Alder Leaf Mahogany


The Mountain Mahogany (Cerocarpus montanus) or better known as the Alder leaf Mahogangy is a native to the western United States and the northernmost parts in Mexico. It’s a cold hardy, drought resistant perennial evergreen that’s actually in the rose family. In its native habitat it grows in rocky soils with low nutrients and harsh weather conditions. In the nursery it grows in the shade, neglected and forgotten in probably less than ideal soil.


The reason it looks so tall and leggy is because it was in the shade.

IMG_2442Here is that less than ideal soil I was talking about, luckily for us this mahogany species is a really tough plant.


Because they have been in the pots for so long, and because they are so tough, I am going to go ahead and assume that they are root-bound. So I’m going to prune it first so it will be easier to maneuver when I get the dirt off the roots.


This tree grows its leaves in an alternate fashion.

So, lets see how the roots look now. I know there is a ton of controversy over how, or even if to cut off roots after a severe crown reduction, but let me tell you why I like to do it. The first reason, is that this Cerocarpus montanus has, like I said earlier, grown in a nursery pot for at least five years. When most long living shrubs/plants have been in nursery pots for a long time they are prone to growing something called a girdling root. A girdling root can grow in one of many ways, but the most common cause in most cases is spending too much time in a nursery pot without a proper re-pot. Girdling roots form when a root encircles another root or the stem (trunk) in witch case it is called a stem girdling root. This tree has both types, and they need to be removed before they get too big.


Above is the stem girdling root, below is the… root girdling root?


The girdling root is not particularly dangerous depending on how we approach it, but in the art of Bonsai it is distasteful, and can resemble a poorly planted tree that was neglected. In some cases though, the roots are left in tact because it introduces character to the tree. Sometimes trees can produce stem girdling roots in the wild due to growing next to rocks or less then ideal soil conditions.


So for this little fellow I am going to pull the roots out radially from the trunk, because this is the ideal structure for the plant to grow out the healthiest. First I have to take those roots out of the soil though and here is where I’m distraught because I’ve been debating for some time on the proper soil to make in my environment.


In the high desert of the Sierra Nevadas we get some pretty wonky weather. By that I mean we have stupid hot summers and frigid winters with rare and intermittent rainfall. We keep it comfortable with about 30% humidity most mid days. So I want to figure out a way to keep the soil porous enough for proper oxygen and humidity levels without having to water it ten times a day in the summer or mulch and bury it in the winter. Recently I’ve noticed the trees have responded the most positively to a low organic mix that was almost entirely coarse D.G. (decomposed granite) and lava rock, however, I am afraid that the winter will be too much for them in the shallow pots and new soil. So, on that note, this will probably be my last post concerning outdoor plants this year. I want to make sure they have plenty of time to acclimate to the new soil conditions before the winter comes, and winter is coming.


I am a bit concerned by the discoloration on the inside of the heartwood, could this be some sort of dangerous pathogen? I tried to wash it off because a part of me thought it was dirt, sadly, it is something else that I cannot identify.


Here is the finished project about a month later. You can still see the dark spot in the heartwood and it has gotten bigger sadly. Hopefully CODIT does its job, amarite? Above is the one that was covered in this post, below is a second one I did using identical steps except for that I planted the one on top in screened D.G. I think that will help it retain more moisture and heat in the winter, but as I suspected the second one I planted has been growing much healthier because I used coarse D.G. and there is a lot more airflow, heat and moisture. (Because I water it so often)


The two of them are still happy and healthy, though, and that’s exactly how I like it!



Author: garesgarden

ISA Certified Arborist, Amateur Botanist, and future Agricultural Engineer.

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