Repotting banksia

[shibui]

This is one of the banksia integrifiolias I've been developing for a few years.
Started with a tall trunk, was trunk chopped and responded with plenty of new shoots. Those have been chopped a couple of times since but it is time for another trim.
After trimming I decided it could probably do with a repot as well because I've found that banksias grow lots of fine roots and get pot bound quite quick. Then it becomes really difficult to water properly and death is often a consequence. Note the self sown maples in the pot indicating that it has been a couple of years since last repot for this banksia

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Proteoid roots are a feature of bankias and some other plants from proteacea family. Proteoid roots are super efficient at absorbing Phosphorus and help these trees survive in nutrient poor soils but when we offer fertiliser the proteoid roots are not selective and overdose of P can kill the tree. Proteoid roots only develop when there's a shortage of nutrient in the soil. They will slowly shrink and eventually disappear when you gradually introduce low P fertiliser to the mix or can be trimmed off while root pruning.

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Always feed proteacea family with low P fert unless you are certain there's no proteoid roots.

I've found that banksia roots are packed real tight and hard to cut with root pruning scissors. Fortunately they are also quite brittle so easy to break off chunks instead of cutting.
After root pruning

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There were several self sown maples growing in the pot so while I was repotting I saved those and potted up separately. Summer is not known as a great time to repot maples but experience has shown most will survive transplant.

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[Rory]

That is a small Banksia integrifolia. Well done for keeping it compact. I have tried a few Banksia integrifolias as a similar size, but eventually I cave in and grow them larger. (not sure if its my laziness or a preference for larger). I have not attempted to reduce integrifolia leaves for something this size. I'd be interested to see this in leaf, and what it looks like when its at the stage of leaf size that you're happy with. Hope you don't sell it and post yearly updates.

How many years has that been since you repotted that Neil?

[Watto]

Great post, very interesting and informative.

[shibui]

How many years has that been since you repotted that Neil?

I have far too many trees to record details of each but from the size of the JM seedlings I'd guess 2-3 years since last repot.

[MattM]

Hello Neil,
I'm confused. You have root pruned this banksia and you have defoliated it???
I thought you have to leave lots of foliage on banksias when you root prune them. Also thought you couldn't prune the foliage and root prune banksias at once, or they would die.
Banksia integrifolia is my favourite bonsai species by far. I have been working on them over the last 8 years, have about 15 at the moment. They are a difficult native plant to bonsai I think, but I keep trying. I have lost some to root rot, and some to the root ball being to compact and dieing due to lack of water. I keep replacing the dead ones with new stock.
Do you leaf prune and root prune this way all the time with integrifolio? And what mix do you use?
Thanks,
Matt

[shibui]

We will be able to watch this one to see how it recovers.
I have done this chop and transplant a number of times with banksias from the garden and from the grow beds. Some I pruned a few weeks before transplant so dug and potted with new shoots just opening. Others I pruned and dug right away. Survival from both was similar.
I don't think I have root pruned but not pruned the tops before. Something for me to to try at some stage and see what results that gives.

Like you, I have lost many from the pots being badly root bound and not able to absorb water, especially young, fast growing banksias. Took a few years to realise what was happening but survival is much better now that I repot regularly.

Mix is my standard potting mix - 70% superfine pine bark + 30% propagating sand with small amounts of zeolite, dolomite, trace elements and fertiliser as required to balance the mix to potting mix standards.

[Rory]

I'm confused. You have root pruned this banksia and you have defoliated it???
I thought you have to leave lots of foliage on banksias when you root prune them. Also thought you couldn't prune the foliage and root prune banksias at once, or they would die.

There are many ways to skin a Banksia. Everyone has different methods.
Notice that Neil left a lot of root on this Banksia. In this strong growing season, it will be fine.

When I started with Banksia, I did the same as Neil. The main times I ran into problems with Banksia repotting was when I was stupid and put the tree back into a pot that was far too large for the newly reduced root ball....thus it was overpotted, and root rot would slowly develop.
Personally, I leave most of the foliage on after a root removal, but that doesn't mean its the right method for someone else. It just means whatever works for some, is what they trust and keep doing.

In particular, this cute little tree of Neils is just that,... a little tree. He presumably wont want a huge flush of growth to rocket out. Once a banksia thickens - and they will thicken fast with all the foliage left on to grow quicker - you can't go back. His goal is probably to develop a lot of ramification now and a nice canopy for this little guy. The best way for that is complete defoliation. For integrifolia, this will now burst everywhere once it recovers. It is also the best way to get back budding on Integrifolia. As an example, with my larger material and from my experience, it is almost impossible to get back-budding low on the trunk of aged integrifolia. So you have to really encourage it while its developing, and the best way is a complete defoliation and major cutting back.

[shibui]

Budding was slow but that banksia now has lots of new shoots.

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I can also confirm that all the maples survived the summer transplant too.

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[Grant Bowie]

The banksia looks great Neil, Love it. I’ve been meaning to have a go but never got around to it.

You have done amazing work with great timing, considering how weird the weather has been the last three years. But finally the banksias are going” Wow, Great, hot weather finally”

Grant

[Grant Bowie]

Interesting about the younger plants dieing, yes they need to grow and get a good head of foliage going, I move to next size pot pretty quickly so they don’t stagnate.

Older established bonsai I may trim weeks or more before repotting, and not touch the foliage at the point of repotting

Grant