u/Adventurous_Okra245

3ish years ago I transplanted two volunteer trees into large pots; A maple and a white pine. They have successfully endured two Iowa winters outdoors. I’m currently renting and don’t want to commit them to the earth yet. I don’t have any larger pots to move them into. Should I try to bonsai these trees?

Edit: I have learned from wiser folks that I have a silver maple and a juniper/red cedar