In 1750 Griffith Hughes described a fruit he called the "forbidden fruit" of Barbados. That was the grapefruit, and the types of grapefruit sold today sort by flesh color: white (Duncan, Marsh), pink (Thompson), red (Ruby Red, Star Ruby, Rio Red, Flame), plus pummelo hybrids such as Oroblanco and Melogold.
The grapefruit is a young fruit by citrus standards. Botanists first took it for a sport of the pummelo, then, from about 1948, for an accidental hybrid of pummelo and sweet orange, which is why it is now written Citrus × paradisi, as Julia F. Morton's 1987 book Fruits of Warm Climates records. American horticulturists disliked the name "grapefruit" enough to push for "pomelo" instead, and in 1962 Florida Citrus Mutual floated a new name to lift sales. The public protested, and the idea was dropped.
The main grapefruit varieties at a glance
Grapefruit has a high heat requirement: Marsh is commercially restricted to very hot climates; Rio Red does well in the Coachella Valley for that reason. Seasons below are from the University of California's collection at Riverside, except Thompson's, which is from Morton.
| Variety | Flesh | Where and when it began | Season |
|---|---|---|---|
| Duncan | White (buff) | Seedling near Safety Harbor, Florida, about 1830; named in 1892 | January–May |
| Marsh | White (buff) | Chance seedling near Lakeland, Florida, about 1860 | January–May |
| Thompson (Pink Marsh) | Pink, faded to nearly amber by late March | Branch of a Marsh tree at Oneco, Florida, 1913 | Color best January–February |
| Redblush / Ruby Red | Red, with a crimson blush on the rind | Branch of a Thompson tree, McAllen, Texas, 1929 | February–June |
| Star Ruby | Very dark red | Irradiated seed, Texas A&I, 1959; released 1971 | February–June |
| Rio Red | Dark red, darkest next to the membranes | Bud sport from irradiated Ruby budwood, Texas | February–June |
| Flame | Nearly as dark as Star Ruby | Seed of a Ruby Red sport from C. Henderson's grove in Houston, Texas; selected by C. J. Hearn, released 1987 | February–June |
| Oroblanco | Very pale yellow | UC Riverside cross, 1958; released 1980 | Early December–March |
| Melogold | Pale yellow | Sister of Oroblanco; released 1986 | Early December–March |
Sources: Morton for Thompson; UC Riverside's Citrus Variety Collection for the rest (Duncan, Marsh, Redblush, Star Ruby, Rio Red, Flame, Oroblanco, Melogold).
White grapefruit, the seedy original and the seedless one
Duncan is thought to be the country's oldest grapefruit variety. The parent tree grew near Safety Harbor on Florida's Pinellas Peninsula from seed planted by Count Odet Philippe (older sources spell it Odette Phillippe), the man credited with bringing grapefruit to Florida, and A. L. Duncan of Dunedin named and introduced it around 1892. It carries 30 to 50 seeds per fruit, and Morton calls the peel "highly aromatic". Tasters at UC Riverside in 2009 wrote "rich, fruity, intense, less bitter; seedy."
The Citrus Industry (1967) called Duncan "the standard of grapefruit excellence in Florida" even as seedless varieties pushed it out of the fresh market. Its flavor and its suitability for canning kept it planted.
Marsh was the one that pushed. It sprouted by chance on a farm near Lakeland around 1860, and its value went unnoticed until 1886, when a nurseryman named E. H. Tison began propagating it; C. M. Marsh, who bought the nursery, gave it his name. It was the first seedless grapefruit variety discovered, though "seedless" is relative: Morton allows it none or 3 to 8 seeds per fruit. It holds unusually well on the tree and stores well, and it became the world's leading grapefruit variety, with a flavor UC Riverside calls "good though not so pronounced as in some seedy varieties."
Where did pink and red grapefruit come from?
Most of them trace back to Marsh, through branches that mutated on otherwise ordinary trees, and they took over the market in the twentieth century.
