Kumquats are a group of small fruit-bearing trees in the flowering plant family Rutaceae, either forming the genus Fortunella, or placed within Citrus sensu lato. The edible fruit closely resembles that of the orange (Citrus sinensis), but is much smaller and oval, being approximately the size and shape of an olive.

They are slow-growing evergreen shrubs or short trees, from 2.5 to 4.5 metres (8 to 15 ft) tall, with sparse branches, sometimes bearing small thorns. The leaves are dark glossy green, and the flowers pure yellow, similar to other citrus flowers, borne singly or clustered in the leaf-axils. The kumquat tree produces 30 to 50 fruit each year. The tree can be hydrophytic, with the fruit often found floating on water near shore during the ripe season.

The plant is native to south Asia and the Asia-Pacific. The earliest historical reference to kumquats appears in literature of China in the 12th century. They have long been cultivated in Japan, Taiwan, the Philippines and southeast Asia. They were introduced to Europe in 1846 by Robert Fortune, collector for the London Horticultural Society, and shortly thereafter into North America. Source: http://en.wikipedia.org/wiki/Kumquat