This is how I work out a planting for a specific site. In this case I have a space that receives full sun for most of the day on a shallow soil over chalk.
Using a ruler on one side and sketching the plants hight and habit allows me to evaluate my first ideas in terms of the desired look and feel.
More work is to be done, judging colours and how it works over a whole year. Plants are not static, so you design an evolving sculpture.
Finally the client will receive a more refined piece with all the information more neatly communicated.