''Ageratum'' () (whiteweed in the USA) is a genus of 40 to 60 tropical and warm temperate flowering annuals and perennials from the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Asteraceae,

tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide usage of the term in English language, English is in the discipline of anthropology. This definition is contested, in p ...

Eupatorieae. Most species are

native Native may refer to: People * Jus soli, citizenship by right of birth * Indigenous peoples, peoples with a set of specific rights based on their historical ties to a particular territory ** Native Americans (disambiguation) In arts and entert ...

to Central America and Mexico but four are native to the United States. They form tussocks or small hills. They grow to a height of 30 in. The

opposite leaves In botany, phyllotaxis () or phyllotaxy is the arrangement of leaves on a plant stem. Phyllotactic spirals form a distinctive class of patterns in nature. Leaf arrangement The basic arrangements of leaves on a stem are opposite and alterna ...

are cordate or oval, hairy or tomentose. The margins are slightly toothed or serrate. The leaves form compact clusters. The fluffy

flower A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechani ...

s are lavender-blue, pink, lilac, or white; and spread in small compound umbels. They give small, dry fruits.

Cultivation

Ageratums are grown for their flowers, especially '' A. houstonianum''. Most common ageratums, "Hawaii" for example, are a short 6-8 inches when full grown. Tall ageratum are also available in seed catalogues. They are about 18 inches in height with blue flowers. There is also a medium height snowcapped variety, white top on blue flowers. The blues are most popular and common, but colors also include violet, pink and white. Their size and color makes ageratums good candidates for rock gardens,

bedding Bedding, also known as bedclothes or bed linen, is the materials laid above the mattress of a bed for hygiene, warmth, protection of the mattress, and decorative effect. Bedding is the removable and washable portion of a human sleeping environm ...

, and containers. They grow well in sun or partial shade, from early summer to first frost. They are quite easy to grow, producing a profusion of fluffy flowers all season long.

Toxicity

Several species of ''Ageratum'' are

toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subst ...

, containing

pyrrolizidine alkaloids Pyrrolizidine alkaloids (PAs), sometimes referred to as necine bases, are a group of naturally occurring alkaloids based on the structure of pyrrolizidine. Pyrrolizidine alkaloids are produced by plants as a defense mechanism against insect he ...

. ''Ageratum houstonianum'' and ''

Ageratum conyzoides ''Ageratum conyzoides'' (billygoat-weed, chick weed, goatweed, whiteweed, mentrasto) is native to Tropical America, especially Brazil, and is an invasive weed in many other regions. It is an herb that is 0.5–1 m. high, with ovate leaves 2–6& ...

'' cause

liver The liver is a major Organ (anatomy), organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of proteins and biochemicals necessary for ...

lesions A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. ''Lesion'' is derived from the Latin "injury". Lesions may occur in plants as well as animals. Types There is no designated classifi ...

and are

tumorigenic Carcinogenesis, also called oncogenesis or tumorigenesis, is the formation of a cancer, whereby normal cells are transformed into cancer cells. The process is characterized by changes at the cellular, genetic, and epigenetic levels and abno ...

Weed risk

''Ageratum conyzoides'' and ''Ageratum houstonianum'' are prone to becoming rampant environmental

weed A weed is a plant considered undesirable in a particular situation, "a plant in the wrong place", or a plant growing where it is not wanted.Harlan, J. R., & deWet, J. M. (1965). Some thoughts about weeds. ''Economic botany'', ''19''(1), 16-24. ...

s when grown outside of their natural range.

Species

, ''Plants of the World online'' has 40 accepted species: Selected synonyms include: * '' Ageratum altissimum'' — synonym of ''

Ageratina altissima ''Ageratina altissima'', also known as white snakeroot, richweed, or white sanicle, is a poisonous perennial herb in the family Asteraceae, native to eastern and central North America. An older binomial name for this species is ''Eupatorium rugo ...

'' * '' Ageratum anisochroma'' — synonym of ''

Ageratina anisochroma ''Ageratina'' (snakeroot) is a genus of more than 330 perennials and rounded shrubs in the family Asteraceae. These plants grow mainly in the warmer regions of the Americas and West Indies. Over 150 species are native to Mexico. Some flourish i ...

'' * '' Ageratum isocarphoides'' — synonym of ''

Ageratum echioides ''Ageratum'' () (whiteweed in the USA) is a genus of 40 to 60 tropical and warm temperate flowering annuals and perennials from the family Asteraceae, tribe Eupatorieae. Most species are native to Central America and Mexico but four are native ...

'' * '' Ageratum lavenia'' — synonym of '' Adenostemma lavenia'' * '' Ageratum lucidum'' — synonym of ''

Ageratum corymbosum ''Ageratum'' () (whiteweed in the USA) is a genus of 40 to 60 tropical and warm temperate flowering annuals and perennials from the family Asteraceae, tribe Eupatorieae. Most species are native to Central America and Mexico but four are native ...

'' * '' Ageratum meridanum'' — synonym of '' Ageratum microcarpum'' * '' Ageratum nelsonii'' — synonym of ''

Ageratum elassocarpum ''Ageratum'' () (whiteweed in the USA) is a genus of 40 to 60 tropical and warm temperate flowering annuals and perennials from the family Asteraceae, tribe Eupatorieae. Most species are native to Central America and Mexico but four are native ...

'' * '' Ageratum oliveri'' — synonym of ''

Ageratum oerstedii ''Ageratum'' () (whiteweed in the USA) is a genus of 40 to 60 tropical and warm temperate flowering annuals and perennials from the family Asteraceae, tribe Eupatorieae. Most species are native to Central America and Mexico but four are native ...

'' * '' Ageratum panamense'' — synonym of '' Ageratum riparium'' * ''

Ageratum pohlii ''Ageratum'' () (whiteweed in the USA) is a genus of 40 to 60 tropical and warm temperate flowering annuals and perennials from the family Asteraceae, tribe Eupatorieae. Most species are native to Central America and Mexico but four are native ...

'' — synonym of ''

Teixeiranthus pohlii ''Teixeiranthus'' is a genus of Brazilian plants in the tribe Eupatorieae within the family Asteraceae.D.J.N.Hind & H.E.Robinson. 2007. Tribe Eupatorieae In: ''The Families and Genera of Vascular Plants'' vol.VIII. (Joachim W.Kadereit & Charles J ...

'' * ''

Ageratum radicans ''Ageratum'' () (whiteweed in the USA) is a genus of 40 to 60 tropical and warm temperate flowering annuals and perennials from the family (biology), family Asteraceae, tribe (biology), tribe Eupatorieae. Most species are native plant, native t ...

'' — synonym of '' Ageratum peckii'' * '' Ageratum salicifolium'' — synonym of ''

'' * '' Ageratum stachyofolium'' — synonym of '' Paneroa stachyofolia''

Segregate genera

The genus ''Paneroa'' consists of one species, ''Paneroa stachyofolia'', native to

Oaxaca Oaxaca ( , also , , from nci, Huāxyacac ), officially the Free and Sovereign State of Oaxaca ( es, Estado Libre y Soberano de Oaxaca), is one of the 32 states that compose the political divisions of Mexico, Federative Entities of Mexico. It is ...

, which was first described in ''Ageratum'' but which seems to be more closely related to ''

Conoclinium ''Conoclinium'', the mistflowers, is a genus of four species of herbaceous perennial flowering plants, native to North America. They are tall, and have blue to purple or violet flowers (occasionally white). The plants of this genus have sometim ...

'' and '' Fleischmannia''.

References

{{Taxonbar, from=Q132653 Asteraceae genera Taxa named by Carl Linnaeus