Do some online research under the topic "root washing".

Personally, this is something I would be rather hesitant to do with JM's, simply because they have such a sensitive root system. And would highly discourage doing it before the tree was fully dormant as is the preferred time for root pruning as well.

I've been in the nursery industry for years, with JM's kind of a specialty, and while there is ALWAYS the potential for containerized plants to be rootbound, I have found this NOT to be a huge problem here or with the growers we usually purchase from. In many cases, smaller plants offer less of a concern, simply because they haven't been around long enough to develop the problems. Bigger plants, bigger risk.

But even with a number of my own containerized JM's that I haven't up-potted soon enough, I have found that just gently massaging the rootball - not bare rooting/washing it or cutting through any roots - is enough to loosen the feeder roots to encourage their spread.

Girdling is another matter altogether and I might approach that differently :-) But again, I seldom see that with our maples.

I transplant a lot of Japanese Maples from pot to the ground at all times of the year here in the PNW. I never wash the roots clean. Just tease them a bit and plant. I cave the sides of the hole in and level with the topsoil from the hole and water well to establish capillary action so the rootball doesn't prematurely dry out.
Washing the roots clean might present more problems than it solves in my opinion.
Mike

GHG - here is a thread that goes into a fair amount of detail about root pruning and repotting containerized trees. Bare-rooting containerized maples is no problem - they tolerate it extremely well. You should also root prune and correct any potential root issues, like roots that grow back toward the center of the root mass, or grow almost straight up or down. Larger roots that cross, grow back toward the center of the root mass, are potentially girdling or encircling, or are j-hooked should also be corrected asap. Ideally, you want the root mass to consist almost entirely of fine roots, with no or very few roots growing directly under the trunk. They should radiate evenly & horizontally from the same ht on the trunk, and quickly branch into finer roots. This is the top of a trident maple I layered to remove the old (and very ugly) root mass and replace it with a new root system:
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You can still see the wire I used to constrict flow in the phloem so photosynthate & auxin would collect in the tissues immediately distal to the wire tourniquet. href="http://s26.photobucket.com/user/afassezke/media/repots005-1.jpg.html"; target="_blank">{{gwi:6332}}

Maples respond very well to even severe root pruning if you do your repotting in spring just before onset of bud-swell. It's pretty common for me to remove up to 90% of the roots from trees just exiting the quiescent state that follows dormancy . Root pruning and subsequent repotting is the only thing you can do to eliminate the limitations imposed by having allowed the tree (at any point) to reach a state of root congestion that finds you able to lift the root/soil mass from the pot intact. Once that state of root congestion has been allowed to occur, your plant's potential is permanently limited unless the root issues are corrected by root pruning and planting out out or repotting. Potting up or planting out alone cannot eliminate the limitations. It might allow the plant to grow a little closer to normally, which you might interpret as a 'growth spurt', but in fact what you are seeing is the plant growing in what is only a partial return to what would be normal growth. You might as well call any improved growth after potting up as evidence the tree was indeed growing under the limiting effect of root congestion.

After root pruning a trident that previously resided in a 5 gallon nursery can:

Al

This post was edited by tapla on Mon, Aug 12, 13 at 14:11

Thank you for all the info and links. This was exactly what I was needing. I'm surprised to hear that people don't find many JM's pot grown and root bound. I've found so many and from numerous "good" nurseries. The only source that sends me trees that aren't root bound at all is Diana at Topiary Gardens but those are young trees. Most of my larger trees had some issues with roots. I've got quite a few that still need planting or repotted. I bought Vertree's big book of maples hoping it would help with potting/pruning/planting and although it has beautiful pictures it didnt give me the information I was looking for. I appreciate the advice given, especially Al with those pics. It helps a lot. Thanks again :)

Hello Japanese Maple friends: I radically attacked a Japanese Maple yesterday before planting (15 gallon) and was shocked at the root system. I am sending the 2nd one I have back to the nursery, mainly because i am locating a nursery that doesn't have this problem. Over the long term, What I did to the roots, pruning badly kinked ones, and ones that would later strangle the trunk system. I literally washed to get all the existing soil out of the root system so there would be a better root to existing soil scenario. I read a couple articles that I don't know if someone has read or not, but at least it started me on my way to locating less problem trees with strangling root systems, and also be more confident in planting any tree that is terribly rootbound. My experience with this whole matter was because I really want a healthy tree, and so if it doesn't make it I'd rather know now than a few years down the road.

I don't know how to add a link to this Garden Web, but if you want to learn more google an article written by Linda Chalker-Scott; Ph.D., Extension Horticulturist and Associate Professor,
Puyallup Research and Extension Center, Washington State University, "The Myth of Collapsing Root Balls"
âÂÂBalled and burlapped root balls must be left intact during transplantingâÂÂ

I'm searching a nursery out of town now that uses a different system of growing and establishing trees after delivery to them from an actual Japanese Maple business called Heritage Seedlings as bare-root trees. Hey I've really wanted to learn, and not just take for granted.

Another article:
Research on planting container-grown trees
offers practical tips for enhancing long-term health
by Tom Tyler

Take care all,
Cynthia

I buy smaller plants, because they don't have the issue and given a typical plant about 3-4 years older, they'll adapt so much faster that they'll usually catch up and pass an older plant with those issues given 2-3 years of good culture.

Given that...I also don't disturb the rootball without any evidence that I need to, when I unpot it to transplant.

If your trees, at any time during their development, get to the point where you can lift the root/soil mass from the can/ pot intact, you can be sure that the trees' growth and development will be limited from that point forward, even if planted out, unless you get into the root mass and fix the congestion by removing all or almost all of the soil and pruning the problem roots. That's why potting up, rather than repotting ensures limitations.

Initially, there may not be obvious evidence that there is a problem, but when you start seeing smaller leaves, and shorter internodes or shorter distances between leaf bundle scars, you're seeing the first evidence of the effects of root congestion.

The "growth spurt" you think you see after potting up isn't really a growth spurt at all. It's the tree temporarily rebounding to a point somewhat closer to normal growth, which gives you a hint at how limited your tree was by the stress of root congestion.

Al

If your trees, at any time during their development, get to the point where you can lift the root/soil mass from the can/ pot intact, you can be sure that the trees' growth and development will be limited from that point forward, even if planted out, unless you get into the root mass and fix the congestion by removing all or almost all of the soil and pruning the problem roots. That's why potting up, rather than repotting ensures limitations.

Initially, there may not be obvious evidence that there is a problem, but when you start seeing smaller leaves, and shorter internodes or shorter distances between leaf bundle scars, you're seeing the first evidence of the effects of root congestion.

The "growth spurt" you think you see after potting up isn't really a growth spurt at all. It's the tree temporarily rebounding to a point somewhat closer to normal growth, which gives you a hint at how limited your tree was by the stress of root congestion.

Al