Rocky Mountain Juniper has two types of foliage: young trees have sharp, awl-shaped needles, while mature trees develop small, overlapping, scale-like leaves that are pressed tightly to the twigs, often with a blue-green, gray-green, or whitish cast, sometimes with a visible resin dot on the back. These evergreen leaves are arranged in opposite pairs, giving the twigs a flattened appearance initially before they round out with age, making them distinct from true pines or firs.