The kumquat tree is a close relation to the mandarin tree and belongs to the flowering plant family Rutaceae, which originates in China and in Malaysia. Kumquat is the name given to the various species of citrus fruits in the genus Fortunella. It is also the name given to their fruit. Kumquats are small round or oval fruit which measure two to five centimetres in length. Their orange-yellow skin can be eaten, and their flesh is acidulous.