Karl Foerster is a cool season grass. Cool-season grasses grow the most in the spring, before temperatures rise over 75 degrees Fahrenheit, and again in the fall, when temperatures drop. They maintain nice color throughout the summer, but do not grow much when it is hot. Karl Foerster Grass produces fluffy blossoms in small spaces. With a mature width of 1-3 feet and a height of 3-6 feet, this plant fits into the tiny spaces in your home.