Hypericum xmoserianum (Nomenclature)
Shrub 0-3-0-5(-0-7) m tall, bushy, semi-evergreen, with branches spreading, arching, not very frondose. Stems red, 4-lined when young, soon 2-lined to terete except immediately below nodes (4-lined); internodes 8-43 mm, shorter than to exceeding leaves; bark greyish-brown. Leaves petiolate, with petiole 1-2.5 mm long; lamina 22-60 x 7-36 mm, oblong-lanceolate or rarely lanceolate to oblong-ovate or ovate, acute to rounded-apiculate or very rarely rounded, margin plane, not incrassate, base cuneate to rounded, paler beneath, not glaucous, subcoriaceous; venation: 4 pairs main laterals, with midrib branched distally, and distinctly visible lax tertiary reticulum; laminar glands medium to short streaks and dots; ventral glands ± dense. Inflorescence 1-8-flowered, from 1-2 nodes, corymbiform, some- times with shorter apical internode, without flowering branches from middle part of stem; pedicels 2-5 mm long; bracts narrowly elliptic to narrowly oblong, deciduous. Flowers 45-60 mm in diam., stellate to slightly cyathiform; buds broadly ovoid to subglobose, obtuse. Sepals 7-10 x 6-10 mm, free, imbricate, unequal, broadly oblong-elliptic to subcircular, rounded, erect in bud, ± spreading in fruit, with margin ciliate or ciliolate, scarious, often with submarginal red zone; midrib obscure or indistinct, veins not prominent; laminar glands linear, numerous. Petals bright yellow, not tinged red, spreading or ± incurved, 21-30 x 15-20 mm, c. 3 x sepals, obovate, with apiculus subterminal to lateral, rounded; margin entire or ciliate, with few inframarginal gland dots. Stamen fascicles each with c. 50-70 stamens, longest 12-18 long, c. 0.5-0.75 x petals; anthers reddish. Ovary 6.5-9 x 5-6 mm, ovoid to ovoid-conic; styles 8-11 mm long, 1-1.5 x ovary, erect, outcurved at apex; stigmas not capitate. Capsule 9-12 x 9-11 mm, broadly ovoid. Seeds dark brown, 0.9-1.1 mm long, ± cylindric, not or scarcely carinate, shallowly scalariform-reticulate.
2n = 36 (Sugiura, 1936), c. 50 (Gibby in Robson, 1981).
Known only in cultivation.
H. x moserianum is the result of an artificial cross (H. patulum♀ x H. calycinum♂) made in c. 1887 at Moser's nursery at Versailles. It has the general habit of a low H. patulum (with low spreading branches); but the influence of H. calycinum is apparent in the subcoriaceous leaves with marked reticulate venation (visible beneath), the relatively large flowers with more spreading petals, the reddish anthers and the relatively long stamens and styles. It is partially fertile; the capsules contain a mixture of fully developed seed and flattened or shrivelled seed. From some developed seeds my wife raised a varied batch of seedlings, some of which have flowered and seem healthy. These plants show the re-assortment of characters that one would expect from F1 hybrid seed. The reported chromosome numbers of H. x moserianum (2n = 36 and c. 50) are difficult to reconcile with its known parentage. H. patulum (2n = 36) x H. calycinum (2n = 20) should give 2n = 28. Even if the record of 2n = 36 for H. patulum is based on a misidentification and that species in fact has 2n = 20 like H. uralum, the number should be 2n = 20. Only further research will resolve this apparent anomaly. If the cross was between 2n = 36 (unreduced) and n = 10, giving 3n = 46, that triploid number would not be consistent with the partial fertility of H. x moserianum.
Yates (1991) reported 6 different types of foliage in a trial at East Malling Research Station. A variegated form, in which the red sap tinges some of the white parts pink, arose spontaneously in 1894, a short time after the original cross was made. It has smaller leaves and flowers than the typical form and, although not vigorous in growth, is now widely used as a foliage plant:-