Introduction & History

Before the Ruby Reds and Star Rubys and Rio Reds transformed grapefruit into a palette of pinks and reds, there was the Thompson — the original pink grapefruit that proved consumers would pay more for colour in their breakfast fruit. Discovered in 1913 in Oneco, Florida, by W.B. Thompson as a bud sport on a Marsh Seedless white grapefruit tree, the Thompson (also called Marsh Pink or Pink Marsh) showed the first hint of pink pigmentation in the grapefruit world. That slight blush — barely perceptible by modern standards — was enough to spark the coloured grapefruit revolution that would eventually remake the industry. Every subsequent pink and red grapefruit variety traces its lineage through the Thompson mutation.

History & Origin

Found in 1913 by W.B. Thompson on his property near Oneco (now part of Bradenton), Florida, as a limb sport on a Marsh Seedless grapefruit tree. The mutation was subtle — just a light pink flush in the flesh — but commercially significant as it distinguished the fruit from standard white grapefruit. Thompson patented his discovery and propagated it commercially through Florida nurseries. By the 1930s, Thompson Pink was widely planted across Florida and Texas. However, its light pigmentation was quickly overshadowed when Red Blush appeared in Texas in 1929 with much deeper colour. Thompson Pink remains in older Florida orchards but is no longer planted commercially, replaced by deeper-coloured varieties.

Botanical Description

A large, vigorous evergreen tree reaching 7–8 m with a broad, dense, rounded canopy. Leaves are large, broadly ovate, dark green, and leathery. Flowers are white, large, and highly fragrant. Fruit is large (10–13 cm), round, with yellow rind that may show a faint pink tinge — significantly less rind colour than Red Blush or Star Ruby. Flesh is light pink — distinctly coloured compared to white Marsh Seedless but pale compared to modern red grapefruits. Juice is very slightly pink-tinged. Seeds are few (0–6), approaching seedlessness. The tree is extremely vigorous and productive, often outperforming more pigmented sports in total yield.

Planting & Cultivation

Plant in full sun in deep, well-drained soil. The very vigorous tree needs ample space — allow 8 m between trees. Plant in spring in frost-free locations. Thompson thrives in Florida's humid subtropical climate and in hot, semi-arid Texas conditions. Apply generous mulch. The tree establishes quickly and grows rapidly on vigorous rootstocks. Irrigate regularly during establishment. Thompson's extreme vigour means it reaches bearing size faster than most grapefruit varieties — expect first fruit within 3 years of planting.

Cultivation

Manage as standard grapefruit with the understanding that Thompson's pink colour is subtle and cannot be intensified significantly through cultural practices. Apply complete citrus fertiliser 3 times per year. The vigorous growth may require more pruning than less vigorous varieties to maintain manageable tree size. As the ancestral parent of all pink/red grapefruit, Thompson is primarily of historical and genetic interest rather than current commercial value. The near-seedless fruit has excellent eating quality regardless of its light colour.

Climate & Cold Protection

Suited to hot subtropical climates (USDA zones 9b–11). Cold tolerance is approximately -2°C on fruit, -4°C on wood. Like all grapefruit, Thompson requires significant summer heat for quality fruit. Florida's humid climate produces the largest, juiciest fruit. Texas heat intensifies whatever pink colour exists. The tree's extreme vigour gives it good recovery ability after moderate freeze damage.

Seasonal Care

Spring: Bloom; fertilise; begin irrigation. Summer: Maximum heat; irrigate consistently. Autumn: Fruit approaching maturity; begin harvest of early fruit. Winter: Main harvest; freeze protection in vulnerable areas. Thompson holds well on the tree, extending the harvest over several months.

Cold Protection

Standard grapefruit freeze protection: wind machines for commercial orchards, microsprinklers for smaller plantings, trunk wraps for young trees. The vigorous growth provides rapid recovery after moderate freeze events. In Florida's increasingly rare but devastating freeze events, Thompson on vigorous rootstock often recovers faster than other grapefruit varieties.

Seasonal Care Calendar

Propagation

Propagated by budding onto standard grapefruit rootstocks. Sour orange was the traditional Florida rootstock; Swingle citrumelo and Carrizo citrange are modern alternatives with CTV tolerance. Thompson's vigorous growth means it establishes quickly on rootstock. Certified budwood is available through Florida's Division of Plant Industry nursery inspection programs. Historical importance: Thompson budwood was the source material from which all subsequent pink and red grapefruit mutations were derived.

Diseases & Pests

In Florida, HLB (citrus greening) is the existential threat to all grapefruit including Thompson. Aggressive Asian citrus psyllid management is essential. Citrus canker is also present in Florida. Melanose on fruit. Scale insects and whitefly. Root rot on susceptible rootstocks in Florida's wet conditions. The thick rind provides natural protection against mechanical damage and fruit fly entry.

Harvesting & Culinary Uses

Fruit matures from November through March in Florida. Harvest when internal quality reaches eating standard: Brix 9–11 with acid ratio above 6:1. The light pink colour is not a useful harvest indicator — colour peaks early and then stabilises while internal quality continues improving. Fruit holds on the tree for 3–4 months, improving in sweetness. Near-seedless fruit segments cleanly for eating. Store at 10°C for up to 6 weeks.

Culinary Uses

Thompson Pink grapefruit is excellent for eating fresh — the near-seedless segments and mild grapefruit flavour make it an easy breakfast fruit. The juice is pleasant with a lighter colour than modern red varieties. Use in salads, cocktails (classic Greyhound), and desserts. The historical significance makes Thompson interesting for heritage citrus tasting events alongside its more colourful descendants.

Rootstock Guide

Swingle citrumelo is the current Florida standard for Phytophthora resistance and CTV tolerance. Carrizo citrange provides good nematode resistance. Sour orange produces the finest fruit quality but is deadly with tristeza. Rough Lemon gives extreme vigour on sandy soils but coarser fruit. Volkameriana for rapid establishment. In Texas, Carrizo citrange is preferred.

Container & Companion Growing

Container Growing

Not suitable for containers due to extreme vigour and large tree size. Thompson is among the most vigorous grapefruit varieties and even on dwarfing rootstock produces a tree too large for practical container management. For container grapefruit, consider the smaller Cocktail grapefruit instead.

Companion Planting

In Florida orchards, plant native flowering species (Bidens alba, Coreopsis) to attract parasitoid wasps for biological pest control. Thompson's large canopy provides shade for understory plantings. In home landscapes, the impressive size makes Thompson a statement tree — plant as a specimen with adequate clearance from structures.

Common Mistakes to Avoid

Expecting vivid pink colour — Thompson's pink is very light by modern standards. Planting in mild-summer areas where grapefruit doesn't sweeten. Not appreciating the historical significance when marketing or growing this variety. Growing in containers — the extreme vigour makes this impractical.

Frequently Asked Questions