were pot bound when they bloomed.

Lovely photos, purple. Always enjoy your shots.


    Bookmark   July 6, 2012 at 12:17AM
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tapla (mid-MI z5b-6a)

They may bloom better, but I'd bet that if you put an AV in a very large pot in a soil that ensures good root health and compare it to a plant in a very small pot in the same soil, the plant in the large pot will win every time (all else equal) insofar as the rate of increase in mass is concerned. Send 2 rooted cuttings from the same plant & I'll do the comparison ..... I think there is no reason to think that one plant out of many thousands would react differently to tight roots than all the rest and grow better with restricted roots.

Many growers feel their favored plant requires highly specialized care, when actually almost all the plants commonly discussed on this forum all want the same thing. I treat all my plants the same way - same fertilizer same watering habit, and they all do well - maybe exceptionally well, depending on what standard we use. I even grew AVs in the gritty mix and used a fertilizer with urea as the N source (MG 12-4-8) just to prove the point - with pictures.

Sure, there are ways to tweak care, and tricks to get plants to dance to our tune, but with growth as the measuring stick, and excluding cacti but including succulents, probably 99% of all the plants we are likely to grow in containers will do very well with the same care.

If a plant seems to grow better when grown under tight root conditions, it's very logical to suspect the soil is a limiting factor - that tight roots are a requirement, necessary so that air can return to the soil faster to undo the limitations to root function posed by soggy soil conditions. This doesn't really MEAN the plant grows better under root bound conditions; it means that tight roots are less limiting than soggy soils ..... at least that's what we're hoping. Essentially we're settling for the lesser of two evils - in consideration of growth, which is represented by the amount of increase in dry mass.


    Bookmark   July 6, 2012 at 7:30AM
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stonesriver(6B Tennessee)

I have thought long and hard over whether to respond to the above post. However, I've grown African violets and other Gesneriads for 40 years and actual experience brings more proof than theories. Now, I'm not saying the above poster and the study are wrong in all cases; just specifically when it comes to Gesneriads.

Unless asked, I would never be so presumptious as to tell someone what they are doing is not to the benefit of a plant. However, since it has been brought up, I must say the photos of African violets in "gritty mix" show plants that, while acceptable specimens, are terribly overpotted and certainly not grown to their full potential. And I don't mean as show plants.

Anyone can generalize and theorize but people who actually grow Gessies and grow them well (I include myself and snappyguy among that number) know they thrive and bloom best when pot bound. Why anyone who doesn't grow or has only grown a few of them would argue that fact is quite beyond me.

Below are examples of the African violets I grow (AVs are Gesneriads). They are all pot bound and don't seem to realize they're not thriving so please don't tell them. :-) You can click on the photos for larger images; I apologize for the poor quality of the images in advance.


Ness' Cherry Confection; a chimera

Pookie; a chimera

Shirl's Cranberry Confection; symmetrical foliage is not from any manipulation on my part.

Sora Purple Clouds on 18" x 20" chair seat to show size

Wrangler's Jealous Jewels

A different "Pookie" showing pot size vs leaf span

Cool Touch; a chimera

    Bookmark   July 6, 2012 at 10:45PM
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stonesriver(6B Tennessee)

I realized the only AV I've seen grown in a "gritty mix" was on this forum; I just saw it numerous times. So sincere apologies to anyone who might have grown them to their potential but not posted photos on this or the African Violet Forum.


    Bookmark   July 7, 2012 at 2:17AM
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tapla (mid-MI z5b-6a)

My contention has never wavered from specifically focusing on the impact tight roots have on growth, and I haven't generalized or theorized - just wanted to be clear about that. ;-) Your AVs may LOOK better and BLOOM better, which are arbitrary measures of what it means to "grow" better, and more accurately is a measure of how well the plant pleases the grower. Growth, specifically, on the other hand, is a measure of the increase in the dry mass of a plant; that is, how much the plant weighs, sans water. There is NO good reason to believe that Gesneriads are unique among the many thousands of other plants we containerize that exhibit increasingly slowed growth as root congestion increases.

That I'm not an aficionado of Gesneriads has nothing to do with my ability to analyze or think logically, and it's not necessary that we be bus drivers to know what makes the wheels go round and round. If in fact, Gesneriads grew better in tiny pots, you can be sure people would be using them and kin to highlight that unique trait by growing them in thimbles and bottle caps. The fact is, you all pot Gesneriads up as the plant gets larger because to NOT do so simultaneously ensures decline and stalled growth.

