To dream of a greenhouse represents a serious attitude about developing some area of your life. An expert attempt to improve, mature, or slowly create something special to you. Isolating some area of your life so it develops without interference from others.
Negatively, a greenhouse may reflect your attempt to develop some area of your life in isolation or without others interfering when that may not be a good idea. Feeling that it may be in the best interest of your plans to responsibly isolate them from others. Considering raising children on your own.
Example: A woman dreamed of seeing a greenhouse with plants in it. In waking life she was pregnant and had broken up with her boyfriend. She was considering what it would take to raise the child on her own and be the best mother possible to the child. The greenhouse may have reflected her serious attitude about raising her child on her own. Her consideration of isolating her life away from the boyfriend and raising the child all on her own as best as she could. Feeling that it may be a responsible idea to raise the child without the ex-boyfriend’s involvement at all.