''Ageratum houstonianum'', commonly known as flossflower, bluemink, blueweed, pussy foot or Mexican paintbrush, is a cool-season

annual plant An annual plant is a plant that completes its life cycle, from germination to the production of seeds, within one growing season, and then dies. The length of growing seasons and period in which they take place vary according to geographical ...

often grown as bedding in gardens.

Description

This

herbaceous Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and nearly all annuals and biennials. Definitions of "herb" and "herbaceous" The fourth edition of t ...

annual or dwarf shrub grows to high, with ovate to triangular leaves long, and blue flowerheads (sometimes white, pink, or purple). The flower heads are borne in dense

corymbs Corymb is a botanical term for an inflorescence with the flowers growing in such a fashion that the outermost are borne on longer pedicels than the inner, bringing all flowers up to a common level. A corymb has a flattish top with a superficial re ...

. The ray flowers are threadlike and fluff-haired, leading to the common name. The narrow

lanceolate The following is a list of terms which are used to describe leaf morphology in the description and taxonomy of plants. Leaves may be simple (a single leaf blade or lamina) or compound (with several leaflets). The edge of the leaf may be regular o ...

bracts are pointed, denticulate only at the top and glandular hairy. The flowering period is from May to November in the northern hemisphere. The plant attracts butterflies. Bluemink1

Range

The plant is

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 ...

Central America Central America ( es, América Central or ) is a subregion of the Americas. Its boundaries are defined as bordering the United States to the north, Colombia to the south, the Caribbean Sea to the east, and the Pacific Ocean to the west. ...

in Guatemala and Belize, and adjacent parts of Mexico, but has become an

invasive weed An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...

in other areas. It was also naturalized in large parts of the tropics and in the

southern United States The Southern United States (sometimes Dixie, also referred to as the Southern States, the American South, the Southland, or simply the South) is a geographic and cultural region of the United States of America. It is between the Atlantic Ocean ...

. Their habitat is

pasture Pasture (from the Latin ''pastus'', past participle of ''pascere'', "to feed") is land used for grazing. Pasture lands in the narrow sense are enclosed tracts of farmland, grazed by domesticated livestock, such as horses, cattle, sheep, or swine ...

s, moist forest clearings and bushes up to altitudes of . Today, it is widely used as an

ornamental plant Ornamental plants or garden plants are plants that are primarily grown for their beauty but also for qualities such as scent or how they shape physical space. Many flowering plants and garden varieties tend to be specially bred cultivars that i ...

for summer borders and balcony boxes, high varieties also as cut flowers. The species is cultivated once a year, having numerous varieties whose crowns may be dark blue, purple, pink and white. Preferring cool soils and exposure in full sun, high varieties reach stature heights up to .

Chemistry

''Ageratum'' has evolved a unique method of protecting itself from insects: it produces a methoprene-like compound which interferes with the normal function of the

corpus allatum In insect physiology and anatomy, the corpus allatum (plural: corpora allata) is an endocrine gland that generates juvenile hormone; as such, it plays a crucial role in metamorphosis. Surgical removal of the corpora allata (an allatectomy) can caus ...

, the organ responsible for secreting juvenile hormone during insect growth and development. This chemical triggers the next molting cycle to prematurely develop adult structures, and can render most insects sterile if ingested in large enough quantities.

Toxicity

''Ageratum houstonianum'' is toxic to grazing animals, causing liver lesions. It contains pyrrolizidine alkaloids.

Weed risk

''Ageratum houstonianum'' is prone to becoming a rampant environmental weed when grown outside of its natural range. It has become an invasive weed in the United States, Australia,

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

, China, Japan, New Zealand, and the

Philippines The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...

Varieties

*''Ageratum houstonianum'' var. ''angustatum'' B.L. Rob. *''Ageratum houstonianum'' f. ''isochroum'' *''Ageratum houstonianum'' f. ''luteum'' *''Ageratum houstonianum'' var. ''muticescens'' *''Ageratum houstonianum'' f. ''niveum'' *''Ageratum houstonianum'' f. ''normale'' *''Ageratum houstonianum'' var. ''typicum'' *''Ageratum houstonianum'' f. ''versicolor'' The

cultivars A cultivar is a type of Horticulture, cultivated plant that people have selected for desired phenotypic trait, traits and when Plant propagation, propagated retain those traits. Methods used to propagate cultivars include: division, root and st ...

'Blue Danube' and 'Blue Horizon' have gained the

Royal Horticultural Society The Royal Horticultural Society (RHS), founded in 1804 as the Horticultural Society of London, is the UK's leading gardening charity. The RHS promotes horticulture through its five gardens at Wisley (Surrey), Hyde Hall (Essex), Harlow Carr (Nort ...

Award of Garden Merit The Award of Garden Merit (AGM) is a long-established annual award for plants by the British Royal Horticultural Society (RHS). It is based on assessment of the plants' performance under UK growing conditions. History The Award of Garden Merit ...

References

External links

* * {{Taxonbar, from=Q280807 houstonianum Annual plants Flora of Central America Flora of Mexico Garden plants of North America Garden plants of Central America Taxa named by Philip Miller