January through March is the whole ripening window for Seville oranges on UC Riverside's collection trees, and shops may stock them for only a few weeks of it. Seville orange marmalade starts with this sour orange, a seedy, bitter, acidic fruit and the traditional choice for British marmalade. Americans rarely see it fresh because California grows just 89 acres.
A sour orange grown for peel, juice and flowers
UC Riverside's Citrus Variety Collection lists "Seville orange" as a synonym for the sour orange, Citrus × aurantium, not as a variety of it. Its Seville sour orange is a medium-large, round fruit with a dark orange rind, full of seeds and sharply bitter, and the collection notes that orange marmalade has traditionally been made from it. The fruit is also valued for its oils. In Europe the blossoms are distilled for neroli, a perfume material, and in China they flavor tea.
Genetically it sits between two older citrus. A 2023 study in Frontiers in Plant Science describes sour orange as an F1 direct hybrid of pummelo and mandarin: a first-generation cross between the two.
Why the British built marmalade on it
The Sevilles in British kitchens come from Spain. Asociafruit, the Spanish growers' association, says the province of Seville remains the country's largest producer of bitter oranges. Fresh exports, sent mainly to the United Kingdom, have fallen substantially since the 1980s, though some packers still sell fresh fruit to home marmalade makers as well as to industry.
The fruit's bitterness is the point. On the British Food: A History blog, the author describes the Seville as very bitter and grown in Spain largely for British marmalade, and explains that pectin, which gels at 105°C (221°F), is what makes a marmalade set.
How long is the Seville season?
A few weeks in a shop, a few months on the tree. UC Riverside's trees ripen from January into March. Melissa's, a US specialty produce distributor that sells American-grown Sevilles, lists them from December through February.
British cooks see a similar window. The same blog called it "a small window of just a few weeks", and in a reply to a reader the author recalled that the season used to last about two weeks in January, while Sevilles now turn up from the start of December into February.
Why Seville orange marmalade is rare in the US
Acreage comes first. The 2026 California citrus acreage survey, published August 5, 2026 by CDFA and USDA's statistics service, lists 89 acres of Seville sour orange, all planted in 2018 or earlier, with no young, non-bearing trees coming on. The survey files it with navels and miscellaneous oranges, a group of 110,461 acres, so Sevilles make up less than a tenth of 1% of it.
Valencias alone cover 24,589 acres, about 276 times as much ground.
The sour orange also lost its other California job. After 1900 it was used almost as often as sweet orange as a rootstock, the root system sweet varieties are grafted onto, especially on heavy and saline soils. Then, in a manuscript on citrus rootstocks, the late UC Riverside rootstock specialist W. P. Bitters recorded that the 1946 discovery that tristeza was a virus "almost completely eliminated" further use of sour orange in the state. Sweet oranges grafted onto sour orange roots decline or die where tristeza is present.
Nor is it fruit people buy to eat. Melissa's recommends Sevilles for desserts, juices, marinades and sauces rather than eating raw, and it won't ship them to Arizona, Florida, Georgia, Louisiana, Texas or Hawaii. An American cook who wants to make Seville marmalade at home is working with a few specialty sources and a short winter.
What California makes instead
California's marmalade follows its groves, and those grow sweet citrus. Mandarins and their hybrids cover 68,536 acres in the same survey. Even Melogold, an uncommon pummelo hybrid, stands on 646 acres, more than seven times the state's Seville plantings.
None of our eight marmalades is a Seville. We make each from a single California variety, and our two oranges are winter navels and summer Valencias. For the bitter edge a Seville fan is after, our Duncan grapefruit is the most bitter jar in the range; the California marmalade guide lays all eight out on a bitterness scale, and the jars themselves are in the marmalade collection.
Photo by Jennifer Hyman on Unsplash.
