Can landscaping be done in an area with wet area or poor soils?

This is a major consideration.  Very few plants like wet feet except for plantings like Weeping Willows or Birches.  If you have a wet area, the plants can be planted higher and then topsoil used around them for a mounding effect.  This would allow you to plant in a spot with poor drainage or a wetter area.  Planting level in these types of areas will not work and the plants will typically drown out.