Which one is the independent variable (IV) for the following case?

The 2 variables: 1. Location of plants and 2. How the plants grow.
Lauren wants to know which location in her apartment is the best for growing African violets. She has three African violets. She puts one on the balcony, one by the kitchen window, and one on the mantel in the living room. Each plant has the same size pot and the same soil, and Lauren gives each plant the same amount of water.
A. Location of plants
2. How the plants grow