Repotting JBP in Autumn

[longd_au]

Hi

Recently, I killed (I think I did, they take a while to die) a JBP because I tried repotting it in early Autumn. I am in Melbourne.
Given I grow them in quite an open mix, all the soil fell off. This exposed some long roots that were circling the bottom of the pot so I cut them off.
I have done this before in Spring without any problem.

I should also add my pine is a young one. Probably 3-4 yrs old.

My questions are:
Is Autumn really a good time to repot JBP?
Did it die because it was bare rooted?

I know there probably isn't a single answer but what would be the most likely cause?

BTW, I repotted it coz I need the pot it was in.

[treeman]

If the soil fell off it either did not need repotting or the roots were gone. Either way, it's a dangerous operation likely to prove disastrous.. Generally there's no problem repotting in early autumn in Melbourne.

[longd_au]

Hi Mike

Thanks for your reply. The soil fell off because I am trying to thicken the pine and planted it in a large pot. There isn't enough roots to hold the soil together.
The JBP was in good health and I wasn't expecting it to die. This is the first time I repotted in Autumn. I am guessing the combination of bare rooting and cutting too much roots?

Not sure if it is comparable but I've pulled Radiata out of the ground in winter and in summer and have observed that the ones in winter almost always don't make it.
Would really like to hear what everyone thinks.

For now, I am avoiding Autumn repotting unless I know it won't bare root.

[treeman]

Hi Mike

Thanks for your reply. The soil fell off because I am trying to thicken the pine and planted it in a large pot. There isn't enough roots to hold the soil together.
The JBP was in good health and I wasn't expecting it to die. This is the first time I repotted in Autumn. I am guessing the combination of bare rooting and cutting too much roots?

Not sure if it is comparable but I've pulled Radiata out of the ground in winter and in summer and have observed that the ones in winter almost always don't make it.
Would really like to hear what everyone thinks.

For now, I am avoiding Autumn repotting unless I know it won't bare root.

The worst thing you can do is plant a young pine which has had a severe root pruning in a large pot and water it. It's a quick way of killing it. The correct procedure is to keep the tree in a small pot and transplant when it is full of roots and then only shave off the outer part of the root ball and go into the next size pot only. 50mm of room all around the roots is ample. Any more than that you will need to monitor the watering very carefully (impossible in a Melbourne winter) and there is always a risk that unused soil (without root activity) spoils. (gets invaded by decomposing organisms etc). New roots will seldom enter that - especially pine roots. The alternative is to plant in pure sand with maybe 10% organic. You will have less trouble with this mix in a big pot.

[dan.e]

Ryan niel/mirai bonsai have some great vids on the subject of repotting and water oxygen ratio some free ones one you tube but others you have to subscribe to Mirai

[shibui]

Although I have not root pruned trees in Autumn yet there is enough evidence from experienced growers that it is safe.
I have not found that bare rooting pines is the issue it was once supposed to be because I regularly bare root trees here as young seedlings and as field grown trees.
Your problem may have been more to do with some other problem with the tree, possibly related to the large pot as outlined by Treeman.