I have come across a really great tree that has excellent natural movement. Its a Birch and I am in the UK. The tree is about 4ft high and has been growing around some branches that have fallen and a holly bush so the trunk goes through 2 almost 90 degree bends.
I have permission to recover it if I want to, however I have some questions. The only reason I have found the tree is the path has been widened in the area, I assume that the best time to collect the tree would be Spring next year? However if I wait I am concerned the next time the path is maintained it is going to get destroyed. So what chance would it have if I collect it shortly?
Also what size of root ball is it likely to have?
To give it the best chance of survival do I pot it in my garden or a large 60 litre pot?
Then just to add some more questions… what would your plan be for the next 5 years to turn it into a bonsai? When would you give its first styling and when would you put it in a bonsai pot?
If you can shelter it for the winter, you can also collect it in the late summer. It is potentially a bit more complicated as it will need to rebuild reserves between the collection time and the leaf fall.
My experience with collecting birch is that while they’re tough and will likely survive, they are also prone to trunk dieback. It’s not uncommon for them to give up no that nice trunk you had your eye on and decide to sucker out from the base instead. So it’s more the odds of that happening you’ll be effecting by not collecting in early spring.
My two pence ref planting collected trees in the ground vs pots: I’d opt for pots or wood box. It brings a lot of control benefits which positively impact collected trees. Portability is a main one, and within that being able to control the amount of moisture in the soil (it’s pretty darn rainy in UK), move between full or partial shade and to easily bag & sweat it etc. If you wanted to, planting it in the ground after a couple of years when it’s recovered and grown back roots would be a better approach.
I agree about the dieback. I collected a 3 trunk clump Birch this year and two of the trunks have died back leaving only one which is doing well.
In terms of the rootball, thickness of the trunk and age are probably more relevant than height. Generally I collect about a foot either side of the trunk and then can reduce it whist potting it up. i also tend to go for later winter as the buds are swelling to collect because that is what I have experience with.
Hard to tell until you start digging. It depends on factors such as the type of soil it’s growing in. In practice, it rarely has a nice little compact rootball of a particular size and most the time the roots have gone a lot deeper and spread out a lot further than you’d be willing to dig. It’s more a case of what you can get away with taking for it to survive.
As @Twisted said, it’s height is also less relevant. For example, it could have been taller than 4ft at one time and snapped in a storm some years ago.
I would wait until spring. Maybe you can put some logger’s tape on it or something to ward of anyone who might not recognize its value and take it down during regular maintenance. In my experience collecting in the fall produces a lot less success than in the spring. Also, I would check out Harry Harrington on YouTube. He’s in the UK and has some videos about collecting on his channel: https://www.youtube.com/user/bonsai4me2
In terms of plans for the next five years I don’t know that anyone can give you a risk-free or success-guaranteed roadmap but there are tons of deciduous videos on Mirai Live that can teach you how to handle trees at all different stages of bonsai creation. I do think it’s great to keep in mind though that different parts of the tree can be at different stages. So it may be likely that some branches will be ready for refinement but some still need development.