AusBonsai

After seeing Ian's post https://www.ausbonsai.com.au/forum/view ... =7&t=27157 and having a lot of Ash seedlings I thought I would have a crack at it.

I used a piece of compressed fiber cement instead of metal, easier for me to get and put two young seedlings through a 4 mm hole in the plate. They are now almost a year old and I am happy with the result so far, not sure how to proceed from here. Should I root prune the roots above the plate and return to the pot and leave the roots below as is, or root prune the top roots and reduce the root mass below the plate. I was thinking that if i keep the roots below the growth for the next season would be stronger but not sure if this would be detrimental to the nebari I am trying to develop.

Any thoughts or suggestions always welcome .

Leaving the roots below may add some extra to the tree but circulation will stop soon anyway. Leaving the roots will not cause any problem to the new nebari or trunks.
I would certainly prune the roots above the plate to slow the really strong ones and encourage the smaller ones. It will also make more root ramification on the stronger roots.
I can see that both trunks are a similar strength and size. Twins look much better when one is a bit bigger so I think you also need to slow one trunk a bit to encourage a difference in size.

shibui wrote: ↑July 7th, 2020, 6:22 pm I would certainly prune the roots above the plate to slow the really strong ones and encourage the smaller ones. It will also make more root ramification on the stronger roots.

Would reducing them to about 1 cm be appropriate for the stronger ones? As it is a young tree I was thinking of giving it one more growing season before trying to control the trunks or do you think earlier intervention would be better. If so what method would you employ to achieve the desired result?

There's no scale in any of the photos so it is a bit hard to recommend actual sizes but 1 cm for the stronger roots would probably be appropriate.

There is no hard rule about when to begin restricting growth to achieve a particular rate. Left alone it could develop exactly as desired but I would keep more than half an eye on this one and make sure the taller one stays taller and thicker. You can nip the top out of the other one at any time through the year to slow it if required.

After the recent period of extremely windy weather I noticed it was starting to look unhappy. I had reduced one of the two trunks( as per Ian's suggestion) a couple of months ago and it had been growing well. I decided to check the roots and discovered the root ball below the plate had separated this was expected and I believe accelerated by the recent strong winds.

This left a tidy flat root ball that I repotted into the same pot after removing the separated section. I am expecting it to recover it's vigor over summer as the existing roots continue to grow. I may reduce some of the foliage if it struggles.

Hi Peter,

Nice work with the roots. You might find that growth just stops around this time of year anyway. Some of mine are doing this already. If you want them to thicken you can just leave them to accumulate energy, however, you can also partially defoliate them by cutting each compound leaf back to the last pair of leaflets. This will force the tree to push out another flush of growth. I have some small ash I am trying to develop and they are due for their second or third defoliation for the season.

Terry, thanks for your thoughts I have been doing some partial defoliation on my Ash forest for MJL's forest comp. The Idea there was to get some light in and get varying sizes of trees. Not really sure what to do with the twin trunk yet, would defoliating it now reduce it's overall vigor?

Defoliation is primarily a refinement technique. If you remove all the solar panels, the tree will need to expend stored energy to push new growth. Unless you let the tree replace that energy, subsequent defoliation will result in weaker and weaker new growth as the stored energy is used.

If you want to thicken your trunks, just leave them be. With adequate food and water, you should see reasonable thickening during autumn.