Citrus halimii

Citrus halimii or Mountain citron is a sour fruit variety belonging to the citrus papedas, not related to the true citron. It was first discovered and catalogued in 1973. Citrus halimii is quite rare and poorly studied. After its initial 1973 discovery and description, it has been observed in only a handful of locations scattered across Southeast Asia: Thailand and Malaysia (the locations of the first discoveries), along with isolated stands in Indonesia. Citrus halimii is a midsized evergreen tree, with a mature height of 20 to 25 feet; it is somewhat less thorny than other citrus. Like other papedas, the halimii has relatively large leaves, with a long, winged petiole. The fruits of C. halimii are edible, but sour. They are round and small, measuring about 5–7 cm in diameter. The rather thick rind eventually ripens to yellow or orange-yellow; internally the rind is tightly bound to the flesh. The yellow-green segments are filled with a number of large seeds, and a small quantity of juice.