Duncan Citrus paradisi Macf. Grapefruit
It is an ancient, neither early, nor late variety that has many clones. It got its name in honor of A. L. Duncan, who brought it to Florida in 1830. It is the ancestor of almost every other variety.
This attractively looking high and wide tree with dark green leaves is considered the most cold-hardy grapefruit of all. Its fruit is larger than that of 'Marsh' cultivar (8-13cm). It is flattened with a ridge at the base and small neck. Mature tree on the plantation can produce as much as 150-200 individual fruits, sometimes even more. The fruit's rind is pale to light yellow, quite thin, smooth, slightly pebbled and easy to peel. It contains also lots of aromatic essential oils and has light yellow to yellow-brown, juicy pulp that contains 48% of juices, vitamin C (48-50mg/100ml of juices), 12-14 segments with thin membranes and 30-60 seeds. 'Duncan' tastes like typical store grapefruit with excellent and very intensive flavor. It is also the sweetest and most delicious of all grapefruits, which predetermines it to be used for juice processing. There are other, seedless varieties that are preferred for direct consumption though. It's commercially grown in India, but in general is more productive and earlier ripening than any other variety; it starts to ripen in December, but the most quality fruit can be harvested from February to March, when the ratio of acids in the fruit is much lower. The ripe fruit can hang long on the tree without any significant quality loss and together with its hardiness this makes it one of the most suitable varieties for growing in greenhouses (especially when it is grafted on Poncirus). 'Duncan' requires temperatures as low as 5°C for successful overwintering. It is also used as rootstock.