Brian,

There are several methods you can use to root prune your tree:

1) Using a saw or knife, cut the bottom third off the root ball. Next, cut an amount equal to about 20% of the diameter of the container off all sides. Using a pair of chopsticks (I find bamboo chopsticks work best) remove the remaining growing mix from the roots. Pick out the remaining roots so they radiate from the base. Trim any roots that extend beyond where you made the cuts on the root ball. Also, cut out a couple of the thickest roots.

2) Using a pair of chopsticks, remove the growing mix from the roots. I find it is easiest to start from the bottom and work up. If the growing mix has compacted, it may be necessary to also from the top down until there is a meet somewhere in the middle. Generally, at the beginning it is easy to remove the growing mix. However, there is more compaction in the middle of the rootball... so it will get more difficult to remove the medium as you go along. Once some point is achieved, it will become easier to remove. Once all the growing mix is removed, comb out the roots with the chopsticks. Next, find a couple of the thicker roots and cut those out. Then cut the remainder to length by gathering all the roots underneath the tree (think ponytail) and cut. Alternatively, if the tree is small enough, turn it upside down so the roots hang downward (I also find it is easier to comb the roots out when the tree is upside down (think of someone bending over to comb their long hair), and trim to length while spinning the trunk of the tree.

3) Cut the bottom third off the root ball. Next cut two pie shaped wedges equaling about a third of the volume into the growing mix. Remove the cut outs. Put the remaining root ball into the container and add fresh growing mix. Repeat the procedure every year.

Once the tree is bare rooted (1&2), partially fill the container with new growing mix. I like to fill mine so that when the tree sits on top of the mound, the basal flair sits about 1/2 inch below where I want it. Comb out the roots so that they radiate down the mound of growing mix. Add more growing mix and work the roots through it with the chopsticks. The container may need tamping along the outside to help eliminate and large cavities. Once enough growing mix has been added so the container is at the desired level, gently begin pulling the trunk of the tree up. At the same time, insert one of the chopsticks into the growing mix under the tree. Move the chopstick in and out while at the same time making small circular motion to force the growing mix into the cavity created when the tree was pulled up. Afterwards, tamp the side of the container again to make sure all cavities are filled.

If the tree has come from a commercial nursery and has not been bare-rooted or if the tree is severely root bound, method 1 maybe the best bet. Although, one should still expect some severe compaction in the interior of the root ball. Last week, I bare rooted a tree in NJ which is 7' tall with a trunk caliper of over 2" and has spent at least the past three years in a 3g nursery container. It took me about three hours to bare root it using method 2. However, if I had used method 1, it wouldn't have saved me too much time (most of the work was done on the interior) and I wouldn't have had enough root mass to support the top of the tree.

If the tree has been recently bare-rooted, more than likely method #2 will be best since the root ball will probably fall apart without much prodding from the chopsticks. Also if the tree is being moved up to a larger container and needs more of its root mass than would be left by method #1, use method #2.

Method #3 is employed when the tree is large and in a large container.

I would suggest repotting as early as possible. Whenever you expect your temps not to fall below 30oF anymore and the highs are above 50-55oF is a good time. The sooner the tree is repotted, the more time it has to establish new roots before top growth begins.

~james

Thank you James for the detailed answer.

I will print it so I can study it further.

One quick question --

The Fig trees I have (still in the garage from winter time) do already have a lot of new leaves forming - So I assume from the last sentence of your reply I should not do anything this year and should wait until next year when the condition you specify (below) is met:

Whenever you expect your temps not to fall below 30oF anymore and the highs are above 50-55oF is a good time... before top growth begins.

I guess I should have mentioned the timing is somewhat subjective. The reason for root pruning improve conditions for new root growth. New roots are more efficient in transferring moisture and nutrients up into the tree. The root pruning process increases available space by removing larger less efficient root. The fresh growing mix provides the porosity to allow the flow of moisture and fresh air into the root zone. If there is some pressing reason for root pruning now, I wouldn't rule it out. However, if there is still space for new root growth and the growing mix hasn't collapsed, you could wait.

I mentioned the tree I root-pruned/potted up last week in NJ. It had just broken dormancy. Another one I root-pruned last week also had small brebas on it. They would have had a difficult time going another summer in the containers they were in. The one was so compacted, I had a very difficult time getting it to take water last year. Most of the water would run down the sides of the container. Because the trees had already started to break dormancy, I didn't prune the roots as hard as I might have otherwise. I am expecting to be bare-rooted next year as well (hopefully I will get to them earlier) and remove a few of the roots I left behind.

The reason I like to repot as early as possible (in Houston, between early Dec and early Jan) is so the roots have a chance to reestablish themselves before top growth resumes. I have found that as few as three weeks makes a huge difference in the trees (the small to medium sized ones) ability to keep itself upright when the winds hit the leaves. If you decide to do it now, make sure you stake your tree to prevent the wind from tipping it over.

~james

James
What will be the disadvantage of removing the old soil mix by soaking the root ball in a big water pot and then gently shaking up and down to remove the mix. I thought this should be easier than using the chopsticks.

Depending on how tightly the growing mix is packed... tired arms.

For the trees I have had for a while, it is not necessary. Most of the growing mix falls off easily, and the rest can be combed out quickly. Most of the trees I have picked up at nurseries have been too compacted to use water effectively. After some of the growing mix has been removed and the roots loosened up a bit, shaking the tree (whether or not in water) will allow some of the growing mix to fall out.

I had forgotten to mention water in my early posts. I have found that if the root ball is too dry, the roots become brittle and I lose more during the bare-rooting process. If the root ball is water logged, it adds too much weight. Not only does this tire out the arms when holding the tree, it puts added strain on the roots connection to the trunk. I normally water a day or two before I plan to remove the growing mix so that it is moist at that time.

Most of my trees are in Houston. The high humidity allows me to take my time with bare-rooting without worrying too much about the roots drying out. In more arid environments, the roots can be sprayed with a mist of water every so often to keep them moist. I have (in an experiment to kill RKN) left a tree bare rooted for two hours on a day that was warm, dry, sunny and windy. The tree survived.

Also, a shake in a bucket of water is useful after all the growing mix is removed to clean off the roots. This makes inspection easier. It is surprising how much some components of growing mixes look like RKN when they stick to the roots.

~james

Would you advise this same procedure for citrus in pots? How about other trees? I have a bay laurel I am trying to keep in a 15 gal and it is getting huge! How about pomegranate? It's great advice and I can't wait to try it next year.