If a challenge was issued for anyone to start a leaf cutting in a plastic medicine bottle that holds an ounce or two of soil, and to grow that cutting as a healthy plant for several years in the medicine bottle, would ANYONE take up the challenge? I think not - especially if there was a comparative plant with it's feet in increasingly larger volumes of soil as the root system increases in mass, and whose growth rate the plant in the smaller container had to surpass to validate your projected results. Why? Because Gesneriads are no different than other plants in that tight roots negatively affects growth and vitality.

Finally, we can be absolutely certain that Gesneriads are negatively affected by tight roots through reasoning alone. Imagine a container with a given volume. Even if that container was chock full of healthy, functioning roots, the volume of roots will STILL dictate how large the top of the plant CAN be. Once the top has reached the maximum volume the roots will support, and the container has already also reached its maximum volume of roots, it's impossible for mass to increase. Roots can't grow + top can't grow = NO growth, which should be logical enough for all to see that tight root conditions does affect growth negatively. No theory here - just facts. The only way I can see any wiggle room in that scenario is if someone claimed that the plant grows better (please remember the definition of growth) for a little while with tight roots and then it doesn't grow better anymore with tight roots, which is probably stretching things a little too far.

If a plant APPEARS to grow better when grown tight, it's almost always because a soggy soil has the potential to limit growth. Growing the plant tight eases the impact of soggy soils because the smaller volume of soil allows air to return to the soil faster. In this scenario, it's NOT because roots are tight that the plant grows better, it's because the grower has eased the limitations of a poor soil by introducing the limitations of tight roots - essentially trading one limitation for another and gambling that the tight roots are less limiting than the soggy soil.


    Bookmark   July 7, 2012 at 10:10AM
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Ohio...It's true, many plants need large pots to grow, to survive.

Plants that grow large---trees

For a tree-like/bush plant to reach its full capacity, obviously roots need space.

Many of us collect plants that grow 25' and taller in-ground.

To name a few grown as house plants: Dracaenas, Ficus and Pachypodiums. Grown in-ground said plants have enough room and then some, but in pots, we're limited. Moreso for people in cold climates who cannot keep plants outdoors year round.

Since we're discussing house plants..none of the three plants mentioned will ever reach full maturity, 'containers' opposed to the height and width of in-ground trees/bushes.

What happens to these plants once roots fill the largest container manufactured?

Small Plants

Linda mentioned African Violets.

Potting an AV, from mini to standard, in a large container, would definately kill this Gesneriad.
AV roots are shallow. They are not meant for large spaces--in their native habitat or pots.

Ohio, perhaps you've never researched or have grown AV's. Pot an AV in a 10" container, 'despite soil/medium'..see end results.
I guarantee, not only will an AV not flower, crown rot would be at high risk, and plant will eventually expire.

Miniature succulents, another example.

Flowering Plants.

Not all, but some flowering plants need tight roots to bloom. This is no myth. When plants are forced into bloom they're under-potted to promote flowers.
Like African Violet, repot in a large pot and good-bye blooms.
Other examples are Azalea, Cyclamen, Schlumbergera, Zygo, etc.

Caudex and Jade

In order for certain caudex plants to 'fatten,' pot size should remain on the small side. When roots fill a container, repotting a size up is essential.
Unless, of course, the variety is tiny.

Growing Jades as Standards do well in small, tight-fitting pots. This is a man-made skill, since Jades are naturally bushy, tall wide trees/shrubs.

PS: Check out the African Violet Forum... Suggest, 'to AV experts,' repotting AV's in large containers. lol. Toni

    Bookmark   July 7, 2012 at 1:12PM
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tapla (mid-MI z5b-6a)

No one is suggesting anything, or being critical of anyone's growing methods. No one, especially me, cares if what grower A or B does is not in the plant's best interest because the grower's interest is much more important than the plant's. Few on these forums are more guilty than I of doing things with plants that are technically not in their best interest, yet the result is usually a very attractive and often unique specimen. In many, many instances, I like the way a plant grows with tight roots better than it grows with room for roots to run, but the grim fact is what I like doesn't matter. The plants still grow better with plenty of root room. So there is no confusion, the plants grow faster - they increase their mass at a faster rate when roots are unrestricted. This really is elementary stuff, which is why the the people doing/reporting on the study that started the thread are essentially being accused of having a keen grasp of the obvious.

