Banksia root rot after care

[MattM]

Hello all,
I've never had a banksia survive root rot but I think I caught this one early. I have removed all damaged roots and put in a small pot. I repotted in my new mix I have been using of 33% pumice, 33% scoria, 33% mini pine nuggets.

Should I leave the plant in the sun or shade?

Should I water it or leave it?

Do I mist the leaves?

Should I peroxide spray the damaged leaves?

I am in humid wet western Sydney. Any advice would be appreciated.
Thanks,
Matt

[Rory]

Hi Matt...

Banksia are definitely prone to root rot. I have had quite a few Banksia develop root-rot that I've had to deal with.
DO NOT cut off any leaves. You will need as many leaves remaining to try and promote new root growth now and to pull water out of the new mix.
The best solution to prevent further rot is to remove all the affected rotten areas and cut back into healthy growth. Remove ALL the old soil and use a fresh mix. I then spray all the affected area of the entire roots with the standard recommended solution of RID-ROT just to be sure.
The next step is to make sure the roots are not over-potted. The pot should only just be big enough to fit the roots without much room. You do not want it sitting in a wet mix if its not pulling up much water, especially as we are approaching winter soon.
The main problem you will have now is that after all the removal of the rotted roots, the tree is not going to be pulling much water out of the mix now as it may sit dormant now till Spring, or it will try and send out new roots, depending on how healthy it is.
In future you need to ONLY water the mix again when it gets quite dry. And I mean you need to be anal about this. If its forecast for rain, bring it undercover to avoid rain.
You want the tree in as much sun as you can give it. (but if you've had it in strong shade, then putting into full sun might burn the leaves.) You can build up the sun exposure each day, but from my experience if the roots have had root rot, you need to have it in as much sun as you can give it, ..... preferably forever.
Your mix should be very free draining. A mix with larger particles and/or even washed river sand can help with drainage.
Low sun and/or slow draining mixes are really bad for Banksia.

Good luck, and make sure you keep a close eye on the foliage now for many months. You don't want pests eating the leaves. If it gets defoliated, it can be a death sentence when it has been badly affected by root rot. Personally I like to over-protect my bonsai during this sick period. I would occasionally spray with a light spray of pyrethrum on the foliage, just to protect it from leaf munchers. But don't spray on a hot day.

What do you mean by peroxide spray the damaged leaves?
If the root rot is bad, the leaves may have turned yellowish or be wilting. Thats not a good sign. Are you sure you got rid of all the rot from the roots.... it hasn't got into the trunk has it?

[MattM]

Thanks for the information Rory, it's greatly appreciated.
I only repotted it today, I noticed some of the leaves were wilted. I'll see how it goes
Thanks once again