- 1913: one branch of a Marsh tree owned by W. R. Thompson in Oneco, Florida, bore pink, seedless fruit. It became Thompson, or Pink Marsh. A similar branch appeared at Riverside around 1920.
- 1929: A. E. Henninger of McAllen, Texas, found a Thompson branch with much redder flesh. He patented it in 1934 as Ruby, U.S. Plant Patent No. 53, the first citrus variety known to receive a patent. A near-identical sport found by J. B. Webb in 1931 became Redblush, and UC Riverside treats the two as one.
Those early pinks had limits. Thompson's color is strongest in January and February and fades to nearly amber by late March, and Morton notes that Redblush juice is unsuitable for canning because it tends to turn brown with age.
Texas breeders then tried radiation, starting from a different line. Hudson was a red, very seedy grapefruit from a branch sport noticed at San Benito, Texas, in the mid-1930s, on a pink-fleshed variety that had itself begun as a sport near Ellenton, Florida, in 1906. At Texas A&I in Weslaco, Hudson seeds were irradiated in 1959, and one seedling was introduced by Richard Hensz in 1971 as Star Ruby. It is three times more colorful than Ruby Red, by Morton's account, with firmer flesh, a little more sugar and acid, and at most nine seeds. It is also hard to grow, with greater susceptibility to phytophthora, nutrient deficiencies, cold and pests, per UC Riverside. Rio Red came out of the same Texas program, as a bud sport of a tree grown from irradiated Ruby budwood. Flame, grown from seed of a Ruby Red sport, selected by C. J. Hearn and released in 1987, has color almost as dark as Star Ruby on a vigorous tree reported to be more cold-tolerant.
Which grapefruits are crossed with pummelo?
Oroblanco and Melogold taste milder than a classic grapefruit because their pummelo parent was essentially acidless. In 1958, UC Riverside geneticists J. W. Cameron and R. K. Soost crossed a nearly acid-free pummelo with a white, seedy grapefruit that had double the usual chromosomes. The seedlings that came out were triploids, and two of them were kept. Oroblanco, released in 1980, is seedless and mild and sweet, with a thick greenish-yellow peel. Its rind and membranes keep the pummelo's bitterness, but Morton notes the sections skin easily, so the membrane is easy to leave behind. Oroblanco and the tangelos also appear in our short survey of specialty citrus in California.
Melogold, its sister from the same 1958 cross, followed in 1986. It is the larger of the two, averaging 470 grams at Riverside to Oroblanco's 360 and Marsh's 280, and UC Riverside considers it a fruit for California's inland districts rather than the hot desert.
In Israel the same kind of fruit is marketed as Sweetie; Morton records the Citrus Marketing Board of Israel releasing it in 1984, with grapefruit looks and a sweet flavor.
Two fruits sold as grapefruit that aren't
Cocktail "grapefruit" is a pummelo × Frua mandarin cross made at Riverside, perhaps in the 1950s. It was never officially released and, in the words of its UC Riverside record, "escaped" into the nursery trade under a name a nurseryman probably gave it. Under its thin yellow skin the yellow-orange flesh is seedy and exceptionally juicy. Its Riverside season runs from January into March.
Chandler is a pure pummelo, not a grapefruit, bred at UC Riverside from two Siamese pummelos and released in 1961. It is large, thick-rinded and pink-fleshed, and it ripens December to February at Riverside, per its record.
Which types of grapefruit make the best marmalade?
Thick, aromatic peel and real acidity: among grapefruits, that points to the old white Duncan. Grapefruit peel is also an important source of pectin, Morton notes, and Australia was already processing grapefruit into marmalade commercially when she wrote in 1987.
Either of our grapefruit jars next to a salty blue is the boldest match on a board, per our cheese pairing notes, but the two sit far apart on bitterness. Duncan Grapefruit Marmalade is our most bitter, made from the seedy heirloom that seedless growers left behind, with soft tannin and a finish of maraschino cherry. Melogold Grapefruit Marmalade, from the pummelo cross bred for mildness, keeps the grapefruit aroma with much less bitterness and opens on blackberry.
Photo by Mustafa akın on Unsplash.
