Radiata Pines; Something peculiar happening

[NBPCA]

Hi all,

I have heard over the last year that down in Melbourne; where for historical reasons there are lots of Old Radiata pine bonsai: that there have been some deaths of older trees or serious damage after removal of old limbs for restyling etc.

One experienced grower is now wary of cutting off large portions in case the tree fails and unfortunately another grower is possibly losing a few radiata . Similar treatment to J Black or Red pine has not had the same effect.

Whats going on here that is particular to Radiatas and old Radiatas especially?

Has anyone any experience or light to shed on this phenomena.

Many years ago Leo Coolwyn showed me grafted Radiata pine that were grafted onto a different understock(possibly J Black pine) because he said " the Radiata has a weak root system". Radiata pine seem to live only about 150 to 200 years in the field in Australia which is not old for Pines in general.

Those who have old Radiata: when do you repot? Trim? Hard Trim etc.

I want to find out what are the possible causes and how to avoid for everyone.

Grant

[Brian]

Well Grant, this happens to be right up my alley . I repot my old radiata pines only every three years or so. Now is the optimal time for repotting. With regards to removing large branches, I usually leave a stub about 50 mm long from the main trunk. Then 6 months later trim flush with the trunk. I have drastically trunk chopped very old specimens without any issues. If I can be of any further assistance please ask.

Brian.

[NBPCA]

Well Grant, this happens to be right up my alley . I repot my old radiata pines only every three years or so. Now is the optimal time for repotting. With regards to removing large branches, I usually leave a stub about 50 mm long from the main trunk. Then 6 months later trim flush with the trunk. I have drastically trunk chopped very old specimens without any issues. If I can be of any further assistance please ask.

Brian.

Hi Brian, most radiata would be in full candle elongation at the moment; how long ago did you repot or have you done something special?

One I have here in Canberra is certainly in strong growth at the moment and hasn't been repotted for quite a while by the look of it..

Treat em like a J Black pine seems to be the concesus. What do you think?

How much % of foliage have you ever removed at one time?
Grant

[Brian]

Yes the candles are elongated now, so as long as the tree is growing, I would trim the roots now. I am not repotting this year, just make a few holes in the soil for fertilizer.
I use blood and bone, osmocote and all the usual liquid fertilizers but avoid dynamic lifter.
I always do a substantial needle pull removing up to 60 % of the old needles. I find around late November works for me. I just check each week by pulling a few needles and see if they tear out cleanly leaving the inner brown sheath intact. If the inner sheath pulls off then its too early to remove needles.

[Chris H]

Thats interesting. I tend to repot before the needles open.
I have always thought it too late to repot once the needles really elongate and start to open.

Brian am I correct in taking from what you say that you wait until later when the tree is really running before you repot?

[Brian]

Yes, thats correct. I wait until it jumps away with spring growth then root prune. I have done this for over 20 years without loss of a tree. This is my personal experience and what works for me. I know others may disagree.

[Chris H]

Good to know.
I have left my JBP till last when I repot - but have often resisted going ahead with those that are already popped.

[NBPCA]

Yes, thats correct. I wait until it jumps away with spring growth then root prune. I have done this for over 20 years without loss of a tree. This is my personal experience and what works for me. I know others may disagree.

Interesting! It does sort of fit with my theory that the radiata should be kept reasonably full of foliage; more so than others; to exercise the potential weak root system.

I have decandled and repotted black pine in late spring but not left on elongating candles.

Grant

[Brian]

A bit of thread drift here, but the late Mr Ian Edwards botanist and horticulturalist taught me to repot atlantic cedars the same way, after it starts making new growth.

[Grant Bowie]

A bit of thread drift here, but the late Mr Ian Edwards botanist and horticulturalist taught me to repot atlantic cedars the same way, after it starts making new growth.

Also interesting; maybe a Melbourne thing?

Grant

[Brian]

Grant, I should clarify that I pinch back the candles a week before repotting. I find that the candles can droop if left in full when root pruning..

[daiviet_nguyen]

Good evening,

I have read else where that not all radiata pines are the exactly the same in Australia, some has been genetically modified for timber plantation, hence there might be an issue with longevity?

-- I cannot remember where exactly.

It is the only pine where I have successfully grown from cuttings.

Regards.

[Dario]

Mine are not old trees but two weeks ago I repotted my radiatas removing all of the old soil. They were collected a couple of years back.
I repotted when the needles had opened and the candles were starting to move.
Two days ago I noticed that some of the new growth had started drooping.
Thanks for the tip Brian, next time I will pinch back the new candles a week before repotting
Brian, should I pinch the drooping candles now or just leave them?
I have been misting the trees but it doesn't seem to have any affect on the drooping candles.
Brian, do the drooping candles die or come good in time?
Cheers, Dario.

[Edward Scissorhand]

Grant, I have a middle aged/old radiata (1960s). I live in Sydney and I repot mine in late winter to early spring. I do pruning all year round but Ive never ever hard pruned this one. I prune this one very lightly and conservatively.The biggest problem I have in Sydney for this pine is needle cast. Generally in spring, where rain on sunny days presents big problems for me. Theyre good conditions for the problem to spread, so now I carry the the tree under cover when it rains and pick off every single needle thats infected before it spreads from things such as insects and wind etc. You can see the black tiny spores when the needles reach a certain colour. It isnt Dothistroma that I have problems with, its cyclaneusma. I reckon the worst one to get. The old radiatas are not as resistant to these problems as the new ones. The new radiatas have been selected from trees that seem genetically resistant through selective growing from plantations that were devestated by this sort of problems. I never ever water any part of the needles, only the soil. The new radiatas dont seem to be effected or only effects them slightly from watering on its needles and I have alot of the new radiatas that Ive tested on.

Have you got any pics of the dying trees? How much did they prune off at one go? Do they seal the wounds? Can you give us a description of whats happening to the trees after cutting and during the dying phase?

[John Henry]

Hi All, i have several very old Radiata pines and would be interested to know what other growers potting mix consists of and have they had any adverse effects.Does any one use Maidenwell diatomite or Mt Sivia in their mix on OLD Radiats.
Thanks John