Root Pruning Potted Japanese Maples
I rarely remove a plant from a pot unless I'm transplanting but last year, I noticed that a few of our potted Japanese maples did not look as good as they have in the past. My first thought was root compaction. However, after sliding the tree out of the pot, I immediately saw something interesting.
The obvious culprit was the hole in the bottom of the pot. It was stopped up by roots.
Looking closer, I could also see an area that looked different. You can see a layer here that has a thinner, almost transparent quality -
First, I sliced off the bottom fourth of the root ball, right below the layer that looked thin -
Looking at it from the bottom, you can see that the roots are not that extensive. It certainly wasn't root bound. It shows why they are good candidates for containers. There is also a creeping wire vine (Muehlenbeckia axillaris) in the pot as well, and I suspected that it could have been causing problems. However, I didn't see any indication of that either.
I then repotted with fresh soil and did double-duty on the pot hole by placing both a light screen and a large, flat stone over it.
I wish I had photographed the next project, which was an umbrella pine in a pot, showing clear distress (the top tip of it had already turned brown). After I unpotted it, I discovered an entirely different situation. In the early days, to save money and not knowing better, I had used a variety of objects in the bottom of large pots to take up some of the space. In this case, I had used crushed plastic pots. What a disaster! Never, ever do that! This poor tree was suffering, I suspect, from too many air pockets in the bottom of the pot. Needless to say, I filled the entire pot this time with soil, again paying special attention to the drainage hole. This was a very large pot, so the soil was expensive, but I hope it survives. It will certainly be happier. I swear its green color looked healthier the next day.
As I heard someone say recently, "gardening is a never-ending education".
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