Soil Mixtures- sizes


(Bill Daniels) #1

I have two junipers… 1 in a 5 gal plastic pot from nursery & a Hollywood juniper placed into a 3 1/2 gal bonsai pot. Both need repotting this season. I will be using large Boom mix. for the two plants.

After reading, re-reading material and researching the subject a question came to mind. Yes you want air pockets within the soil structure BUT would using a half and half mixture of Boom soil such as: 1/2 medium and 1/2 small mix be ok? Or 1/2 Large and 1/2 medium for larger plants be ok?

It would mean smaller air pockets…
It also means there more surface for roots to get nutrients from.

— What it means also the air pockets to get clogged easier because the air pockets are tighter…

Would this be beneficial for the Bonsai?


(Jonas Dupuich) #2

A very common approach is to use larger mix in the bottom portion of the pot and smaller mix near the surface.

The lowest part of the pot tends to stay wetter and the surface of the soil tends to dry faster. Using larger particles below and small particles above can provide more air below and more moisture above.

Container shape is another consideration. If the pot is shallow, I’ll tend to use small mix. If it’s larger and deeper, I’ll use medium-sized mix below and add a layer of small on top. I’ll typically use a drainage layer of pumice in both cases.


(Frank Corrigan) #3

One other consideration may be to adjust the particle size according to the stage of the tree’s development. Since smaller particles encourage finer, more ramified feeder roots, and larger particles encourage heavier, more structural roots. Smaller aggregate size near the top produces finer roots near the surface as we compact the root ball to move Bonsai into progressively smaller containers.