Why do some growers prefer to keep plants root bound?

exoticrainforestSeptember 2, 2010

Some of you know that I love to chase down the sources of horticultural beliefs. If you have ever spent time on any plant forum you know the common advice is to keep your plants root bound, or at least when you repot give the roots only an "extra fingers width" on each side the pot. My question is where do that advice originate? Why do we believe it? Is this really good growing advice or just an old wives tale? Are plants in the rain forest root bound?

I understand that nursery men prefer to start their plants in small pots and allow the roots to fill it before stepping the seedling up to a larger pot. My understanding is they do this in order to encourage a hearty root system first. But it appears some growers may have taken this advice to excess and always keep their plant's root bound. Should we always keep our plants in pots so small their roots are for ever crowded, or give them space to grow?

We always have new growers looking for good growing advice. If you have adopted a small pot policy please tell us why. If you are an experienced grower and prefer a tight pot method I would enjoy knowing the reasoning. Many of you don't know that I have written for years for a variety of magazines and I have another train of thought in this area. I am now working on a new article to explain about plant growth, a plant's need for oxygen around its roots as well as how to keep their root systems healthy. This discussion will help me to formulate my article.

I am here primarily to listen, not to offer my observations. If I find useful quotes I would like to be able to use them in the article. If you are new to growing, please chime in.

This post is now on 5 forums and I plan to combine the best responses into the final piece.




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rhizo_1 (North AL) zone 7

I believe that part of the reason that this is perpetuated is due to the type of potting medium so typically used (and abused) by what is probably the majority of hobby container plant growers.

These mediums are often very fine textured and slow to drain, creating a perfect environment for root rot if stagnant soil areas stay wet and mucky. Less soil volume=less opportunity for this to happen.

As far as professional growers go...the reasons are pretty simple, really. Laziness, lack of planning, lack of knowledge on the permanent damage they can cause to root bound plants. Lack of space and time have a lot to do with it, too.

    Bookmark   September 2, 2010 at 10:21PM
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You might try it on the orchid forum. Certain orchids seem to grow better when confined to small pots even with little media. Many are not rainforest orchids but rather plants which grow in harsher conditions, such as rock.

As it relates to dirt plants, I always thought under-potting creates a stress which in turn causes a plant to flower faster. You sacrifice size to produce better flowering. It inhibits root/green growth encouraging flowers. A small plant in a large pot will concentrate on root/green growth.

Overwatering can occur in any media, or lack of, such as with bare root orchids. Any plant which doesn't receive enough light and air circulation will stay damp causing roots to rot as well as fungal problems.

Underpotting can be very useful depending on what you are trying to accomplish such as bonsai or early flowering.

I played around this summer with typical annuals grown in very small pots. I was impressed how well the plants flowered and contained themselves in very small pots. Very pretty as their leaves grew smaller. Took more work but the results were interesting.

This is just my observation, nothing scientific. Try asking over on Orchids. You will probably get better answers.


    Bookmark   September 3, 2010 at 12:10AM
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greenman28 NorCal 7b/8a

Great question, Steve.

Here's an interesting Thread on the Myth of Under-Potting.
A good Thread, although it trends toward the disputative eventually.

Such is the tendency when old notions are shattered.
Humans are creatures of habit.


Here is a link that might be useful: Myth: This Plant Likes/Prefers to be Root-bound

    Bookmark   September 3, 2010 at 12:34AM
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Thanks everyone, and thank you Josh for the link. I am hearing all sorts of answers from different forums and private mail and that is my primary goal right now. I don't want to write an article about "what I believe", I want to do one about what people have accepted and why.

There has been a fair amount of analysis on this done in science and I want to bring that into the discussion as well. The eventual goal is to show people the options and why some approaches may work better than others but not try to force anyone to accept or dispute anything. Growers find different methods that work and now I'm just looking for reasons and answers.

Jane, the basis of what you say is well founded in growing but I want to also approach if it is all factual. Much of what we all have learned was passed down to us and some of it just isn't accurate even though it is accepted.

