It's time to vote on our 2017 photo contest! Vote for your favorite photos of the year here!

MRI show that pots limit plants

Everett, WA(Zone 8a)

Some scientists used MRI (magnetic resonance imaging) on 80 different species of plants and "discovered" what most gardeners already knew: pots limit plants' growth when roots reach the pot walls.

I wonder if I could get federal funding for determing whether or not water was wet?

To be fair, maybe these MRI images will tell someone something we did NOT already know.

For example:
- - "Even the largest pot was not large enough not to limit growth."
and (paraphrasing) :
- - 'plant roots quickly reach the edges of pots and concentr5ate in the outer half, hardly using the inner half.'

I always suspected the second observation, and figured it was why people pot up gradually from the current pot to slightly larger pots, rather than drop the seedling into a huge pot when pricking out.

Bay City, MI(Zone 6a)

I'm not sure if the article was poorly done or the experiment poorly performed. There are a number of factors that come along with pots that have the potential to limit growth and vitality, chief among them is the medium the pot is filled with. From the information offered, the question is begged, WHY did the roots run to the edge of the pot and stop? In my mind's eye, I can see a water retentive medium with roots wanting to grow near the inside wall of the pot because that's where the plant's access to air/gas exchange is best. How often have we seen a container with roots that wrap several times around the inside of pot walls at the interface between the inside of the pot and the outside of the soil mass, with the center of the soil nearly devoid of roots; this, because of a poor, water-retentive soil? The soils I use are always completely and evenly colonized by roots at repot time, indicating the entire soil mass provides a healthy environment that keeps roots happy. Obviously then, the tendency is not for roots to stop growing once they reach the barrier of container walls.

Generally speaking, growth and vitality begin to be notably affected at about the point where the root/soil mass can be lifted from the pot intact, and simply potting up at that point doesn't alleviate the stress associated with tight roots in the original root mass. Repotting on the other hand, which includes a change of soil and correction of the root congestion through root pruning, resets the ontogenetic clock and restores plants to their full potential for growth and vitality, the influence of other potentially limiting factors not withstanding.

In a perfect world, we wouldn't need to be concerned with things like high root/soil temps in containers, or poor air:water relations in the media, but in practical application they are significant considerations and capable of limitations even greater than root congestion. I'm sure there had to have been much more information that might have been included in the article, but who knows ...... and I do agree it seemed like a lot of trouble to go through to confirm what we already knew.


Everett, WA(Zone 8a)

>> The soils I use are always completely and evenly colonized by roots at repot time

Ah hah!

>> correction of the root congestion through root pruning, resets the ontogenetic clock and restores plants to their full potential for growth and vitality

I've always been timid about removing roots, but I'll reconsider that the next time I pot up a root ball that's 100% roots on the surface.

Somewhere in, MD(Zone 7b)

I can't help but wonder if they've missed something else, besides the obvious "What sort of medium were the plants growing in?". Why did they choose only barley and sugar beets to test? I've not done enough container-gardening to give my own general observations of roots, other than lemon grass in pots on my front porch. When I dig out the old to replace with new, I also, like Tapla, find a root system that is evenly dispersed throughout all the soil, not concentrated in any specific area(s).

There simply must be more to that study than that one little article disclosed. I'd be very interested to read more about that study.

Bay City, MI(Zone 6a)

Here are some before/after pictures of plants repotted so you can judge for yourself whether or not plants are able to tolerate root work. Keep in mind that many of my plants are specimens I've worked on for 20 years or more, so it's unlikely I'll do anything I think puts them in jeopardy of succumbing to the after effects of the work.


Thumbnail by tapla Thumbnail by tapla Thumbnail by tapla Thumbnail by tapla Thumbnail by tapla
Bay City, MI(Zone 6a)

A ficus .....


Thumbnail by tapla Thumbnail by tapla
Everett, WA(Zone 8a)

One spot mentioned that 80 species were tested. I didn't even look for the original article - so many of those sites are pay-per-view.

Just guessing: they were like kids with a shiny toy: "what can we do with this MRI that will get us published somewhere?"

If they weren't really gardeners, or farmers, they may not have giv en much thoguht to the growing medium. "I dunno - soil or something".

Or it might have been a reasoned choice.

Hmm, I don't see any link to a paper ...

"The findings have been presented at the Society for Experimental Biology's annual meeting in Salzburg, Austria."

