Hawthorn progression into a Bonsai tree
This case study shows the training of a Hawthorn after being collected from a forest. The trunk was very straight, had no branching and had little going for it other than some quite mature bark. The tree was planted into a shallow terracotta container and left to recover.
The first picture shows the hawthorn, around 3 meter (10ft) tall, which was collected from the forest.
The second picture is taken about one year and a half later, the trunk was cut back to 12 cm (4’’) and a short, hollow trunk was created.
Picture 3: The tree recovered well from chopping and the trunk could be carved out. The new shoots were regularly pruned back to create the branch structure. Training the tree took 5 years.

More information
Source: Harry Harrington (Bonsai4me.com)
Go to the Bonsai progression forum.