Meiwa kumquat, Fortunella crassifolia,
This is a lesser-known species of kumquat. The tree is similar to the Nagami kumquat in appearance. As with its cousin, the Meiwa trees are semi-dormant in winter, allowing them to withstand temperatures below freezing. The flowering season is in summer, and the fruits mature in late winter. The almost-round fruits are orange at maturity, up to one and one-half inches in diameter. The flesh is light orange, contains a few seeds, and is acidic.
Compared to Nagami: The sweet rind is thicker than the rind of Nagami, making it seem sweeter than Nagami.