At least one of them owns some houseplants:
"Lead researcher Hendrik Poorter, from the Julich research institute in Germany, told BBC Nature that as soon as he saw the results, he re-potted all of his houseplants."

"Dr Poorter's colleague Dagmar van Dusschoten produced the MRI scans"

I found the meeting with Google, but didn't immediatly find their Proceedings offered for sale or free.

I would love to see a time-lapse video of the MRI - maybe beforfe, during and after the pot was flooded to drowning for 60 min utes. Watch the root hairs, then the roots die back and start tol re-grow.

Too bad drowning doesn't work like root pruning, and re-start the clock!

Al, thanks for the photos of the root massacres! I guess it is safe and even good for them. But I'm even a sissy about pruning branches. But ya gotta do what works, not what feels comfortable!

This message was edited Jul 3, 2012 9:06 PM

Somewhere in, MD(Zone 7b)

Good morning. =)

I did a bit of searching last evening, and all I could find were several (upon several) articles just repeating the one you shared here, either in whole or bits thereof. Nothing new, and nothing mentioning the growing medium. I conclude that this is no conclusion at all, sorry. It certainly is interesting, but warrants much more info in order to be able to draw any reasonable conclusions.

I am quite certain that I have never done any root pruning like Al has, however, I sure am bold about cutting roots of new purchases before I re-plant them (into containers or otherwise), and thus far the only things I have had troubles with is Columbines... but, I hear they don't like transplanting very well anyway. Typically, I only remove about the bottom 1/3 of the roots, and then just "massage" the rest of the roots loose from the soil blob and then spread 'em out into their new home. (that's a technical term, by the way; 'soil blob'.) ;)

Bay City, MI(Zone 6a)

"Doing something" about tight root masses of bedding plants and plants in larger containers you're going to transplant can be extremely important to future growth/vitality. Many of us have planted root bound bedding plants, only to have them languish w/o growth for the entire growth cycle. If you can lift your plants from the cell pack or pot w/o the soil wanting to fall off the roots, they're too root bound to plant/transplant w/o giving up potential growth vitality.

I literally rip the bottom 1/2-2/3 of the root mass off the plant, and then tease the remaining roots apart. For larger plants, I use my fingers (3" pots & larger) to tease the roots apart by working them up into the center of the roots (this is AFTER tearing the bottom of the root mass off) and then outward, but for cell packs I use a nylon tool I made specifically for that purpose to tease the roots apart after tearing the bottom of the root mass off. This doesn't hurt the plant at all (witness the pictures above). I do it to every plant I pot in containers, year after year, without a hint of a problem.


Thumbnail by tapla Thumbnail by tapla Thumbnail by tapla Thumbnail by tapla Thumbnail by tapla
Somewhere in, MD(Zone 7b)

Utter and complete drool-worthy beauty there, Sir! **applauds loudly**.

This just reminded me, I am embarrassed to say, I think I forgot to remove roots from my Clematises when I put 'em in their planters out back, EEK!!!! This would explain their languishing, to be sure. Would now (this time of year) be an ok time to do it, or would it be best to wait 'til the Fall?
On the other hand, I am happy to report that I did whistle while I worked with my gardening saw on the roots of the other climbers I stuck in the giant whiskey barrel out front today, as well as the Coleuses that I re-potted. I will be looking forward to their new growth with joyous expectation! =)

Everett, WA(Zone 8a)

>> articles just repeating the one

I guess "news" has fallen on hard times, re-reporting what someone said that someone said". I'm just assumning that the "Proceedings" of that conference would cost triple-digits.

Better to spend the money on bigger pots and better mix! Al is giving better advice than the "newsy" articvles did. The article doesn't say much more than "if you do it worng, the pot really restricts the plant".

Al is showing that if you do it RIGHT, you can get great results with pots that don't look very big to me.

I'm about to launch some 5-gallon buckets for Sun Gold (?" Sungold?) cherry tomatoes.

Somewhere in, MD(Zone 7b)

Mmmmmm, sounds like a yummy endeavor, I wish you much success!! =)

Everett, WA(Zone 8a)

Thnak you, it be only my second year trying to grow tomatoes. Last year was my first, and I didn't expect ANY to ripen.

But, as usual in the garden, the plants surprised me. Stupice did fairly well, but lost all flavor after one cold night. The Sun Gold stayed tasty.

And happy_macomb just pointed out that McMaster-Carr sells 3x3 mesh galvanised steel hardware cloth (for screening a few cubic feet of pine bark mulch). The "thin wire" variety is relatively cheap, $1.23 per sq ft. But I'm trying to find out what the shipping cost will be!