The question is, "Do tight roots impair the growth of Gesnariads" - nothing more than that. The answer is unequivocally yes, just as the study that is the original focus of this thread suggests by its conclusion.

Straying here: I'm sorry, but there is no plant that technically needs tight roots to bloom. The added stress of tight roots may promote earlier bloom or more prolific blooming, but if these plants reach sexual maturity, have enough energy, and it is the appropriate time in the growth cycle, the plant will bloom. There is no one constricting the plant's roots in the fields/forest/gardens ..... yet the plant manages to bloom quite well with no added stress, but let's not widen the scope of this question to include a wide variety of other topics. The fact is, there is absolutely no reason to believe Gesneriads are different than any other plant in the way their growth rate is affected by root constriction. If anyone truly believes differently, then I suggest they take up the challenge of performing the experiment with 2 leaf cuttings of an AV or any Gesneriad. One stays in 2 oz of soil and the other is potted up as it grows. Does anyone really think the plant constricted to the medicine bottle will grow faster/larger than a plant eventually potted up to a quart of soil?

Toni asks, "What happens to these plants once roots fill the largest container manufactured?" The answer is easy - growth and vitality go into a tailspin and the plant declines unless the condition is corrected.

From her writings, I know that Ohiofem is well versed in how soils work. I'd like to hear what she thinks about the prediction that if she were to plant an AV in a 10" pot despite the medium, that it will not flower and will eventually expire ... and that the plant will be at high risk for crown rot. My contention is, of course the plants will flower, and that it depends almost entirely on the soil/watering habits as to whether or not the plant will be affected by crown rot or expire from over-potting (root rot), and that in highly aerated soils (like the gritty mix and the 5:1:1 mix, there is little chance of any problems related to fungal infections, like crown/root rot.

Again, let's try to stay focused and not keep adding other topics to disagree on so the original topic of contention is lost in the fray. There was only one area of disagreement, now there are several.

I hope that made sense and wasn't too repetitive - no time to proof it - company arriving soon and the shower beckons me.


    Bookmark   July 7, 2012 at 2:07PM
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greenman28 NorCal 7b/8a

for caudex plants to grow fat, swollen trunks, the plant should be in a larger volume of soil.
Our resident caudex expert - Caudex1 (aka Keith) - has said this many times: if you want your
caudex plants to get big, you bury them and give them free root-run. Then, once the caudex is large,
you pot them and raise the trunk a little bit to reveal the thick base.

For big, fast growth, free root-run is required.


    Bookmark   July 7, 2012 at 3:33PM
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Ohiofem(6a Ohio)

I haven't grown African violets in a very long time. I used to try to grow them in African violet potting mix and they always died. But it so happens that I picked up one at my favorite garden center about three weeks ago and planted it in gritty mix. The pot it's in is almost as wide as the plant, so this may be a little experiment. So far it has continued to put on new blooms and seems healthy, but I think I should give it a few months before making any conclusions.

I will say that I have had many plants bloom after being put in larger pots with gritty mix, including clivias, plumeria, goldfish plant (a gesneriad), and bougainvillea. I even had an amaryllis bulb bloom in midsummer after transplanting in June against all advice. That same bulb bloomed again in January.

    Bookmark   July 8, 2012 at 7:00PM
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stonesriver(6B Tennessee)

"The fact is, you all pot Gesneriads up as the plant gets larger....."

If you're referring to seedlings or plantlets, this statement is a little disingenuous since the need for potting up any plantlet/seedling is a no-brainer. However, if you're speaking to mature plants, you are wrong; it is not a fact. (I would caution against using "all" in any statement unless you actually *know* "all" do what you contend.) Of course one can grow a Strep or an AV in a 10" pot. But that hasn't anything to do with the fact nothing bigger than a 4" pot is *necessary* to reach their full potential and they reach this potential when pot bound. Your contention that I'm wrong is, well, wrong.

