Heat Stress Mini?

[Huw.S]

Hi all,

I have a shohin banksia serrata in training which was going really well. Had some great small foliage and was shooting everywhere. However, recently we had a very hot day (about 40 degrees celsius) and since then it has looked very unwell. The leaves are all brown and wilted and all of the shoots are very weak. The soil did not dry out, i watered in the morning and afternoon because i knew it was going to be hot, as well as that, the tree wasnt in the full sun on this day, i kept it in partial shade.
Maybe there is another reason for its deterioration. In any case, if anyone has some advice on what to do for it now would be great, other than keeping it shaded and watered.

Cheers Huw

[dennismc]

Hi Huw

A common problem with Banksias They thrive for a while then start to deteriorate and die. Even watering twice a day is ineffective if the soil dries out between watering, likely to happen in hot summer weather.

My own early (and similar) experiences led me to do some research.

To cut a long story short, I discovered that in order to keep them thriving they MUST NOT dry out in the hot weather. For many years I have kept my Banksias standing with at least 50% their roots in in water from 1 December to at least the end of March, or until the weather becomes milder. They thrive in this environment and give considerably increased rates of trunk thickening.

Recently by accident I put this theory to work as I have been traveling a bit and neglected to place my B praemorsa in a water tray. When I finally settled back home I could not understand why the tree had only put on a minimum of growth and was looking less than ideal. On realizing what happened I immediately placed it in a water tray and two weeks later it has completely recovered and is putting out a tremendous amount of new growth!

regards
Dennis Mc

[Pearcy001]

Hi Huw,

Over the past 12 I've ran into many problems with my BS. I too as above use a water tray - mine is just an old bucket lid leaving it about 1.5cm deep water. I pretty much water when the tray completely runs out of water or maybe a little while later keeping the soil moist.

Did you put your BS through any other stress in the time leading up to it's deterioration? ie. When did you last repot or prune etc? How do you fert your BS?

A picture speaks a thousand words Good luck with the tree.

Cheers,
Pearcy.

Sent from my SM-G920I using Tapatalk

[Huw.S]

Hi Dennis and Pearcy, thanks for the advice! Ill keep it in water now until the weather has definitely subdued. And no major stressors recently, the minor trunk chop was at least a few weeks ago. Guess all i can do now is wait and hope the little guy pulls through.

I have attached a photo of it anyway, hoping it doesnt die on me.

Huw

[shibui]

It does not look too root bound. That was one of my early discoveries - because I was afraid to re-pot natives I left them in the pot for several years. Banksias produce huge amount of very fine roots so the pot quickly fills with roots then it is difficult for water to penetrate and the trees deteriorate and die. I have learnt to repot banksias often - annually when young and vigorous.
As outlined by the others banksias do seem very sensitive to drying out. One dry day can be enough to kill them but they don't show the signs for a few days so it can be hard to pinpoint when it happened. Unlike other species that can recover from being dry banksias don't seem to come back. I hope yours has not had it too bad and will recover.

Fertiliser: Banksias can be sensitive to P. The can get used to any fertiliser but if they've been hungry and get a dose of high P fert it can kill them. BUT.... because I was worried about hurting my banksias with P I was reluctant to feed them anything fearing it may harm them. Many more of my banksias have died from starvation than have died from excess P.

Phytopthera: Banksias seem to be particularly sensitive to these introduced root rot fungi. We see whole hillsides in national parks dying from Phytopthera and it will also kill banksias in pots. Fortunately our eastern banksias are a little more tolerant than the western species. Preventative fungicide may be worthwile when growing banksias?????

[Rory]

I actually lost more banksia when I started out, from not having enough sun, and the soil staying too wet too long than anything else.

Looking at your banksia now , it certainly wont have the problem of drying out, as there will be no real water transportation now. Ironically, now with no foliage, just make sure you don't keep the soil damp, as the roots will start to rot.