Planted these about a year ago. What’s the fastest way to get trunk girth on these? Take out of the planter and put them into the ground? Do I just let this grow grow without pruning ?
The fastest growth in girth comes from unrestrained apical growth without setback from pruning or repotting generally!
The exceptions would be if putting them in the ground meant, poorer soil conditions, less care or shorter growing season.
If your climate is fine for that species year round then i would do some root work in large containers for the first year or two and then plant in the ground or a very large container and let it go unrestrained.
The reasoning is to set a pattern for root growth early on rather than have to correct too much after ground growth. Hope these comments help.
Plants look healthy. if you want them to develop seperately you may wish to provide seperate containers for them. The roots can get pretty entertwined over a growing season in a flat like that.