Citrus depressa (Citrus × depressa, formerly C. pectinifera, Okinawan シークヮーサー or シークァーサー shiikwaasaa, Japanese ヒラミレモン hirami remon), in English sometimes called Taiwan tangerine, flat lemon, hirami lemon, or thin-skinned flat lemon, is a small, green citrus fruit rich in flavonoids and native to Taiwan and Okinawa, Japan. Very sour, it is often used like lemon or lime to garnish dishes, but is also used to make jam, or a yellow juice, which can be thinned or sweetened.
Citrus depressa is grown in Taiwan and Ryukyu Islands. This flat lemon is a flowering tree with an average height of 5m. The appearance is similar to Calamondin. The flowers, white and about 3cm in diameter, usually bloom in April. The fruit, which appear around July, weigh about 25~60g. Unripe, the skin is a dark green, which becomes yellow during ripening. The fruit have a very low sugar content and are very sour.