Repotting a Large Collected Water Elm

by Evan Tylor Pardue

It’s repotting season this time of the year here in southeast Louisiana, or is it repotting season yet? It’s really hard to gauge what the weather is going to do here to be completely honestly. A few days ago it was 80 degrees mid day and then the next it was 38 degrees in the morning. To follow that up, it rained for three days in a row making the humidity outstanding when it reached 75 and the sun finally came out.

I’m sure you’re getting the point here. Louisiana is all one crazy climate and it seems to change each year when we’re tapping our foot waiting for Spring to actually come. I’m writing this post in March, on a sunny day. Really it’s a beautiful day being that it really never got above 68 degrees. (Why is he going on so much about the weather) Regardless of what is going on temperature wise, our bonsai are not worried too much about that. What our trees are looking for is the length of day to gradually increase in the next coming month. As the sun begins to set later and later in the evening, there will be more and more opportunity for our trees to catch the sunlight.

Plants are truly opportunistic and given the right conditions they can be triggered to begin growing anytime of the year. They will grow given these couple of situations: the length of day is getting longer and temperature is raising slightly; or if they have undergone some type of damage. Spring is the gentle signal for the tree to start stirring from it’s slumber while we are standing over it just waiting to rip into it’s root system.

Wait slow down, why do we have to be like this. Can’t the trees just wake up slow without us intervening?

Yes and no. The “damage” we will do has all the good intentions and that is to free up the root system of broken down organic material that are void of nutrients. These areas of expended material could be broken down pine bark or sections of dead roots. In the case that your tree grew vigorously over a few seasons, you may be removing the excess of running roots that are pushing against the sides of the container.

So here’s the point. Spring is the soft trigger for new growth and our repotting is a hard trigger. So if both are happening at the same shouldn’t the tree grow that much faster? Depends if we are mindful of what we are trying to achieve in the repot.

Are we trying to revamp the vigor in our tree? Are we trying to reduce the root mass to get into a shallow container? Maybe we are working with a raw stock plant that is root bound and trying to reset the root system for bonsai container life.

It’s situational and it’s all based off of the when the opportunity presents it’s self.

Here’s the opportunity, this water elm’s buds are swelling. This is the signal we’ve been waiting for! The picture blow is showing the only extended bud on the entire tree thus far.

The water elm I’m about show in the series of pictures was collected by Zach Smith from Lake Catahoula. He did an excellent job working the roots and doing the initial potting. It was repotted shortly after Doug acquired this tree and was potted in our GoodScience soil mix. That was roughly 2 years ago and now it’s my job to repot this tree from a plastic training pot to a nice unglazed ceramic container. It has grown very vigorous the past two seasons and is very, very root bound.

So let’s get this tree inside and slip it out of it’s container. I prefer to use a flat blade tool or what I like to call a “tree spatula”. Why? Because you should use the thin blade to slip in between the wall of the container and the root system to remove the soil on the sides of the root ball. Removing this quarter inch of soil frees up more space then you can imagine. Then I use my “tree spatula” to get under the roots like a pancake and flip it out of the container. You could also call your flat blade tool a “treehorn”. Get it like a shoehorn? I also call changing the container out “changing the tree’s pants”. This supposed to be fun. Take the stress out this and believe you’re not going to kill your beloved tree. With the proper procedures in place you can increase your successes with sound practice. Also, have fun.

Chloe has the time of her life while I’m doing this type of work. Notice the thrill in her eyes as I left the tree from the container.

So here’s the top of the root mass after peeling back the moss growing on top of the nebari (Japanese word for “surface roots”). There is actually way more to the nebari buried underneath. The roots don’t just fill the container, they push the tree up and out. When all the space is used up like this the only other option for the roots is to stack on top of the surface.

I use a Chinese take out chop stick for this process. This isn’t something you shouldn’t rush through because you could rip and shred the tender roots. We’re not skateboarding here, we’re repotting a plant so ease up and take it slow. The chop stick has more give then your metal rake tool and sections of the chop stick will wear away before causing significant damage to the delicate roots right on the top. Another tip, remove soil at a 45 degree angle as apposed to jamming the chop stick straight down into the roots.

