Kumquats or cumquats 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 it is much smaller and ovular, being approximately the size and shape of an olive. The English name “kumquat” derives from the Cantonese word “gam gwat”.
The round kumquat (also Marumi kumquat or Morgani kumquat) is an evergreen tree, producing edible golden-yellow colored fruit. The fruit is small and usually round but can be oval shaped. The peel has a sweet flavor but the fruit has a sour center. The fruit can be eaten cooked but is mainly used to make marmalade and jelly. It is grown as an ornamental plant and can be used in bonsai. This plant symbolizes good luck in China and other Asian countries, where it is sometimes given as a gift during the Lunar New Year. It’s more commonly cultivated than most other kumquats as it is cold tolerant. It can be kept as a houseplant.
When the kumquats are divided into multiple species the name Fortunella japonica (Citrus japonica) is retained by this group.
Fortunella margarita, also known as the oval kumquat or the Nagami kumquat, is a close relative to Citrus species. It is a small evergreen tree, that can reach more than 12 ft (4 m) high and 9 ft (3 m) large. It is native to southeastern Asia, and more precisely to China. The oval kumquat has very fragrant citrus-like white flowers, and small edible oval orange fruits. The oval kumquat is an ornamental little tree, with showy foliage, flowers and fruits. It is also fairly frost-hardy, and will withstand negative temperatures such as 14 °F (-10 °C), and even a little lower for very brief periods. It can be grown in USDA hardiness zones 9 and warmer, but can also be tried in sheltered places, in USDA hardiness zone 8. Unlike most citrus species, the oval kumquat has a shorter growth period, and goes into dormancy fairly earlier in autumn. This partly explains its better frost hardiness.