I wasn't going to, but I felt I should explain this one final time as my purpose is not to argue but to enlighten and educate and because I realize you don't grow or know about AVs or Streps and their needs. And that's all I'm gonna say about that. :-)

On another note, do you have an updated photo of your African violet you could post? And, you shouldn't need someone else to send you plantlets for any experiment. You should be able to do it with your own AV by taking a leaf and putting it down. When big enough to separate, and using equal plantlets, put Baby A in a 10" pot and Baby B in a 2" pot. Move Baby B to a 3" pot when the leaf span is 9" and to a 4" when 12" then let it get pot bound. You could post bimonthly photos. If I understand your logic, Baby A should do better and grow faster than Baby B. Luckily, this wouldn't be a time-consuming project and take up very little space. (BTW, from looking at the photo it appears there is pollen spill on the blooms; an indication your AV has thrip.)

Good luck in your experiment.

Chem: I agree, AV soil spells death for African violets. I use 2 parts coarse perlite to 1 part Metro Mix (never with coir).


PS: AV and Strep sizes are not limited by their containers; they are limited by the variety. I grew an Apache Rainmaker to over 36" in a 4" Volkmann squat pot. I did have to use leaf supports.

    Bookmark   July 9, 2012 at 12:34AM
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tapla (mid-MI z5b-6a)

We're not talking about an arbitrary definition of what it means to 'thrive', we're talking about the effect of tight roots on growth, growth being measured as an increase in the dry mass of a plant. It's not at all disingenuous to suggest that if the plants grow better with tight roots, that the smaller the volume of soil used the better the plant should grow. In view of the study's conclusion, and that every nurseryman/greenhouseman knows with certainty and acts on the fact that tight roots = lost growth potential, the burden of producing something other than anecdote that points to the fact that Gesneriads are unlike all other plants, in that they put on growth faster when pot bound, is on you. I can point to the study on this page and the effect on tight roots on all plants, while you can say the study is flawed or it didn't include Gesneriads. Let's forget about my contention for the moment then, and focus on this from the study: "Plants grown in pots never reach their full potential, images of their roots show. A medical imaging technique called magnetic resonance imaging (MRI) has been used by researchers to capture plant pot root snapshots. The pictures reveal that the roots 'sense the size of the pot' and restrict the growth of the plant." It didn't say "plants other than Gesneriads", it just said "plants", which is all encompassing.

Opinions may well be divided along political lines, but it's not logical to abandon the idea that tight roots = lost growth potential because of what one person, or even 20 people think. IF Gesneriads are unique among plants in this regard, I would think growers would be very interested in producing scientific evidence relative to that unique trait, evidence that clearly notes the rate of growth in Gesneriads increases as the plant becomes more root bound; and I would also believe that information would be available in a format that excludes anecdote. You may find anecdotal evidence because growers who concentrate on particular plant types often consider their plant of choice to be very unique, but I suspect anything scientific will be a challenge.

Finally, in the post script you mention having grown a 36" plant in a 4" square pot. I too, have spent a great deal of time growing very large plants in very small pots. My experience indicates that had you used a 6" pot, the plant might easily have grown to 42 or perhaps even 48" within the same time span. IOW, that you're able to grow a large plant in a small pot is not indication the plant prefers a small pot or grew to its full potential with roots restricted; and it would be an error in logic if in fact that was the contention.


    Bookmark   July 9, 2012 at 8:28AM
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rhizo_1 (North AL) zone 7

OMG! That AV mix is the worst! It should be labeled AV Muck! I swear that it must be made of 'swamp muck ', the ooze usually labeled as sedge peat on the bag. Sedge peat IS swamp muck. It's the stuff of Tarzan movies. Wasn't there a Lassie episode or three where Timmy got stuck in some AV soil and began sinking? Lassie was told to "...go get help, girl ", but she knew intuitively that she didn't have time to race over hill and dale, under the barbed wire, across a rope bridge over the ravine, stave off slathering wolf packs and spitting cobras (wait, wrong show) ....rattle snakes, chew her leg off after getting caught in a bear trap, and save a child who had fallen into the well. Then, once she finally made it back to the farm and explained carefully to Paul and Ruth what had happened and where Timmy was sinking into the AV muck Lassie knew that those bums weren't going to budge until they had a nice lunch and a piece or two of gooseberry pie.

SO! She stays with Timmy, searching the nearby woods for just the right branches and vines to push out to 'her boy ' to pull him to safety just before his nostrils sink below surface of the muck forever.

And they expect people to grow African Violets in that stuff?

