Citrus japonica - Family: Rutaceae
 
The cumquat (kumquat) is an evergreen shrub or small tree. It is usually grown as an ornamental, but the fruit can be used skin and all to make marmalade and also candying, where they are infused in a sugar syrup. That can then be made into a sweet liqeuer.
 
Nagami - Oval shaped fruit, very sweet, but is quite slow grower.
 
Mertifolia Chinotti - has a highly ornamental and upright growth habit with dark green shiny foliage. The fruit is a yellowy orange colour and it has small pointed leaves. Great for standardising and makes an excellent pot plant.
 
Variegated - unusual foliage with fruit that starts with white stripes which turn orange when ripe.