Advice on separating from trunk - cotoneaster

[Action Jackson]

Hi All

This cotoneaster needs a repot. The reason it looks wet here is that I wasn't getting penetration to the roots and dunked it for a drink.
I'd like to separate the trunk and make two trees out of it. If you look closely (sorry about the photo angle - will get another one tonight) the trunk goes into the soil and both areas have roots

How do I go about cutting this join? I'm guessing it is not as simple as splitting it down the middle?



Thanks

[shibui]

Yes it is as simple as splitting it down the middle AJ.

Neither of these trees will miss a few roots that you cut when splitting this.
To end up with better nebari (surface roots) it is desirable to try not to cut those surface roots right off but it is often not possible in which case just cut right through.

Looks like the tree has not started growing yet so you can do plenty of root reduction. I would start by cutting or sawing horizontally through the root ball about 5 cm down - there are plenty of surface roots that will maintain the tree afterward. Then cut around the edges of the shallower disc you have left - probably cut off around 2cm (depends on the size of the pot). After that rake out more soil with a bent rod, bonsai rake or stick. Keep trimming the exposed roots until you only have a circle around 2-3 trunk diameters across and maybe 1 trunk diameter deep. After that you should be able to cut whatever is holding the trunks together a bit easier and separate the 2 trunks. I suspect you may find one or more really thick roots/trunks under there which might make it a bit more difficult. If it gets too hard or if you are too worried feel free to leave a few more roots but this tree will cope with massive root reduction. I would probably also prune a fair bit off the top of the larger one and possibly a little off the small trunk to reduce water demand on the reduced roots but there is evidence that that's not crucial.
Pot up the remains, water well and put them back where they are used to being unless that place gets a lot of strong sun. Keep slightly on the damp side until new shoots appear then treat as normal. Remember that sun or at least good light is important for developing new roots so best not to put freshly repotted trees into very shady place.

[Action Jackson]

Hi shibui I will follow your guidance and put up a before and after photo tomorrow.

Thank you so much for your knowledge and willingness to help new comers. The detailed responses are really a treasure to read, I look forward to such and love that there are enthusiasts such as yourself always here to help

[Action Jackson]

Here is my attempt, the split was much easier than i had thought.



Larger tree



Small tree


Trimmed a bit of larger tree but left the high top in the hopes of air-layering the left bunch

[shibui]

Well done with the separation and the root pruning
I think this is C. microphylla. I have some and they make great small bonsai because of the tiny leaves but they do have a very straight and stiff growth habit so you will need to prune a lot or wire young shoots to get enough bends and movement into the trunks.
It should layer well and strikes really easily as cuttings.

[Action Jackson]

Thank you shibui - any advice on fertilising and getting the tree to produce berries?

[shibui]

Mine have flowered and produced berries without any extra attention at all. In fact, they produce a better crop than the C. horizontalis which is more common.
Maybe neglect is the key? but I usually fertilise flowering plants well with any fert during spring but switch to something tailored for flowering species around mid summer and continue with that until later in autumn. Packets labelled 'flowers and fruit', 'tomato', citrus, 'camellia and azalea', etc are all slightly higher in K and should help your flowering plants to bloom and set fruit a bit better than a high N fert. I believe the key is to start before autumn which is when the embryonic flower buds are starting to form.