Adding a base layer to your pot while repotting works wonders for your bonsai tree. Not only does it prevent compaction, but it also prevents root rot by ensuring quality drainage. So now that we know that a base layer is essential to a healthy bonsai tree, what should we look for when choosing one?
Material: You’ll want to go with a large aggregate when choosing your base layer. Commonly used materials include pumice and lava rock. Our favorite is lava rock due to its porous nature and varying sizes. On our best trees, we use the large size of lava rock, roughly about 1/4″ – 1/2″. You’ll want to avoid anything that will break down too quickly when it is soaked in water such as akadama.
Durability: Durability is very important since you don’t want to repot your bonsai tree more than you need to. If you use a material that breaks down, then it will accelerate the compaction at the bottom of your pot. Since you want to avoid this, it’s best to choose something that won’t break down. This counts out akadama as well as any type of organic soil. Pumice can work but it will start to break down over time. If you don’t mind repotting, then pumice might work for you. Our choice is still lava rock. It’s extremely strong and will not break down easily.
Weight: This element is often overlooked. You’ll want to be able to carry your tree without injuring yourself. Sometimes people will go with granite for their base layer. While granite is extremely durable, it is also extremely heavy. Pumice is an extremely light material making it an adequate choice for a base layer. Lava rock is slightly heavier but is also a good alternative.