    Bookmark   July 9, 2012 at 8:54AM
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I am having mixed feelings on this post so I would like to share my opinion.
I have many plants that do not do well unless pot bound.
African violets
Spider plants
They may not thrive per say pot bound but it helps them bloom and most of the time will not bloom unless pot bound. I am thinking as "thriving" as growing new growth and blooming so maybe they may be half right about their research.

    Bookmark   July 9, 2012 at 7:19PM
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greenman28 NorCal 7b/8a

Stress produces blooms in many plants....basically, the plant "thinks" it is going to die,
and so it blooms/fruits in a bid to carry on the species.

Humans often respond similarly to early childhood abuse with early onset of sexual maturity.
A human *can* bear children at a very young age, but I think most will agree that it's best
for the human if the physical system is allowed to develop at a more reasonable pace.

Stress, in both animals and plants, produces results. But those results aren't necessarily the
best measure of "vitality," or health.


    Bookmark   July 9, 2012 at 8:57PM
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tapla (mid-MI z5b-6a)

I'm more than willing to concede a lot of points in this discussion. I'm sure Linda knows a whole lot more than I about what it takes to bring along an attractive AV. I readily admit that stressing the plant by keeping it root bound is almost certainly the preferred method of ensuring an attractive plant with lots of blooms.

My experience with AVs is limited to 2 plants I bought in the fall, stuck in the gritty mix, over-wintered under lights, and fed with a fertilizer that drives its N from urea. I have no interest in AVs, the only reason I grew the two as I did is because I was assured it wouldn't work. Half way through the following summer I gave the plants away because I'd proven the point & had already lost interest.

My inexperience might place me well below expert status on the ladder to AV growing stardom, but that doesn't mean I'm fresh off the boat when it comes to plant physiology. I understand how plants grow and what impedes growth. I have a very scientific mind, but if what I think I'm observing doesn't square with what I know of science, the first thing I reject is my own observations. It should be no surprise that I'm equally willing to reject someone else's observation as well, when it doesn't square with science.

We are getting a lot of other issues confused with growth. Growth isn't looking pretty and having a maximum number of blooms, and a thriving plant by one grower's standards could still be missing out on a good deal of growth potential. I'm perfectly willing to concede that a better LOOKING plant is possible if it's grown tight. There is only 1 area of disagreement, and that is whether tight roots promote faster growth in any plant, but specifically Gesneriads. There is no scientific reason to believe that Gesneriads are unique among plants, regardless of what one person or 20 thinks when there are thousands on thousands of plants whose growth is negatively affected by root congestion.

There are MANY growers like Alavoneluvhoya who feel their plants seem to grow better when root-bound, and are readily willing to attribute the better health to that condition - even in the face of the fact we KNOW tight roots retard growth. Please consider the more plausible explanation is, with the soil she is using, growing the plant tight may be necessary to prevent the root problems associated with the soil she is using. Tight roots means that favorable volumes of air return to the soil faster after a thorough watering - which eases the limitations imposed by the poor soil. Because the soil problem is eased by tight roots doesn't necessarily mean tight roots are desirable. They are STILL limiting, just not as limiting as the soggy soil's effect on root function. If you feel your plants grow better when root bound, you probably need to take a close look at what they are growing in. There is no need to trade one limitation for another in an attempt to improve growth.

This doesn't mean you still can't be happy with a plant growing under limitations. ALL our plants are suffering some limitation, no matter how hard we try. What's important is knowing how to look at the problem and not so readily jump to post hoc conclusions or confuse coincidental relationships with causes.

"I have a nice looking plant that is 10 feet tall with lots of blooms in a 6" container, therefore the plant likes being root bound" is exactly the same logic as, "I TRIED to grow a 10 foot tall plant with lots of blooms in a 6" container but it died before it got 2' tall, therefore 6" pots kill plants." Neither are logically valid.

No one is trying to take away the tool of keeping plants root bound to get them to bend to your will. The only contention is that tight roots slow growth in all plants. In containerized plants, if you're vigilant, you can really start to note the slow down at about the point where the root/soil mass can be lifted from the container intact.

Most of what I just offered is contained in a post I wrote back in '10 (see below). You might find Steve Lucas's comment offered on 9/3/10, as well as the rest of the commentary to be of interest ...... the text too, of course. ;-).


Here is a link that might be useful: More here

    Bookmark   July 9, 2012 at 10:10PM
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