Calamondin or Variegated Kumquat
This fruit, of Chinese origin, is not a sour orange, but is perhaps a hybrid between a sour mandarin and a kumquat. It is grown mainly as an ornamental. The tree is very upright and columnar, has small mandarin-like leaves and is very cold hardy. It produces its mandarin-like fruits profusely and these hold on the tree almost all year round, giving the tree its great aesthetic appeal. The fruit is juicy and sour but not bitter and, if sweetened, can make a pleasant drink.