Nagami Kumquat

The oval kumquat or Nagami kumquat[7] (Citrus margarita or Fortunella margarita if dividing Eufortunella kumquats into separate species) is ovoid in shape and typically eaten whole, skin and all. The inside is still quite sour, but the skin has a very sweet flavour, so when eaten together an unusual tart-sweet, refreshing flavour is produced. The fruit ripens mid- to late winter and always crops very heavily, creating a spectacular display against the dark green foliage. The tree tends to be much smaller and dwarf in nature, making it ideal for pots and occasionally bonsai cultivation.

The ‘Centennial Variegated‘ kumquat cultivar arose spontaneously from the oval kumquat. It produces a greater proportion of fruit to peel than the oval kumquat, and the fruit are rounder and sometimes necked. Fruit are distinguishable by their variegation in color, exhibiting bright green and yellow stripes. The tree is distinguishable by its lack of thorns.[8]

 

https://en.wikipedia.org/wiki/Kumquat#Oval_kumquat