8b

Kinkoji (Citrus obovoidea), sold in Texas as Bloomsweet grapefruit, is an old Japanese citrus of unknown parentage, most likely a pummelo × mandarin hybrid. Growers report that mature trees survive about 14 to 15°F (−10 to −9°C), which makes it one of the more cold-tolerant grapefruit-type citrus, though its hardiness has never been measured in a published trial. The vigorous tree reaches 10 to 13 ft (3 to 4 m). Its large, yellow-orange fruit, round to slightly pear-shaped with a thick rind, ripens from late fall into winter; the juicy flesh is mildly acidic and not bitter, with 10 to 15 seeds. Good fresh, juiced or made into marmalade. Best suited to USDA zones 8b and 9 on a trifoliate-type rootstock.