Flame Grapefruit

USDA released Flame in 1987. Accounts of its early history differ. The 1995 register reports a Henderson seedling found at A.H. Whitmore Foundation Farm in 1973 and selected by C.J. Hearn in 1980; da Graça et al. report a Henderson seedling found in Florida in 1983. IDtools says Florida seedlings came from Henderson material originating in Texas, while UCR traces its accession to seed from a Ruby Red sport in C. Henderson’s Houston grove. These reports do not establish the exact seed-collection and planting sequence or embryo origin.^{⁠[4]⁠[2]⁠[5]⁠[1]}

Descriptions vary by source. UCR describes a vigorous, large tree and pink-red flesh beneath smooth yellow skin, with color fading after maturity. IDtools describes a compact, dense, nonweeping crown and fruit as broad as long or longer than broad, with slightly rough, leathery yellow-orange rind and red to purplish flesh; the 1995 register calls the fruit globose and seedless. Hale Groves describes Flame flesh as redder and its rind blush pinker than Ruby Red.^{⁠[1]⁠[4]⁠[5]⁠[6]}

Grower reports reflect individual trees and settings. An Arizona gardener said her tree was usually ready in early January and sometimes retained fruit until March or April. A container grower described one 2015 fruit as “incredibly sweet,” while a Pennsylvania greenhouse grower described an accidentally detached first fruit as juicy. These accounts do not establish a general harvest window or taste profile.^⁠[9]⁠[8]

Citrus Industry reported an unnamed bud sport discovered in ordinary Flame as a distinct derivative selection. Its reported improved HLB tolerance applies to that derivative, not to ordinary Flame.^⁠[7]

The 2007 karyotype study used CMA/DAPI staining and rDNA-FISH. Its abstract reports Flame Grapefruit in a marker group with three C-type and five D-type CMA-positive marker chromosomes and five 45S rDNA sites; it also reports two 5S rDNA-bearing chromosomes in each accession examined. These marker patterns are not a ploidy determination, full chromosome count, shared cultivar identity or proof of parentage.^⁠[10]