Daphne (plant)

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Daphne Template:IPAc-en (Template:Langx, "laurel") is a genus of between 70 and 95 species of deciduous and evergreen shrubs in the family Thymelaeaceae, native to Asia, Europe and north Africa. They are noted for their scented flowers and often brightly coloured berries. Two species are used to make paper. Many species are grown in gardens as ornamental plants; the smaller species are often used in rock gardens. All parts of daphnes are poisonous for humans, especially the berries, though birds eat these freely to disperse the seeds.

Description

Daphne species are shrubs, with upright or prostrate stems. Upright species may grow to Template:Cvt, with D. gnidium reported to 2 m,<ref name="Ramos"/> and D. bholua to 4 m.<ref name="RHSD">Template:Cite book</ref> Their leaves are undivided, mostly arranged spirally or alternately (although opposite in D. genkwa), and have short petioles (stalks). The leaves tend to be clustered towards the end of the stems and are of different shapes, although always longer than wide. The leaf surface may be smooth (glabrous) or hairy.<ref name=AGSEncyc/><ref name=FoC/><ref name=FNA/>

Many species flower in late winter or very early spring. The flowers are grouped into clusters (inflorescences), either in the leaf axils towards the end of the stems or forming terminal heads. The inflorescences lack bracts. The individual flowers completely lack petals, and are formed by four (rarely five) petaloid sepals, tubular at the base with free lobes at the apex. They range in colour from white, greenish yellow or yellow to bright pink and purple. Most of the evergreen species have greenish flowers, while the deciduous species tend to have pink flowers. There are twice the number of stamens as sepals, usually eight, arranged in two series. Stamens either have short filaments or lack filaments altogether and are usually held inside the sepal tube. The style is short or absent, and the stigma is head-shaped (capitate).<ref name=AGSEncyc/><ref name=FoC/><ref name=FNA/>

The ovary has a single chamber (locule). The fruit is one-seeded, and is either a fleshy berry, or a dry and leathery drupe.<ref name=FNA/> When ripe the fruit is usually red or yellow, sometimes black.<ref name=AGSEncyc/><ref name=FoC/>

Taxonomy

The genus Daphne was first described by Carl Linnaeus in 1753 in Species Plantarum.<ref name=IPNI_30024583-2/> Linnaeus included ten species, including Daphne mezereum, Daphne laureola and Daphne cneorum.<ref name=Linn53/> Some of his species are now placed in other related genera (e.g. Linnaeus's Daphne thymelaea is now Thymelaea sanamunda).<ref name="TPL_kew-2518411">Template:Citation</ref> The type species of the genus is Daphne laureola.<ref name="f567">Template:Cite web</ref> The number of species in the genus varies considerably between different authorities. The Flora of China states there are about 95 species, 41 of which are endemic to China, and the Euro+Med Plantbase accepts 21 species in the Western Palaearctic region.<ref name="E+M">Template:Cite web</ref> Some of these species were reduced to subspecies or varieties by Josef Halda in a series of papers from 1997 onwards,<ref name=Hald97/> culminating in a monograph on the genus.Template:Sfnp Version 1.1 of The Plant List accepts 83 species.<ref name=TPL_Daphne/>

Phylogeny and generic limits

A 2002 study based on chloroplast DNA placed Daphne in a group of related genera; however there was only one species representing each genus.<ref name=BankFayChas02/>

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A study published in 2009 included an extra species of Wikstroemia and suggested that this genus was paraphyletic with respect to Stellera, but otherwise agreed with the cladogram above.<ref name=BeauEdwaMannMaur09/> The distinction between Wikstroemia and Daphne is difficult to make; Halda included Wikstroemia within Daphne.<ref name=FoC/> The cladogram shown above suggests that other genera would need to be included as well to make Daphne monophyletic.

Two further studies in 2022 and 2023,<ref name="Lee">Template:Cite journal</ref><ref name="Ramos">Template:Cite journal</ref> revealed that Wikstroemia and Daphne formed two closely related but distinct groups, though some species (D. genkwa,<ref name="Lee"/> D. angustiloba, D. aurantiaca, D. holosericea<ref name="Ramos"/>) would need to be transferred from Daphne to Wikstroemia (and possibly others in the reverse direction<ref name="Lee"/>) to give reciprocally monophyletic genera; and additionally, that one species (Daphne championii) should be transferred to another genus, with its closest relative among the species analysed being Edgeworthia chrysantha.<ref name="Lee"/> The necessary formal new combinations were however not made in either paper.

Species

Template:As of, Plants of the World Online accepted the following species:<ref name=POWO_30024583-2>Template:Citation</ref> Template:Div col

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Hybrids

Hybrids accepted by Plants of the World Online are:<ref name=POWO_30024583-2/> Template:Div col

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Numerous artificial hybrids are cultivated as ornamental plants. These include:

Distribution

Daphne is a Eurasian genus, being native to central and southern Europe and Asia,<ref name=FNA/> from Britain<ref name=Stac10/> to Japan.<ref name=Ohwi65/> Some species are also found in north Africa. A number of species have been introduced into other areas for cultivation, with two, D. mezereum and D. laureola, having become naturalised in North America.<ref name=FNA/>

Uses

Two species, Daphne bholua and Daphne papyracea, both called lokta, are harvested in Nepal and Bhutan for paper production.<ref name=ansab/>

Many species are cultivated as ornamental shrubs in gardens.<ref name=PhilRix89>Template:Citation, pp. 36–39</ref> The smaller species are used as rock garden plants or, in the case of those more difficult to grow, as plants for the alpine house. It is recommended that they are grown in well drained but moisture-retentive soil, avoiding strongly acid conditions. Most species prefer a sunny position, although some are woodland plants (e.g. D. mezereum and D. pontica). Propagation is by seed, cuttings or layering.<ref name=AGSEncyc/>

Award of garden merit

The following species, hybrids and cultivars are recipients of the Royal Horticultural Society's Award of Garden Merit: Template:Div col

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Toxicity

All parts of daphnes are toxic, the berries being particularly so. One active compound is daphnin, a glycoside, combining glucose with daphnetin. Some species have been shown to contain a further toxin, mezerein. Symptoms of ingestion include burning sensations and lesions of the mouth and upper digestive tract, gastroenteritis and diarrhoea, and in severe cases, damage to the kidneys (nephritis), irregular heart rhythm, and coma.<ref name=Lewi98/><ref name=Wink09/>

Allergenicity

Daphnes have an OPALS allergy scale rating of 5 out of 10, indicating moderate potential to cause allergic reactions, exacerbated by over-use of the same plant throughout a garden.<ref name = "Ogren">Template:Cite book</ref> The sap and berry juice can cause dermatitis and the scent may affect the odor-sensitive.<ref name="Ogren"/>

References

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Bibliography

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