A lot of this has to do with off the shelf potting media and how little time is spent explaining how plants actually grow in nature. Many folks cannot believe a plant can grow in a home as it does in nature but my personal experience has led me to believe that isn't always true.

Thanks again! I mostly want to listen and not fuss with anyone. Regardless of what anyone accepts, I'd like to hear it.

Thanks everyone. I just want this to be a good discussion but we can try to arrive at answers at another time.


    Bookmark   September 3, 2010 at 1:26AM
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I just saw the article was started by Al. Thank you Josh, Al makes a lot of sense with his reasoning so this will be a fun read. I've found there are some very good minds on this forum and I'd like to see much more discussion about subjects of growing importance. Hopefully any rancor can be left on the sidelines.


    Bookmark   September 3, 2010 at 1:31AM
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paul_(z5 MI)

Rather surprised no one has mentioned the cost factor. Bigger pots mean more media and also less space on the grow bench. It also means higher shipping costs which means higher cost to the customer. Ergo using smaller pots saves the grower $, increases the amount of stock they can keep on hand, and helps "move" the stock by offering customers inexpensive plants

    Bookmark   September 6, 2010 at 5:40PM
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linda_schreiber(z5/6 MI)

I have a couple of comments. But my main question is at the end.

"If you have ever spent time on any plant forum you know the common advice is to keep your plants root bound, or at least when you repot give the roots only an "extra fingers width" on each side the pot."

I have never seen anyone recommend that you keep a plant
literally 'root-bound'... In so small a pot that the large roots are circling the pot, and having the root mass pretty much completely fill the pot.

But it's also true that more non-pros have killed plants from serious and stupid "over-potting" than any other cause other than perhaps persistent over-watering. Take a small plant, put it is a much bigger "pretty" pot with a lot of cheap potting soil, water it once a week, and the small, shallow plant roots are trying to survive in a desert while the bulk of the pot-soil is moist. I *always* advise people to pot-up very slowly... after making sure that I have looked at the roots, and that the plant is not root-bound.

I suspect that nursery staff start their plants in small pots because it eases time and labor, and reduces the expense and the watering, and allows them to toss cheap any that do not propagate or thrive. Those that do, they pot up a level. And perhaps again. But I strongly suspect that they hope to *sell* them before they become literally root-bound. And they don't, so things become root bound.

There are some plants that like their feet a little more constrained, while others want to grow wild. But are you saying the there is some folk-practice among pro-growers that it is somehow *good* to keep the roots seriously constrained?

I would be interested.

    Bookmark   September 6, 2010 at 9:21PM
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My son came home with a spider plant last May, and the instructions on the tab said to keep it in a small pot and only replant to a pot 2" larger than the current pot. I noticed that I got some growth, but a lot of babies off it. In Sept, someone told me that if you can see the root growing out the bottom of the pot (which it was, but I hadn't noticed), then it's time to repot. I put it into a bigger pot, and OH MY WORD! It's growing so fast and lush! So I think I'll keep putting it in bigger pots. But this is the first time I've ever kept a plant alive for more than a month, so take my comment with a grain of salt.

    Bookmark   September 12, 2010 at 12:45PM
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Rather than leave anyone that is interested in suspense I found a link on my site that can explain most of this.

Now, you don't have to read the entire page since some (perhaps most) will not be of interest. Just scroll down the headings and start with the part about rain forest soils versus the soil you buy and read down to and including the part on solving the problem.

I think many will change their minds about tight pots but if not, every grower has the right to choose the way they grow their plants. It is very true that nursery people use small pots for several very good reasons but afte the plant is well established it can safely be given a larger pot.

Back in a week! Have fun while I'm gone. If you are in Miami please join us at the International Aroid Society Show at Fairchild Tropical Botanic Garden on September 18 and 19!


