Significations et usages de agapanthus

Agapanthus
Agapanthus flower and leaves
Scientific classification
Kingdom:	Plantae
clade:	Angiosperms
clade:	Monocots
Order:	Asparagales
Family:	Amaryllidaceae
Subfamily:	Agapanthoideae
Genus:	Agapanthus L'Hér.
Type species
Agapanthus africanus T.A. Durand and Hans Schinz
Species
6-10 species (See text)

Agapanthus ( /ˌæɡəˈpænθəs/)^[1] is the only genus in the subfamily Agapanthoideae of the flowering plant family Amaryllidaceae.^[2] The family is in the monocot order Asparagales.

Agapanthus is commonly known as "Lily of the Nile" ('African lily' in the UK); but it is not a lily and all of the species are native to South Africa, from the Cape of Good Hope to the Limpopo River.^[3]

Species boundaries are not clear in the genus, and in spite of having been intensively studied, the number of species recognized by different authorities varies from 6 to 10. The type species for the genus is Agapanthus africanus.^[4] A great many hybrids and cultivars have been produced and they are cultivated throughout warm areas of the world. ^[5] Most of these were described in a book published in 2004. ^[6]

  Species

Zonneveld & Duncan (2003) divided Agapanthus into six species (A. africanus, A. campanulatus, A. caulescens, A. coddii, A. inapertus, A. praecox). ^[7] Four additional taxa were recognised by Leighton (1965) as species (A. comptonii, A. dyeri, A. nutans, A. walshii), ^[8] but were given subspecific rank by Zonneveld & Duncan. All species recognized by Leighton or by Zonneveld and Duncan are listed below. A. orientalis is also listed.

• Agapanthus africanus (syn. A. umbellatus; African Lily or African Tulip)
• Agapanthus campanulatus (African bluebell, African Blue lily or Bell Agapanthus)
• Agapanthus caulescens
• Agapanthus coddii (Codd's Agapanthus or Blue Lily)
• Agapanthus comptonii
• Agapanthus dyeri
• Agapanthus inapertus (Drakensberg Agapanthus or Drooping Agapanthus)
• Agapanthus nutans
• Agapanthus orientalis
• Agapanthus praecox (Common Agapanthus, Blue Lily, African Lily, or Lily of the Nile)
• Agapanthus walshii

  Description

Agapanthus is a genus of herbaceous perennials that mostly bloom in summer. The leaves are basal and curved, linear, and up to 60 cm (24 in) long. They are arranged in two rows.

The inflorescence is a pseudo-umbel subtended by two large bracts at the apex of a long, erect scape, up to 2 m (6.6 ft) tall. They have funnel-shaped flowers, in hues of blue to purple, shading to white. Some hybrids and cultivars have colors not found in wild plants. The ovary is superior. The style is hollow. Agapanthus does not have the distinctive chemistry of Alliaceae.

  Relationships

Four valid botanical names have Agapanthus as their basionym.^[9]

In 1985, Dahlgren, Clifford, and Yeo placed Agapanthus in Alliaceae, close to Tulbaghia.^[10] Their version of Alliaceae differed from any that are recognized today in that it included Agapanthus and in that it included several genera that would later be transferred to Themidaceae.

In 1996, in a phylogenetic analysis of DNA sequences of the gene rbcL, Themidaceae was resurrected and Agapanthus was removed from Alliaceae.^[11] The authors found Agapanthus to be sister to Amaryllidaceae and transferred it to that family. This was not accepted by the Angiosperm Phylogeny Group when they published the APG system in 1998, because the clade consisting of Agapanthus and Amaryllidaceae had only 63% bootstrap support. The APG system recognized the families Agapanthaceae, Alliaceae, and Amaryllidaceae. Agapanthaceae consisted of Agapanthus only, and Dahlgren's idea that it is close to Tulbaghia was rejected. The APG circumscriptions of the latter two families would eventually become known as Alliaceae sensu stricto, and Amaryllidaceae sensu stricto.

When the APG II system was published in 2003, it offered the option of combining Agapanthaceae, Alliaceae sensu stricto, and Amaryllidaceae sensu stricto to form a larger family, Alliaceae sensu lato. When the name Amaryllidaceae was conserved by the ICBN for this larger family, its name was changed from Alliaceae to Amaryllidaceae, but its circumscription remained the same. When APG II was replaced by APG III in 2009, Agapanthaceae was no longer accepted, but was treated as subfamily Agapanthoideae of the larger version of Amaryllidaceae.^[12] Also in 2009, Armen Takhtajan recognized the three smaller families allowed by APG II, instead of combining them as in APG III.^[13]

Molecular phylogenetic analysis of DNA sequences has shown that Agapanthus is sister to a clade consisting of subfamilies Allioideae and Amaryllidoideae of the family Amaryllidaceae (sensu APG III).^[14] These two subfamilies are equivalent to the families Alliaceae sensu stricto, and Amaryllidaceae sensu stricto, respectively.

  Cultivation and uses

  An agapanthus beginning to bloom

  An agapanthus in pre-bloom stage

Agapanthus africanus can be grown within USDA plant hardiness zones 9 to 11. In lower-numbered zones, the bulbs should be placed deeper in the soil and mulched well in the fall. Agapanthus can be propagated by dividing the bulbs or by seeds. The seeds of most varieties are fertile.

Several hundred cultivars and hybrids are cultivated as garden and landscape plants. Several are winter-hardy to USDA Zone 7. Two cultivars have gained the Royal Horticultural Society's Award of Garden Merit, A. campanulatus subsp. patens^[15], and 'Loch Hope'.^[16]

In some regions, one or more species of Agapanthus are invasive plant species. In New Zealand Agapanthus praecox is classed as an "environmental weed"^[17] and calls to have it added to the National Pest Plant Accord have encountered opposition from gardeners.

  References

  External links

• Agapanthus At:Index Nominum Genericorum At:

References At:

NMNH Department of Botany

• Agapanthus At: Alphabetical Listing by Genera of Validly Published Suprageneric Names At: Home page of James L. Reveal and C. Rose Broome
• Original diagnosis of the genus by L'Héritier online at Project Gutenberg
• Hoyland Plant Centre- UK National Collection Holders- Agapanthus
• PlantZAfrica: Agapanthus africanus