In the past, I replaced the tree with a jug or a stick and walked Energy Bagua around either of those. What helps is not just the tree, but more importantly the method. Thus, when it’s impossible to have a real tree, occasionally you can use an artificial tree or other objects as a substitute.
Usually, in the city, even during cold winters, trees can grow indoors. You can buy a potted tree and place it in your house, just do not get a thorny tree. Some practitioners asked me: “My family has a tall cactus. It’s the only plant in my home. Can I put it in the center for Energy Bagua?” My suggestion is that it’s best not to get close to it, because if you accidentally touched it, you would be covered with little spines or you could hurt your eyes. That’s not good. Everything must be done for health and safety. That is to say, we should be always focused on people and safety first.