You will rarely see containerized trees grow old and maintain good vitality w/o attention to root-pruning. There are several reasons to learn root-pruning & I'll expand later if there proves to be interest or questions.

Almost all deciduous woody material tolerates root-pruning well. Most evergreens tolerate it well, but not all, especially if you are lucky enough to have 20 yr old or older plants. Some require some innovation to maintain a desirable level of vitality. More later.

In in situ situations, large roots serve only (ok, primarily) to anchor the tree. In containers, we can depend on finer rootage to accomplish this. Fat roots serve no purpose in container culture - other than to take up valuable space that might better be utilized by finer and more efficient rootage. So - cut the fat ones!

Deciduous trees can usually be bare-rooted before bud movement in spring with little worry. For nursery material, I start by sawing off the bottom 1/3 of the roots. With a Foggit nozzle (fixed brass fine spray attachment for hose) and a chopstick, I remove all the soil. For evergreens, I often divide the rootball into 4 imaginary pie-shaped wedges or quarters (as seen from above). I still saw the bottom 1/3 off, but I only remove the soil from the roots occupying 2 of the 4 wedges. This accomplished, I remove about 2/3 of the heaviest roots in the 2 wedge areas (this leaves all the roots in the other 2 wedges). Since deciduous trees are usually bare-rooted, I simply remove approx an additional 1/3 to 1/2 of the roots remaining after the saw work and soil removal.

Roots that are growing straight up or down are removed first, as are those growing back toward the center. I concentrate on removing roots immediately under the trunk as well. Roots are trimmed around the circumference to eliminate encircling. When finished, your goal is a disk shaped root mass with roots radiating outward from the trunk.

Work in shade and out of wind/sun. Keep roots wet while working. Hair roots can be killed quickly by drying out.

To repot: Place damp soil in container like a volcano, & place plant on top. Twist lightly to seat soil under trunk. Add soil on top of roots and work into roots with a chopstick. Occasionally tap side of container with hand to settle soil. When all air pockets are filled, water well and secure plant in container. This is important. Plants that are braced against movement reestablish in a fraction of the time of those that can move about. Place plant in bright shade until new growth is evident and them move to appropriate site.

Sounds complicated, but it is very easy and very plant-beneficial. By summers end, you should expect development of root-pruned plants to surpass that of counterparts in which root-pruning was not undertaken.

Intervals vary. Young trees can go up to 3 years in some cases before they show effects of being pot-bound or soil collapse. I'm pretty particular, so I keep a close eye on intervals and use a very stable soil for woody material. I can tell by looking at most trees, the actual year they were repotted or potted-up. Branch extension decreases as root vitality diminishes. This causes leaf bundle scars to become compressed or closer together. In years that you pot-up or repot, they really stretch out again before shortening in subsequent years. Just count terminal bud scars backward to determine repot years. Neat - huh? ;o)

Al

Thank you! Wow what an eye you must have developed...So when it comes to evergreen-type trees, you remove a PORTION of the total volume of roots, then bare-root only PART of the roots and selectively prune those you have bare-rooted, and thus leaving a good portion untouched.... to clarify, is this what you meant about some evergreen trees not tolerating root-pruning well and needing to be creative to maintain vitality?

My goals are to maintain some non-deciduous trees and plants--mostly citrus but a few others as well--in containers without having to increase pot size successively--which hasn't been working all that well. It seems that if one is willing to increase container size, it's not that difficult. But I've got one tree that is quite large and I feel management is becoming diffult. When it comes to maintaining size--or switching to a completely different media--it appears proper root management as you described is very important. [ For crying out loud there are potted citrus hundreds of years old in French orangeries--surely it's not impossible ;) ]

Yes, you have it, RJ. Next repot, you do the other half.

You'll have best results with nearly all trees if the soil is about 60-75% (often to 90% for some woody plants)mineral (Turface, crushed granite, pumice, Haydite, sharp gravel, very coarse silica sand are all possibilities).

Al

Awesome. Thanks.

Now that I have your attention :)...

This brings me to another scenario. I have recently acquired a new citrus tree, #5 container, that is not a *commonly found* variety. The problem is, it planted in soil that had a mix of 2 problems--it is lousy fine soil and it is compacted. Tightly. Concrete, if you know what I mean. (I find this grower often produces plants in this condition, but there isn't any other choices for me.) In the past, when I have tried to remove soil that is bound so tightly because I feel there is no real root penetration of water and fertilizer or I am worried about poor draining, the tree doesn't do so hot ( prolly root damage from nearly bare-rooting). However, I plan to move this tree in CHC's and this is probably akin to moving it into chipped bark orchid media or something equally *chunky*.

Now, if I don't try to take off a good portion of the concrete-like stuff, wouldn't there be potential issues with the abrupt transition between the compacted soil and rootball vs. the well-draining chunky mixture--which I would also describe as holding a lot of water as well as air ( kinda like little firm sponges, if you will, that take a LONG time to dry out beneath the surface). Citrus tree roots are very netlike, and hold that compacted soil tightly. I am wondering about the old nasty soil staying too wet up against the chc's. Would you just proceed as you outline above and stop thinking too much :) ?

And then there is the issue of contact with the new media. With a partially bareroot tree as above, when you move it into something with such a different texture (chcs, turface, lava rock, etc) and you have that netlike rootsystem, do you just wait for the roots to grow into the new media?--the replacement media clearly can't surround the roots the way finer particles like soil would be able to. If I were able to bare-root and really trim like w/ deciduous trees this wouldn't be an issue.

