This species (in the broad sense) is extremely variable and has a wide range in S. America from Costa Rica to Chile. In his monograph, Dr Sleumer divides it into a number of varieties, while admitting that these are linked by intermediates or perhaps by hybrids and scarcely merit the status of variety. In his article accompanying Bot. Mag., n.s., t. 127, B. L. Burtt suggests that P. prostrata is best divided into two subspecies, ‘each containing a considerable range of minor variation’. Of the two subspecies, the typical one (i.e., containing the type of P. prostrata) is discussed later in this entry. The cultivated plants belong mainly to the subsp. pentlandii:
subsp. pentlandii (DC.) B. L. Burtt P. pentlandii DC.; P. purpurea subsp. pentlandti (DC.) Ktze.; P. angustata Benth.; P. purpurea subsp. subsetosa Ktze. var. angustata (Benth.) Ktze.; P. prostrata var. angustata (Benth.) Sleum.; P. prostrata var. pentlandii (DC.) Sleum., nom. illegit.; P. poeppigii (DC.) Klatt; Gaultheria poeppigii DC. – A dwarf evergreen shrub, sometimes prostrate; young shoots downy and sparsely bristly. Leaves shortly stalked, oblong-ovate, pointed, rounded or tapered at the base, bristly toothed, 1⁄2 to 3⁄4 in. long, 1⁄8 to 1⁄4 in. wide, dark glossy green and glabrous above, pale green and either glabrous or with a few dark bristles on the midrib beneath; there may be ten or more leaves to the inch. Flowers solitary in the leaf-axils, nodding, opening in June. Corolla ovoid-globose, white, 1⁄3 in. long, contracted towards the mouth and there dividing into five pointed, recurved lobes. Stamens ten, with downy stalks swollen at the base; anthers with four short bristles. Calyx-lobes ovate, pointed, becoming, at any rate sometimes, swollen at the fruiting state and turning blue-purple. This is the colour also of the globose berry, which is 1⁄4 to 3⁄8 in. wide, nodding, with the remains of the stigma at the top and the usually fleshy lobes of the calyx at the base.
The subsp. pentlandii has broadly the same range as P. prostrata as a whole. It was originally described by de Candolle (as a species) from a specimen collected by Pentland in Bolivia. The description given above is made from a form which still grows at Wakehurst Place in Sussex, and is perfectly hardy. There is another slightly differing form in cultivation which appears to have been distributed originally under the name “Pernettya nigra”. It is a more robust plant than the one described, with trailing or arching branches and leaves up to 1 in. or slightly more long. This is the form figured in Bot. Mag., n.s., t. 127, from a plant in the late Sir Frederick Stern’s garden at Highdown in Sussex. The plants there were killed in the severe winter of 1946-7, but similar plants at Borde Hill, also received as “P. nigra”, were completely hardy and made a thicket about 1 ft high and 15 ft wide.
In the plants considered above, the fruits are almost black when ripe. But in some at least of the Chilean plants they are pink or even white. A pink-fruited form was introduced by Comber under his number 1113 and makes at Wakehurst Place an erect shrub about 21⁄2 ft high. A low-growing form of the subsp. pentlandii, with white fruits, received an Award of Merit when shown from the R.H.S. Garden at Wisley in September 1957. It was stated, erroneously, to have been raised from seeds collected by E. K. Balls in Mexico.
The typical subspecies of P. prostrata (subsp. prostrata) differs from the subsp. pentlandii in its relatively broader and shorter leaves. It is figured in Bot. Mag., t. 6204, from a plant introduced by Anderson-Henry from the Andes of Quito, Ecuador. This proved to be hardy and bore fruit.
P. ciliata (Cham. & Schlecht.) Small Gaultheria ciliata Cham. & Schlecht.; P. pilosa (Graham) G. Don; Arbutus pilosa Graham; P. buxifolia Mart. & Gal.; P. hirsuta (Mart. & Gal.) Camp; P. mexicana Camp – Closely allied to P. prostrata, which it replaces north of the equator between 15° and 20° N., and, like it, is very variable. According to Sleumer it is not separable from P. prostrata by any one character, but in some forms the branchlets are densely bristly and the leaves ciliate. Although introduced early in the last century (Bot. Mag., t. 3177) the cultivated plants mostly derive from seeds collected by E. K. Balls in Mexico in 1938, on Mt Malinche and Popocatepetl (Bot. Mag., n.s., t. 66).
P. ciliata appears to be quite hardy in cultivation. It occurs in Mexico at altitudes of 7,000 to 10,000 ft.