Going to a nursery, or looking online, or flipping through a book of plants can be fun. At least if you are into that sort of thing. Many times no matter where we are, we are drawn to the showy plants. The ones that stand out. It is just human nature that we are drawn to them. Typically these are specimen plants. However, when planning a landscape, too many specimen plants is not a good thing.
A specimen plant per Merriam-Webster Dictionary is: a plant grown for exhibition or in the open to display its full development as distinguished from one in a border or other planting. They are to be unique. When there are too many specimen plants, it is too busy for the eye. It is good to have interest in your landscape. And it it good to have interest all throughout the year. But having too much at one time is not a good thing. A specimen is meant to be unique and the star of the show.
You need some “basic” plants incorporated into your landscape. What this will do is help to make the specimen plants pop out more. These “basic” plants are called foundation plants. Typically they do not do much more than be green and in the background. They may have a season when there is something nice about them. Overall they not the show of the landscape. But they play a key role in making the specimen plant stand out even more.
Planning a landscape can be a daunting task. But doing your research on the plants you want, and knowing what they are going to do will help to create a well rounded landscape that is not too busy.