Hemerocallis is a genus of ca. 15 species, most originally native in East Asia (especially China and Japan). It is much grown for ornament in gardens although perhaps slightly decreasing in recent times. The species are quite often remarkably reluctant to flower in the wild, possibly as a result of strong clonal growth (see also Adolphi 1995). As a consequence, the exact identity of many populations remains doubtful. The usual garden throw-out is a vigorous plant, regenerating fast by vegetative growth (for instance in coastal dunes between De Haan and Wenduine, near Koksijde and doubtlessly elsewhere). This behaviour is typical of Hemerocallis fulva, which is believed to be the species most frequently encountered in the wild in Belgium.
Even flowering plants are sometimes difficult to identify. The plants usually grown in gardens often differ considerably from wild plants. They originated in cultivation and are usually complex hybrids. More than 38.000 cultivars are registered within the genus (Straley & Utech 2002). The two species (and/or their hybrids) treated here are the usual garden plants. A more detailed account of the cultivated plants in the genus in Europe is given by Campbell & Cullen (1986) and Jäger & al. (2008).
The identity, chorology and potential invasive behaviour of Hemerocallis in the wild in Belgium are very poorly known. It is hardly represented in herbaria and surely requires further study. Given its often expansive growth in natural habitats (mainly coastal dunes) a better understanding of the genus appears to be highly desirable.
- Tepals orange (tawny, rarely reddish-purple), 8-10 cm long, reticulate-veined. Flowers not fragrant. Fruits not or rarely developed === 1. Hemerocallis fulva
- Tepals yellow, 6-8 cm long, parallel-veined. Flowers fragrant. Fruits normally developed === 2. H. lilioasphodelus
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