A dwarf deciduous shrub allied to P. fruticosa. The leaves are small, usually not more than 1 in. long including the petiole, with commonly seven leaflets, the lowermost four inserted at the same point and forming a whorl (as sometimes, though not regularly, in P. fruticosa), they are linear or linear-lanceolate, acute, usually strongly revolute, grey-green above, hairy on both sides and often very densely so and white beneath. Flowers small, normally not much over 1⁄2 in. wide, borne on long, slender pedicels; bractlets of outer calyx linear-lanceolate, equalling or shorter than the sepals.
P. parvifolia was described in 1831 from a cultivated plant, introduced to the St Petersburg Botanic Garden from the region of Central Asia known as Dzungaria. It also occurs in other parts of Central Asia, in Siberia, and probably in the inner ranges of Kashmir and Pakistan. It is not in cultivation in this country in its typical state, so far as is known, and is not represented in the Kew Herbarium by an authentic specimen. The above account is based on Lehmann’s original diagnosis and figure, and on the description by Juzepchuk in the Flora of the Soviet Union. In the latter work it is acknowledged that P. parvifolia is a very variable species, and three ‘races’ are described, differing from the typical race in various characters.
The cultivated plants, which are from western China, may belong to P. parvifolia in the broad sense, but they are not typical, and may represent another race of the species. The leaves are bright green above, bluish or greyish beneath, only slightly hairy; the leaflets are obtuse or subacute, not or scarcely revolute, and often they are in fives. The flowers are 7⁄8 to 1 in. wide, sometimes larger, solitary or in condensed cymes. They are certainly very distinct from P. fruticosa, more so perhaps than is typical P. parvifolia, with which, however, they agree in their small leaves and leaflets, the latter usually in sevens.
These cultivated plants mostly derive from seeds collected by Reginald Farrer in S.W. Kansu in 1914 (No. 188), but this sending also included seeds taken from what may have been a hybrid swarm between P. parvifolia and P. davurica. ‘The deep golden type passes into the pure white by innumerable gradations of cream, amber, citron and butter-yellow – intermediate forms or hybrids; seed sent out embraces all these…’ (Farrer, The English Rock Garden, Vol. II, p. 510). The plants raised from Farrer 188 showed a similar range of colour, except that no whites were produced, but those that have been perpetuated in commerce have bright yellow flowers and show no sign of hybridity. Their naming in gardens is confused. Some bear clonal names, others are called P. fruticosa var. parvifolia or P. fruticosa var. farreri (a name attributed to Besant but not supported by a description). See further in the section on garden varieties (‘Farreri Prostrata’, ‘Klondike’, and ‘Gold Drop’). A fine form of P. parvifolia was introduced by Purdom from Shensi (see ‘William Purdom’ in the same section).
In Yunnan, and on the frontier between that province and Burma, Forrest found a form of P. parvifolia with flowers described by him as ‘deep orange’, ‘deep chrome-orange’, or ‘deep ruddy orange’. Seeds were sent by him on at least three occasions, and possibly also by Farrer during his expedition to upper Burma. Whether all the plants in a stand had flowers of this colour or just the odd one here and there is not clear from Forrest’s field-notes. There is no record of a plant raised from the wild seeds producing flowers of the colour described, but it did emerge in a later generation (see ‘Tangerine’ in the section on garden varieties). A plant in cultivation as Forrest’s form of P. fruticosa is very like the forms of P. parvifolia from Kansu except that the foliage is darker, the leaflets are always in fives, and the flowers are larger. Some specimens collected by Forrest in Yunnan and identified as P. parvifolia appear to be nearer to P. arbuscula.
P. × rehderiana Hand.-Mazz. P. fruticosa var. purdomii Rehd. (not P. purdomii N. E. Brown) – The plant described by Rehder as P. fruticosa var. purdomii was raised from seeds collected by Purdom in Shensi in 1911 under his number 848. It was considered by Handel-Mazzetti to be a hybrid between P. parvifolia and P. davurica (glabra) var. mandshurica. In raising the taxonomic status of this plant, he had to alter the epithet, since the name P. purdomii had been published by N. E. Brown in 1914 for an herbaceous species. This putative hybrid is not in cultivation in Britain, so far as is known, or at least not in commerce. For P. fruticosa ‘Purdomii’ of gardens, see ‘William Purdom’ in the section on garden varieties.