Portraits can be shot with a lens of any focal length. It is up to you to decide what tools work best to achieve the desired image to express your concept. If the lens is too short for what you want, then the lens is too short. I would not say that it is too short in general, however. Most of my favorite portraiture was shot with normal to medium-wide lenses. If you want to do commercial head shots or glamor photography specifically, the normal lens might give you effects that you are not looking for with many models in tight compositions...but for general-purpose portraiture it is just fine.
FWIW, most of my favorite landscape shots are also either shot with normal lenses, or short or long lenses that are just a moderate distance from a normal lens. Perhaps 35 - 70, speaking in 35mm terms.