I have looked at descriptions of normalisation but I'm not sure if I'm understanding your point. Are you suggesting I should create a table for Requirements and Tolerances? Perhaps if I explain a bit better what I'm attempting to do. I have a plant database. I have a table for each category of plant, trees, shrubs etc. I have have done it this way for the user so they can, when entering data, initially select the main category. One of the fields in each category is Requirements and Tolerances refering to the conditions for planting eg. water, wind etc. These will be different for each plant so I don't see how a separate table will help.
Again please forgive my ignorance.
Sara