This is Fortunella crassifolia, also known as Meiwa Kumquat, Sweet Kumquat, and Sweet Kinkan. This species is grown for its sweet round fruit, and fragrant flowers. This versatile tree is also used as an ornamental which can be grown indoors if needed. Growing up to 20 feet high, this tree likes to live in full sun. USDA Hardiness Zones 8 to 11.