AusBonsai

DangerousDave wrote:Well.. the suspense is killing me.. but I’m off to bed..

Hey DangerousDave - I hope you slept well or did the suspense keep you awake ... ?
What could it be? Tune in for the next episode!

A number of people are positing their views.... I am going with the reflected heat theory.

For some reason I remember a TV show that scared the cr@p out of me and my friends were growing up .... maybe there’s something more sinister that reflected heat... cue the scary music!

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drying out quicker than you thought, looks like some iron chelate is needed also

Maybe the photo has given you a bum steer Fiona. I just put it against the red wall for the photo - gets rid of the confusing background so people can see details better. The first photo shows it in the usual position. Corrugated iron behind is a water tank which does not radiate any significant heat. It is also several metres away from these banksias. Pretty sure we can discount the reflected heat.

That brings us back to drying out as Boics and Max have suggested
In the past I have had similar issues with banksias, almost always in spring or early summer. Autopsies have revealed extremely matted fine roots with the inner parts bone dry which leads me to conclude that banksias (at least in pots) have fast growing fine roots. In my experience the roots fill the pot in a single year. This means that each spring there is very little room for water to penetrate into the pot so no matter how much or how well you water, the pots just keep getting drier until damage is done.
I think the early dieback this time resulted from inadequate watering (for the congested state of the roots) as the weather started to warm up but because there was no fresh new shoots there was no indication like there is now that this one has such long, sappy shoots.
I had meant to repot these before now but just haven't got around to it - there's a lesson there too. Looks like today is banksia repotting day at Shibui Bonsai. I'll take some photos so you can see the state of the roots.

Apart from passing on some info about banksias I was hoping this thread will help show how easy it is to jump to a conclusion using 'established' theory. I'm surprised that only Mike suggested P toxicity because that's usually the first thing blamed for any banksia problem but I assume that's because many of you are aware of my thoughts on banksias and P so hesitated to jump into that trap.

Hi Shibui (Neil) i air layered a B. ericifolia when i first joined Ausbonsai .The first year i gave it very little water, what young light green growth that grew was about 30mm. This was because of the belief. This year i have saturated the pot nearly every day. It has responded with roughly 100mm of tip growth and still going next step is to find out the best fert. After i find that out, i can finally do my trunk chop with no fear

I haven't had a lot of experience with B. ericifolia as bonsai but they should respond similar to the other banksias. All the species I've worked with respond very well to chopping. New shoots from all over the trunk, especially lower on the trunk.
I generally use powerfeed on the banksias because it is low enough in P that even those with proteoid roots are not usually affected. If it hasn't had much feed before I'd even start out with half strength and gradually increase the rate to recommended rates after 4 or 5 feeds.
note that not feeding is not an option. In early trials when I too was frightened of killing banksias with fertiliser most died from starvation.
They have all responded very well to root pruning any time during summer and roots can be reduced significantly. Root pruning will remove most of proteoid roots if present and you can start feeding without any problem soon after root pruning.

Some photos from today's repotting session I took the opportunity tto do an annual reduction while I was at it. Dead shoots removed. Vigorous shoots coming from the wrong places removed. Existing branches thinned a bit and shortened where possible. The roots As expected it is just a solid mass of roots. I could not compress the mass even a little so the entire pot is filled - no spaces for water. Following my usual repot procedure I sliced horizontally through the roots about halfway down.
I was not disappointed. Despite a good soaking last night and again this morning the centre is still dry. I'm even more convinced now that the dead shoots were caused by lack of water due to being badly root bound. Repotted with fresh mix - plenty of room for new roots and water.

This has been a very interesting thread. I am sure that others, like me, have learnt a lot from this and in the long term our trees will be improved.
PS - I like the pot.

"repotted with fresh mix" bottle of Boag?

Very useful thread to follow for sure! I've dug a marginata out of the front garden and cut it back hard to use as a way for me to move beyond my 'plant racism' of disliking the native species. SO so far away from this tree, just a big old stump at the moment, but good to see some things to be carefull of in future

Geeze Shuibu,
Last night you had me magnifying your pics & squinting all over for signs of spider mite... FYI - I couldn't find any.

Yes. I too have noticed the masses of fine roots over the years in both my b.serrata and integrifolia.
I treat the same, simply saw through half way horizontally and rake out the rest usually when tree is active.
There is almost always next to zero substantive roots in my pots, just fine ones only.

And on the flip side. If you have bad drainage and the roots are staying wet too long, you often get die back in random areas like this too. At least that’s what I’ve experienced, especially with marginata.

shibui wrote: I'm surprised that only Mike suggested P toxicity because that's usually the first thing blamed for any banksia problem but I assume that's because many of you are aware of my thoughts on banksias and P so hesitated to jump into that trap.

That's because I just assumed you knew how to water....

treeman wrote:

shibui wrote: I'm surprised that only Mike suggested P toxicity because that's usually the first thing blamed for any banksia problem but I assume that's because many of you are aware of my thoughts on banksias and P so hesitated to jump into that trap.

That's because I just assumed you knew how to water....

Bahahaha!


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