Satsumas -- or mikan as they are known in Japan -- look very similar to clementines and many people can't tell them apart. Both are varieties of mandarin oranges that are easy to peel and are usually seedless. For this reason, both make for healthy snack options that are best just eaten in hand. They do, however, have subtle differences in appearance that you can discern if you know what to look for.
The Satsuma hails from Japan, which is still the biggest Satsuma cultivating country in the world. The clementine originated in Algeria. The name comes from Father Clement Rodier, the French missionary who developed the strain in the early 20th century. Both satsumas and clementines are grown in Europe.
Clementines, like satsumas, are usually seedless, unless honeybees cross-pollinate the plants. Clementines have a deeper orange colour than satsumas, and the shape is rounder. Like satsumas, clementines have a loose rind that peels easily, but it is tighter than the satsuma's. The leaves of the Satsuma tree are typically bigger and wider than a clementine tree.
Clementines have a rich sweet, juicy taste and a spicy aroma. Satsumas, on the other hand, have a tender juicy taste that's not quite as strong as a clementine.
Satsumas are more cold resistant than most other types of citrus fruit, including clementines, and the trees have survived temperatures as low as -9C. What's more, because of their low total heat requirement, satsumas typically ripen earlier than clementines, as early as October or November.
Satsumas are very fragile and bruise easily compared to clementines. As a result, they must be handled carefully and generally do not ship well. Harvesting satsumas is quite labour-intensive because field workers have to snip each fruit individually off the tree using clippers. Just tearing a Satsuma off the tree will likely damage its skin.