Also sometimes called gin berry, this tree can be either a small tree or a shrub. It grows to heights of 15 feet as a tree. The common juniper was used by Native Americans as an insect repellant and by the Europeans and Iroquois as a diuretic. It was also used for treating rheumatism, digestive problems, headaches and colds, as well as to make the first kind of gin. The common juniper grows best in dry, open areas. Its needles are very short, only 0.3 to 0.7 inches long.