When to do Trident Maple root over rock, and pruning?

[sheepdawg]

Sorry, if this is in the wrong place.
I want to do a root over rock planting with trident maples. I'm basically going to follow Shibui's guide. I have four in total, so hopefully I'll have a fit (3 that were collected together and a 4th that I got for $1).

First question: when would be the best time to bare-root them and stick them on the rock? To me, bare-rooting is usually done in mid-winter, but would this kind of thing best be done when the buds are extending? And what if I want to make some "major" cuts on the branches? (I say "major" because they're <1 year old, but some of their "branches" are over 0.5m long, so I might need to reduce these).

Second question: I'm considering using that group of 3 all together (most likely the smaller 2 though) to get a greater root coverage, help with trunk thickening (fusing them), and as an "insurance" policy in case one dies. Would this work?

Here's the planned rock:

[kcpoole]

When the tree is dormant is the safest time to work on roots of deciduaous trees,
so yes in winter, or just before bud swell.

Ken

[bodhidharma]

At what time do they go dormant in toowoomba I would have thought late Winter, August/September, where you are.

[sheepdawg]

At what time do they go dormant in toowoomba I would have thought late Winter, August/September, where you are.

Not sure to be honest. Collected these guys from bin thingy when all the seedlings were being weeded out last spring in a park (bought the other a few days ago). So this is my first autumn with them and I cannot wait to start seeing them turn

[Craigg]

They should be dormant in July/August inToowoomba. I usually do all the heavy root work starting from July with no problems over the last 3 or 4 years. Now that I have moved to a colder spot I am intending to start in mid June and see what happens.

[shibui]

Tridents are very forgiving species. I put my root over rock plantings together any time from mid winter through to first leaves showing. You can bare root these any time when they are dormant.
Even if your trees do not lose leaves in winter they are still very close to dormant in winter so this can be done. My Chinese quinces do not lose leaves in the grow beds. Eventually I got sick of waiting and bare rooted and root pruned with no problems. Pines are not deciduous at all but can still be bare rooted and root pruned in winter without any ill effects so don't worry about your trident maples.
Also when putting them on the rock you will probably not cut off much root so you're not really root pruning. They will probably not even notice you have done it and I doubt that it would matter much what time of year it was done.

Grouping 3 together on the rock should work but there are a few provisos:
Roots must grow on all sides of the rock. If you only have roots on one or 2 sides of the rock as they thicken the pressure will push the tree away from the rock and leave undesirable spaces. I can foresee if you place 3 tridents at the same place and run roots from each down a different face of the rock that the 3 trees will just get pushed away from each other and never get the chance to unite. Tying the base of the trunks together would hold them in place but they will thicken so quickly that the tie will cut into the base and damage the trunks, probably produce an area of inverse taper there so be careful.

Trident trunks thicken pretty quickly anyway. What about getting hold of 2 more rocks and make 3 ROR tridents. Then you have 2 spares for insurance and, if one does not look really great you can pick out the best ones at the end. Your seedlings may or may not have suitable roots to drape over the rock. I normally start with about 100 seedlings to find the best ones to fit around 20 rocks. Not all seedlings have the required root arrangement for good ROR (plenty of longish roots coming from one place below the trunk) or the right root/ trunk shape to fit on any given rock so don't be too disappointed if the first attempt doesn't turn out quite as well as you hoped. Even after years of developing this technique I still have some that don't work properly.

Good luck with the project.

[sheepdawg]

Thanks Shibui!

It seems so obvious now, I will get some more rocks and try them all (except one, I'll going to plant that in the ground today). Now, all I have to do is find some more rocks. I also used that rock for a ficus planting because I found a F. rubiginosa with deeply red leaf stems