Hypericum ×inodorum Mill. (= H. androsaemum × H. hircinum; syn.: H. elatum Ait.) (Cult.) – A rare but possibly under-recorded escape from or relic of cultivation. In the second half of the 19th century apparently locally more or less naturalized, for instance near Pailhe (Saint-Lambert; ditches and shrubland, at least between 1864 and 1877). Also claimed as naturalized in Soiron in the 1880’s (off ramp near castle). Furthermore collected in Leuven (1862), Houtain (1884), Ways (1865), etc. In the 20th century much decreasing and only exceptionally collected. Recorded, for instance, in Hoogstraten in 1920. Since 2000 more often seen, at first on an old brick quay of river Leie in Kortrijk (locality now demolished), subsequently in several additional localities. See here for an overview of records: http://waarnemingen.be/soort/view/156958. At least part of these records, however, and maybe even a majority of them, may be erroneous (confusion with H. androsaemum; see below). In recent times Hypericum ×inodorum has been reliably recorded for instance from Brugge and Moen.
Hypericum ×inodorum is an exceedingly variable species and extreme forms of it much approach H. androsaemum on the one hand and H. hircinum on the other, depending on which subspecies is involved of the latter. Plants with relatively bigger petals and longer styles may look a lot like H. hircinum, especially its subsp. cambessedesii (Nyman) Sauvage (syn.: H. cambessedesii (Nyman) Cosson ex Marès & Vigin.). However, in H. hircinum sepals drop very early after flowering while they persist until and often even after fruit ripens in H. ×inodorum. Contrary to what is generally admitted, in some forms of H. ×inodorum the smell of goats characteristic of H. hircinum can be quite apparent (which is not surprising, its putative parents both usually smelling of goats, although in various degrees and often more prominently so when dry). Other extremes, i.e. plants close to H. androsaemum, are sometimes hard to distinguish from the latter, especially in style and petal length. In cultivation there seems to be a continuum between H. androsaemum and H. hircinum and it is unclear what H. ×inodorum exactly stands for. Perhaps more than one taxon is involved. With its genuine berries, H. androsaemum is probably much more easily dispersed by birds and more likely to be found as an escape in woodlands and similar habitats than H. ×inodorum.
The form of Hypericum ×inodorum most frequently encountered in Belgium, in gardens as well as in the wild, seems to be cv ‘Elstead’, with capsules becoming bright red during maturation.
Belgian records were formerly referred to as Hypericum elatum. This is a large-flowered form of this hybrid, apparently involving Hypericum hircinum subsp. majus (Ait.) N. Robson as one of the parents.
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Selected literature:
Ramos Núñez A. (1984) Taxonomía de Hypericum hircinum L. var. Cambessedesii (Cosson ex Barcelo) Ramos. Collect. Bot. 15: 369-376.
Robson N.K.B. (1985) Studies in the genus Hypericum L. (Guttiferae), part 3. Bull. Brit. Mus. Nat. Hist. 12: 163-325.
Robson N.K.B. (2012) Studies in the genus Hypericum L. (Hypericaceae). 9. Addenda, corrigenda, keys, lists and general discussion. Phytotaxa 72: 1-111.