Within the Punica granatum article...

var. nana (L ) Pers.

P. nana L. Dwarf Pomegranate

Of dwarfer stature than the normal form, and smaller in its leaves (which are often relatively narrower than usual), and also in its flowers and fruits. Bot. Mag., t. 634.The first description of the dwarf pomegranate under the Linnaean system of nomenclature was published by Linnaeus himself in 1762 (Sp. Pl., ed. 2, p. 676). This original form had been introduced to France at the end of the 17th century from the West Indies, where it was used as an ornamental hedging plant. Presumably it arose there as a mutation from the original stock brought from the Old World by the early colonists. This New World form had reached Dr Sherard’s garden at Eltham in Kent by 1723 and was known to Philip Miller. He called it the dwarf American pomegranate and said that, unlike the normal European kind, it was too tender to survive our winters, but would bear flowers and fruits if kept under glass in moderate heat, and would grow to about 3 ft in a pot. ‘The Fruit of this Kind’, he wrote, ‘is rarely much larger than a Walnut, and not very pleasant to the Taste.’The dwarf pomegranate in commerce at the present time is probably of independent origin, since it is only slightly tender and survived the winters of 1961-3 in many gardens. It comes true when raised from seeds, which are available from seedsmen, and received an Award of Merit when shown by Messrs Sutton in 1936 as a coolhouse plant. It is advisable to grow it to flowering size in a greenhouse (three or four years) before planting it outside at the foot of a sunny wall.