As seen in the previous picture, I uncovered the beautiful nebari hidden underneath. Exposing this base didn’t even require any root trimmed yet. For those who are terrified of hacked away at the roots, we are only removing 20% in the repot I’m preforming on this water elm. Now let’s look at the bottom.

Geez Louise! Now that’s what I’m talking about. Yes, I am happy to see this on this particular tree. This is a good sign as the tree has produced A LOT of healthy fibrous roots. The whole point of reworking a root mass like this is to get those thick tapping roots out of the root ball and cut them back to get the tree to “back bud” fibrous roots. The more fibrous roots we have, the better the chances we can get into a shallower and wider container to start creating the illusion of perspective. The thick roots I’m talking about are the bigger orange-ish roots on starting to constrict the root mass. The roots have filled the container and now these “runners” are extending out in search of more space to fill with more roots. It’s our job to reset this system and encourage new growth just like the top of the tree with it’s shots and branching. We are increasing the trees ability to suck up more resources and in turn produce thicker foliage mass and a wider energy distribution.

Using the “meat” hook to get in and gently pull the knots out of this dense root system. Notice the soil that fell away. This section of the soil was becoming inaccessible to the roots because of how fast the roots were sending “runners” around the interior of the container. Water elms are capable of growing roots at an alarming rate just like an actual elm. Planera aquatica is the Latin name but they share a lot of characteristics with the Ulmus family. They can grow roots really quickly and extend shoots just as fast. They are treated the same as other elms when it comes to repot intervals. Repot water every 2 years as necessary, if you don’t the vigor will reduce noticeably.

After clearing out the over sized roots and broken down sections of soil that just fell away I got down to this lovely root spread. That split you’re seeing up the middle is where a heavy surface root was removed in collection. The tree just needs a little help getting useful roots to grow in that area instead of thick “runners”.

The picture above is a directly under the main trunk of the tree. This is really important that we can see this part of the tree on a deciduous piece of material. It’s where the original tap root was and it has healed nicely. From this spot underneath the trunk there should be a nice radical selection of roots all the way around the tree.

Absolutely. Beautiful. This pleases me. After removing all the matted roots and getting a nice exposed nebari, tree’s image has changed dramatically. Time for the new container, time for a fresh pair pants!

That’s lovely. Not the final container, just a nicer container. This tree has issues with catching a lot of wind and toppling over. The ceramic is much heavier then the previous plastic container. Also this look kinda of tells me that it should go into another rounded edged rectangle pot in the future. Reason being is that this tree is very feminine. The bark is smooth and the lines of the trunk and branches are slightly moving outwards into it’s open broom shape. There aren’t any sharp edges to it’s form and the foliage mass on water elms do not get really dense in appearance. The leaves are very small even before reduction and have a dainty look to them. Overall, this is a solid step in the right direction and the container can be changed with each repot as we see necessary.

The pot is prepped with mesh screens and tie downs. The soil is spread evenly on the bottom of the container and a mound of soil is built up in the middle. This mound is where the opened up section directly underneath the tree will go. I place the open space directly on top of the mound and push down and twist gently to help get the soil up into this area. The last thing we want is an open air space in the roots that would allow fibrous roots to dry out and die. Also we have no real way getting this much soil up in there otherwise.

Now we tie down the tree by catching the two strong surface roots on either side of the trunk to bound it to this container. Wind should be the least of this tree’s concerns for now on.

The base looks so much bigger and the taper has greatly improved. The bark is starting to peel and there’s a lot of character developing in this tree! I will give a follow up to this in my next blog post so you guys can see first full flush of growth. I’m really looking forward to it!

Hope this helps anyone with questions and worries about repotting season this year. Shot me an email at evan@underhillbonsai.com if you have more questions or want to set up a repotting session with me.

Cheers,

Evan Tylor Pardue

Nursery Manager