In all honesty I would love to grow in "rocks" like you are recommending: minimal compaction issues; probably not a lot of tipping over in the wind. But, where I live it's usually not very hot but is very very dry for half of the year--the trees would dry out really quickly, and I don't have time to water everyday.

Why "sharp" gravel?

Ok I will shut up now. TIA everyone.

Sharp gravel, with its irregular edges and points, creates good permanent spaces. Worn, tumbled, or smooth gravel can snug together. ALL of the materials mentioned by Al in the previous post are angular and sharp in their shape.

Old compacted soil in original root balls must be removed for trees to grow with maximum vitality. I have literally had to chisel soil from plants that had been put in the ground, "temporarily", in their nursery containers. This kind of compaction is very damaging to vitality and eventually causes death of the plant.

First, two distinct soil types in one container are going to cause root issues at some point. One soil type will either be too wet or two dry in comparison to it's counterpart. Hard to argue this point and it can be offered as support for developing a consistent soil and for bare-rooting appropriate trees at repot time and repotting in uniform soil mix.

Then, the effects of being root-bound are often not visible until the plant is in severe decline. Foliage may appear healthy for a few growing seasons while the plant weakens. Eventually, the plant may die from seemingly unrelated issues like insect or fungal attack, but the underlying cause is often a plant weakened by root problems. The first sign of being root-bound is reduced shoot extension. Your plant just refuses to stretch out. This is a sign of an inability to move water and nutrients to the canopy (or top of the plant) efficiently due to impaired root function.

So - potting up creates dissimilar soils in same container and potential rot issues. Here's what happens when you don't root-prune & only pot-up. The soil hardens/compacts & roots grow very large while they encircle each other in the original rot mass. The soil compaction alone is enough to inhibit the ability of the root to increase in diameter, the effect of which is the same as girdling the root. Also, the roots that are intertwined press against each other and create the same choking effect as encircling or girdling roots do at the basal flare. The most common symptom of restricted roots, other than reduced vitality and diminished shoot extension, is the death of individual branches on the tree. This varies by species. Some trees are able to move water and nutrients well, laterally as well as vertically; others (like Thuja) nearly have specific roots that feed major branches and move it pretty much only vertically (they actually have graphs drawn of this stuff). When these roots are compromised, branches lose vitality and quickly die.

Dorie (always) makes a very good point. Sharp, irregular particles don't compact and they create pores that retain air. I don't grow trees in rocks, but in a mix of about 2/3 irregular mineral particles and 1/3 pine bark. The particles are about BB size & the bark a little larger. The sharp and irregular mineral pieces also lend the extra advantage of promoting root ramification (division), which creates a system of finer roots - roots that are more efficient at water/nutrient uptake than the ones you should be removing. ;o)

Al

Rickjames: Tell me you watch Dave Chapelle... lol
It's the first thing I thought of when I saw your name ; )

"I'm Rick James, b!t@h"

(sorry-- I'm a big fan)

Amanda 'romando'

Al,

Ok, so that soil has got to come off, evergreen or not. Got a game plan now, thanks. You've been so helpful, I really appreciate it...Err, my plants probably will appreciate it also, as you may just have rescued some from the compost pile :)

Amanda,
fo' shizzle!
YEEAH!
WHAT?!

I thought the "Racial Draft" was hilarious.
TyroneBiggums isn't as catchy as a screen name, but was my second choice.

Thanks to all.

Would anyone advise root pruning on a clematis? I have several clematis in far too small pots due to a lack of space in the front yard (too much taken up by drainpipes and bikes). I was initially thinking of keeping the clematis only a few years and then passing them onto a friend with a big garden and buying new ones. However if I could root prune them I might get a bit longer out of them.

If you learn root-pruning techniques, do the pruning while the plants are dormant, and use an appropriate soil, you can keep them in a small container indefinitely. Witness bonsai that are many generations old and passed down when owners pass on or sell.

Al

Hi Al,

I had a quick question. What is the appropriate time to prune the roots of tropical evergreens? I have some houseplants that might need it, but is it too late to do it?

Thank you,
Anchita

Which ones? I do root work on woody tropical and subtropical plants in the month prior to their most vigorous growth. For me, that means early Jul or late Jun. You could probably do it with best results (quickest recovery) in early to mid-May.

Al

Thanks so much for your prompt reply, Al. I have a couple of Dracaena, a philodendron, a rubber plant and a few that I don't know the names of :-)

Regards,
Anchita

I would wait until late May to do the Ficus e. The others you can do almost any time now.

Al

Thanks, Al. I really appreciate your promptness and patience with my questions!

Regards,
Anchita

Al: I was discouraged from trying to do a daphne in a pot because it has a "very deep root system ". My husband just loves these and I can't grow it outside due to poor drainage and temperature. But I could grow it in my unheated greenhouse in a pot, with your soil mix. Can I root prune a "deep rooted" shrub like this and get it to be successful (and blooming) in a pot?

Thanks--
deb, or

Pay no attention to deep/shallow roots in containers. Shallow-rooted plants are that way because they require lots of air, which they find in the top layer of soil. Deep rooted plants require less air and can grow deeper in search of water & nutrients, but they don't have to; nor do they need to be grown in a particularly deep container. Either (deep or shallow-rooted plants) will grow well in a well aerated mix in a container; after all, the roots needn't go far in search of the water or nutrients you will so ably supply. ;o) Daphne is a very common container plant.

Al

Fantastic I feel much clematis root pruning coming on the next dormant season. Even after one season in 1ft pots some of my clematis (they are not all so punishingly treated but space is an issue for me) look a bit rootbound they really seriously grow rootstock like it's going out of fashion.