The fig tree last July
The rain held its breath and I decided to get the root pruning of the fig over with. Once I have an idea in my head it's hard to think of anything else.
How did I know I should prune the roots? First, a very, very compact feel to the soil in the pot. No loose soil. Second, when it is watered the water runs straight through, like a sieve. This necessitates multiple waterings to make sure the roots have time to absorb anything. Not a problem now, but it will be in summer. Third, moss. My pots always pack on the moss when the roots are compacted. I think it likes the firm structure and rapidly draining, frequent watering. Another obvious clue, and I was unable to see this before I pruned, if you can pull the plant from the pot and see its roots visibly wrapping round and round, it needs pruning.
The plant should be dormant, so late winter/early spring is a good time to root prune or else fall. Pick a day when the temperature is well above freezing.
To give you an idea of where a tree's roots will extend naturally in the earth, look at the spread of its branches. As far as the branches spread above ground, the roots will spread below. So a tree in a small pot is fighting its natural instinct. Intervention is required if the tree is to stay well fed and well watered.
Now, I have never taken a bonsai class. And I am sure that a bonsai master/mistress would be appalled by my methods, which are not delicate. All I can say is that they work, or have so far. I have green fingers, so whatever instinct that implies or describes, must help. I kind of think, wordlessly, What would I want if I was this plant?
Answer: SAW MY ROOTS OFF WITH A SHARP BLADE!
Perhaps some things are better left unexplained.
You need: a sharp saw with teeth, or very good bread knife. The saw is a better bet, but the knife will do if the roots are not big and the plant is small. The better the saw, the easier the job will be. I use Felcos.
If you cannot pull the rootball from the pot (and my fibreglass pot has a lip which prevents this, which is annoying), operate in the pot: pretend your roots are a cake in a deep dish, and cut around the edges of the dish, or pot, as far down as you can go. Small, fast sawing motions are better than big, slow ones. How much you remove depends on the size of the pot. I took off about one inch.
Once you have cut all the way around, it is easiest to lay the pot on its side, and pull the newly revealed root ball out by holding the trunk and wiggling back and forth. You may need a friend to hold the pot while you pull.
My new root ball came out pretty easily, the flap of cuts roots still attached at the bottom.
The lower part still needed a lot of pruning as the pot tapers narrowly towards the bottom and my saw had missed them. I trimmed individual roots with my pruners. Felcos, of course.
I also shaved off an inch from the very bottom. Then I teased loose as many roots as I could near the edges, to show them the way into their nice, new soil. New root hairs will absorb nutrients.
I poured some good potting back into the pot and lifted my lighter fig tree in with a clearance of an inch all around.
Added some more soil around the edges, and watered.
Now we must wait and see.