Here is a link that might be useful: Soil and what kills many plants

    Bookmark   September 13, 2010 at 1:19PM
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Very well done, Steve. I enjoyed reading about the plant which sits in my office. It's in front of a north-facing window and has been there for 4 yrs. Seems fine, but I think I should try to repot it this spring.

Thanks for the great information,

    Bookmark   September 15, 2010 at 1:41PM
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Thank you Steve !

And by the way, my ZZ plant is doing great because of the info you provided me on it...

I can't wait to read your next article..Have a safe trip..:-)


    Bookmark   September 15, 2010 at 5:31PM
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maxygolf(z7b SC)

Azaleas I bought at the beginning of summer were dying so I dug them up and found they had roots so tightly bound they could not expand into surrounding soil and water could not infiltrate into the inside of the rock hard root ball. I tried soaking them to free them from each other which did nothing and then tried cutting it open with a knife but found that the mesh of roots were all very fine and could not be seperated from the medium, which seemed to be a hard substance itself.
I wondered if this was compacted coir they used to propogate the plant.
Has anyone else had this problem?

    Bookmark   September 15, 2011 at 8:39AM
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Tiffany, purpleinopp GardenWeb, Z8b Opp, AL(8B AL)

Maxy, sounds like peat. Nasty stuff. Whenever digging a hole for a plant, I use a long screwdriver or dandelion fork to make several deep punctures in the bottom of the hole to give the roots some easy places to penetrate and get going.

    Bookmark   September 15, 2011 at 10:29AM
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Maxy..First, when you dig a hole, 'in the garden,' the hole should be large enough to set the plant, amend soils, and cover roots.

Personally, I've never had this problem. After a perrenial/annual/tree is planted, it's important the soil is well-saturated. It doesn't matter what type of medium it was potted in at the nursery. Peat or otherwise.
(Sorry Purple, I disagree with you about Peat,) :)

Also, Azaleas are water lovers. That's one reason it's important the soil should be watered, 'deeply' immediately after being planted in the ground.

Another issue is your garden soil type. Does it contain a lot of clay? Sand? Azaleas prefer acidic soil. Did you amend soils before planting or place directly in the garden?

In far northern areas, where Azaleas and Rhodo's grow beautifully, gardeners use extra Peat blended with soil. Watch Victory Gardens or other garden plant shows. Especially shows where hosts travel to different states/countries.

I assume your Azalea was planted bare-root, not in a container.. Right?

98% of my perrenials and annuals were pot-bound when purchased. Some to the point roots were exposed w/o soil.
In these cases, I removed the plant from its pot, and hosed roots before placing in the ground. Hosing helps loosen roots w/o disturbing them.

Azaleas and Rhodos are intentionally root-bound since tight-fitting roots promote flowering.

Hose roots if you intend on placing back in the ground. While hosing, gently seperate roots with your fingers.
Place in soil that isn't hard so roots can spread. Toni

    Bookmark   September 15, 2011 at 4:20PM
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tapla (mid-MI z5b-6a)

It's not uncommon for plants that have fibrous root systems to become extremely compacted - often to the degree that it's ensured the plant will perish unless it's corrected. With fall coming on, you can probably correct the problem by sawing off the bottom half of the roots - no need to be particularly gentle, but don't go out of your way to be rough, either. Use a wooden skewer/blunt pencil/Popsicle stick to separate the remaining roots and 'comb' them outward from the center before replanting. Remove any large roots not emanating from the base of the trunk, and any circling/girdling, j-hooked roots, or roots growing back toward the center of the root mass.

Azaleas and rhodies are predisposed to grow very shallow root systems in situ and in the landscape because they do not tolerate wet feet well - they aren't water lovers, they prefer their roots where soils are only moist and aeration is plentiful, so plant only where drainage is good. Also, it's currently advised that planting holes NOT be amended with organic material or foreign soil, that new planting holes are back-filled with the native soil removed when digging the hole only, nothing more; and make sure that you plant with the basal flare at or slightly above grade.


    Bookmark   September 15, 2011 at 9:36PM
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