I think it's cute that they call the flimsy variety "easy to form".

Somewhere in, MD(Zone 7b)

I'm completely unfamiliar with hardware cloth.. but, ... correct me if I'm wrong here, but doesn't the word "cloth" indicate that it's **supposed** to be "flimsy"? Maybe not, and maybe I'm just showing my ignorance here. ;) I think I've seen it in our local True Value, but I may be mistaken. I've only ever looked at the different types of screening and cloths there, never had any hands-on experience with any of them.

Bay City, MI(Zone 6a)

Chain-link fence is also referred to as 'fabric fence', so go figure. ;-)


Brooksville, FL(Zone 9a)


Just love the step by step pictures and your planters as always are beautiful.


Everett, WA(Zone 8a)

>> but doesn't the word "cloth" indicate that it's **supposed** to be "flimsy"?

Not really - as with people, it takes all kinds. "Hardware cloth" usually means woven, welded for extra strength, and galvanized.

You've probably seen 1/2" galvanized hardware cloth (also called wire mesh).
The bigger the hole, it seems, the thicker the wire, and the stiffer the cloth.

I have 1/2" and 1/4" welded galvanized hardware cloth, and both are stiff enoguh to play ping-pong with.

I have some 30 mesh and 60 mesh (stainless steel wire) that are almost as flimsy as window screening made of fiberglass or aluminium wire. Floppy.

In this case, the 3-per-inch mesh came in two different grades, with different gauge wire and different prices. The wire that's twice as thick costs 3 times as much.

I'm sure the 16 gauge wire would last longer than 21gauge, but I'm cheap and willing to pre-screen the bark fast-and-rough, maybe twice, before I use the 3-per-inch wire cloth gently.

"easy to form" 0.032" wire diamter (21 gauge AWG) $1.23 per sq foot

other, tougher: 0.063" wire diametr (16 gauge AWG) $6.61 per sq foot

Somewhere in, MD(Zone 7b)

Chain link fence is also referred to as "fabric fence"... get outta town, really!? I've never heard that before, honest! LOL!!!!

Wow, I am always learning so much here!! And Mr. Corey, thank you for that explanation, it makes sense. See, I really was just showing my ignorance! =) Hmmm... the more I think about it, the more it really does make sense.. thinking about my "emery cloth" that I use to sand down wood... it's called "cloth", however it certainly is anything but flimsy or floppy! =)

Never too old to learn something new. Thanks guys! =)

Everett, WA(Zone 8a)

There are some super-whiz-bang computer "buses" that they call "switched-fabric buses" ... I think they are arrays of fiber-optic links ... for when ONE fiber-optic bus isn't fast enough.

But I'm also happier calling things like cotton flannel "cloth" - good for wicking mositure and in a pinch can be used for diapers. I was thinking about shredding some cotton into beds that did not seem eager to share water around fairly ... but there must be better solutions.

These were taken while sc reening wood shreds (not bark shredds). I had uprooted some low juniper tol make more rasied beds, and wnated to shred the wood before composting it.

There is
1/4" hardware cloth (woven, welded, galvanized)
1/2" hardware cloth (also WWG)
1" chicken wire (flimsy twisted wire)
~ 3/4 steel shelving, thrown away where I work.

Thumbnail by RickCorey_WA Thumbnail by RickCorey_WA
Somewhere in, MD(Zone 7b)

Oh my goodness, they throw away that shelving where you work?? Wow, that's some really useful stuff!!! I'm glad to see that you rescue it and put it to further use. :)

Everett, WA(Zone 8a)

Oh, yeah. OH yeah! Oh, YEAH!

I keep hoping we'll throw away an entire shelving unit, but no joy.

My fvallback would be haunting the dump, recyle station, or the used-appliance second-hand store for wire racks from ovens or very old refrigerators.

Somewhere in, MD(Zone 7b)

My Darling DH (redundant, I know, but there really is emphasis on the "D"), whose birthday it is today by the way, (shameless plug! LOL!!!), brought home from work some really wonderful metal shelving units a couple years back, and we've got a bunch of them up in the basement, they are soooooooo helpful!!! They're rather like these "industrial" ones. I LOVE them! =)

They were re-arranging storage space and had gotten new shelving, so these ones were going in the dumpster. NO WAY! =)

Thumbnail by speediebean

Post a Reply to this Thread

Please or sign up to post.