Marumi Kumquat

UCR traces an early description of the round kumquat under the name Citrus japonica to Thunberg’s 1784 Flora Japonica; the account describes cherry-sized fruit. UCR later interprets the small leaves, axillary spines, and fruit size as indicating a round rather than an oval kumquat. This is an identification from the historical description, not a verified link to accession CRC 3237.^⁠[1]

UCR’s CRC 3237 account describes small, spherical to somewhat oblate golden-yellow fruit, with a smooth, thin, spicy and aromatic rind, sparse pulp, acid juice, four to seven sections, and one to three small seeds. It lists ripening year-round at Riverside, with timing varying by growing conditions.^⁠[1]

Grower reports describe different plants and settings. A Bavaria grower reports about 30 fruits, largest up to 35 mm, and most seedless, from a Marumi kept in a cold house. A greenhouse tasting compares one Marumi fruit with one Meiwa fruit; another short video shows a flowering plant, while a Seattle greenhouse grower reports summer and second crops. These are local observations, not replicated cultivar-wide results.^{⁠[4]⁠[6]⁠[7]⁠[8]}

In one Seattle greenhouse tasting, the speaker describes edible, sweet skin, a few seeds, and sour flesh that is “not extremely sour.” A separate greenhouse account reports winter leaf yellowing around 45–50 degrees, but gives no temperature units. A Houzz thread repeats retail claims about no damage at 10°F and leaf drop with regrowth at 0°F while asking whether they are accurate; no measured exposure or Marumi hardiness threshold is established.^{⁠[8]⁠[6]⁠[5]}