When To Re Pot Bonsai
This is a question i often see asked a lot among bonsai beginners but it is not a question that has a very straight forward answer, most of the times if you ask a bonsai professional when you should repot your treat the answer you get will be " Depends". This will then be followed by a list of questions that need to be answered before a correct answer can be given. But what we can do is give you some tips to be able to work out when your trees should be repotted so you can make that decision confidently yourself.
Identifying the differences between slip potting, potting into refinement and repotting
Often the term repotting is used as a blanket term for any potting technique used in bonsai, the problem with this is they all serve different purpose, have different timing and different techniques, so if you simply ask someone how to repot your tree or when you should repot your tree the answer can be very difficult without knowing exactly what type of potting you are planning to do.
We have a lesson on this in our Online Bonsai Beginners Course. We also have a full re potting course coming which will be linked at the bottom of this article once its available.
Timing For Different Species
Timing can change year to year depending on the weather, trees are triggered by natural events such as day light length and intensity and warmth.
With most conifers and evergreens a good rule of thumb is wait till the over night temperatures begin to warm back up but the day time temperatures still aren't extremely warm yet. The theory is here that roots need warmth to grow and usually grow during the night, so if you do your root pruning too early your roots may not grow back before they get infected ( the wound was open too long ). if the conditions are right the roots should repair their tips within 14 days reducing the risk of infections. we also want the day time temperatures to be warm but not hot. The theory is here that if the temperature is too hot and you have a weakened root system by pruning it then the tree wont be able to replace the water its losing through transpiration quick enough and could die.
With our Deciduous trees we want to wait till our buds swell and begin to break but not fully open yet. This leaves you a small window of time for Deciduous trees. The theory is here is similar to what we said above, once the tree begins to wake up from dormancy you will see the buds begin to swell, once they break you know the tree is awake and able to repair its root system quickly minimising the chance of infections, if you allow the leaves to open then its too late as deciduous tree are high water mobility trees and lose water fast via transpiration of their fine leaves, with a weak root system the tree can die fast in this situation. Making sure the trees roots repair before the leaves fully open is critical and is something you will just need to keep an eye on as there is no set timing for this.
Topical trees prefer to be re potted just before summer in the late spring, some people even repot through summer. This just depends on how extreme your summer temperatures are. For me in my environment we get pretty hot summers so i like to do mine late spring when the heat isn't so extreme but its high enough over night that the topicals function well.
Tools For Re Potting
There is a long list of items you will need to have handy for Re Potting, This includes
Root Pruning Shears - For Cutting Roots Clean For Fast Healing
Jin Pliers - For Tightening Your Anchor Wires
Root Hooks - To Remove Compacted Soil And Large Roots
Root Rakes - To Remove Surface Soil And Free Up Compaction
Re-Potting Sickles - To Remove Root Bound Trees From Pots
Potting Mesh - To Prevent soil From Falling Out Of The Pot And Pests Coming
In
Bonsai Potting Mat - To Help Prevent To Much Mess Being Made
Soil Scoops - To Move Soil
Soil Sieves - To Sort Particle Sizes And Remove Fine Materials
Bonsai Pots - When potting up into refinement for the first time you'll need a pot ready to go, otherwise you might need a pot if you are changing designs.
Bonsai Soils - After Repotting you'll need to freshen up your soil.
I hope this has helped give you a quick understanding of when to repot bonsai in the traditional sense. For a deeper understanding of all things repotting visit The Bonsai Dojo and Take Our Bonsai Beginners Course and Our Re Potting Master Class when its available.
