Ageratum

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Ageratum
Common liver balm (Ageratum houstonianum) as a bedding plant

Common liver balm ( Ageratum houstonianum ) as a bedding plant

Systematics
Order : Astern-like (Asterales)
Family : Daisy family (Asteraceae)
Subfamily : Asteroideae
Tribe : Eupatorieae
Sub tribus : Ageratinae
Genre : Ageratum
Scientific name
Ageratum
L.

Ageratum is a genus of plants in the sunflower family (Asteraceae). This genus is neotropically distributedwith around 40 species. The best known type is the common liver balm ( Ageratum houstonianum ), which is used with some varieties as an ornamental plant in parks, gardens and window boxes.

description

Illustration of Ageratum conyzoides

Appearance and leaves

The Ageratum species grow as annual to perennial herbaceous plants or subshrubs and usually reach heights of 20 to 120 centimeters. The upright to often lying sparse to dense branched stems sometimes form at the bottom node ( Nodien ) roots.

Most opposite, sometimes (the top) one another arranged on the stem leaves are usually pedunculated. The simple leaf blade is elliptical, egg-shaped or lanceolate to delta-shaped. The leaf margin is smooth to toothed. Only a leaf vein can be seen on the leaf surfaces and they are glabrous to more or less soft, fluffy or stiff-bristly hairy and sometimes dotted with glands.

Detail of an inflorescence of the common liver balsam ( Ageratum houstonianum ) with some flower heads

Inflorescences, flowers and fruits

The cup-shaped partial inflorescences are in dense to open, more or less zymous , umbrella-clustered or almost dold-like total inflorescences. The flower heads are disc-shaped. In an involucre, usually bell-shaped at a height of 3 to 6 millimeters, there are 30 to 40 more or less identically shaped, durable, more or less herbaceous, lanceolate bracts (involucre leaves) in two or three rows , which more or less overlap and clearly harden are as well as often have a dry-skinned edge. The bracts are shorter than the flowers. The conical base of the inflorescence (receptacle) can sometimes have leaves of chaff. There are no ray florets available (daisies).

The 20 to 125 tubular flowers (= disc flowers) are hermaphroditic. The mostly white or blue to lavender-colored petals are fused into a tubular to funnel-shaped corolla tube, which widens more or less wide bell-shaped at the top and ends with five crown teeth. The petals are papillous and hairy on the outside and papilliose on the inside. The crown teeth are about as long as they are wide. The anthers are blunt at their base and have appendages at the top. The two stylus branches protruding from the corolla tube are linear to club-shaped and mostly strong and densely papillary .

The prismatic achenes , sometimes narrowed at their base, are four to five-ribbed with a bald or sometimes sparsely stiff-bristle hairy surface. The pappus consists of five or six free scales or scales that are crown-shaped at their base; sometimes a pappus is missing.

Chromosome number

The basic chromosome number is x = 10.

distribution

The genus Ageratum has a neotropical distribution. Species occur from the USA to Mexico to Central America and South America . Two species are cultivated and are neophytes in many areas of the world .

Opposite, simple leaves and inflorescence of Ageratum conyzoides
Habit and inflorescences of Ageratum corymbosum

Systematics

Ageratum peckii , sub-endemic in Belize

The genus Ageratum was established by Carl von Linné in 1753 . Ageratum conyzoides L. was introduced as a lectotype species in 1925 by Britton and P. Wilson in Scient. Surv. Porto Rico , 6, p. 286 set. The genus Ageratum belongs to the subtribe Ageratinae from the tribe Eupatorieae in the subfamily Asteroideae within the family Asteraceae .

There are about 40 species in the genus Ageratum :

The species Ageratum stachyofolium B.L.Rob. was spun off into the monotypical genus Paneroa in 2008 : Paneroa stachyofolia (BLRob.) EESchill. is native to the Mexican state of Oaxaca .

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Individual evidence

  1. ↑ a b c d e f g h Guy L. Nesom: Ageratum , p. 481 - same text online and printed work : Tribus Eupatorieae , In: Flora of North America Editorial Committee (ed.): Flora of North America North of Mexico , Volume 21 - Magnoliophyta: Asteridae (in part): Asteraceae, part 3 - Oxford University Press, New York and Oxford 2006, ISBN 0-19-530565-5 .
  2. ↑ a b c d e f g Yilin Chen, Takayuki Kawahara & DJ Nicholas Hind: Tribus Eupatorieae : Ageratum , p. 883 - same text online as the printed work , In: Wu Zheng-Yi, Peter H. Raven & Deyuan Hong (editor) : Flora of China , Volume 20-21 - Asteraceae , Science Press and Missouri Botanical Garden Press, Beijing and St. Louis, November 12, 2011. ISBN 978-1-935641-07-0
  3. ↑ a b c d e f g h MF Porteners: Ageratum in the New South Wales Flora Online .
  4. ↑ Species Plantarum , 2, pp. 839-840
  5. ^ A b Ageratum in the Germplasm Resources Information Network (GRIN), USDA , ARS , National Genetic Resources Program. National Germplasm Resources Laboratory, Beltsville, Maryland.
  6. ↑ Assessment of recognized names in the Global Compositae Checklist .
  7. ↑ Assessment of recognized names at ThePlantlist .
  8. ↑ ageratum iltisii in the Red List of Threatened Species of the IUCN 2011. Posted by: R. Montúfar & N. Pitman, 2003. Accessed January 9, 2012 Design.
  9. ↑ Edward E. Schilling: Paneroa, A New Genus of Eupatorieae (Asteraceae) from Mexico , Novon , Volume 18, Issue 4, 2008, p 520. doi : 10.3417 / 2007173

Web links

Commons : Ageratum  - collection of images, videos and audio files