''Pilosella officinarum'' (

synonym A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...

''Hieracium pilosella''), known as mouse-ear hawkweed, is a yellow-flowered species of flowering plant in the daisy family Compositae (=

Asteraceae Asteraceae () is a large family (biology), family of flowering plants that consists of over 32,000 known species in over 1,900 genera within the Order (biology), order Asterales. The number of species in Asteraceae is rivaled only by the Orchi ...

), native to Europe and northern Asia. It produces single, lemon-coloured

inflorescence In botany, an inflorescence is a group or cluster of flowers arranged on a plant's Plant stem, stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a mai ...

s. Like most

hawkweed ''Hieracium'' (), known by the common name hawkweed and classically as (from ancient Greek ἱέραξ, 'hawk'), is a genus of flowering plant in the family Asteraceae, and closely related to dandelion (''Taraxacum''), chicory (''Cichorium''), ...

species, it is highly variable and is a member of a species complex of several dozens of subspecies and hundreds of varieties and forms. It is an

allelopathic Allelopathy is a biological phenomenon by which an organism produces one or more biochemicals that influence the germination, growth, survival, and reproduction of other organisms. These biochemicals are known as allelochemicals and can have ben ...

plant.

Description

It is a

hispid Trichomes (; ) are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a plant ...

(hairy)

perennial plant In horticulture, the term perennial (''wikt:per-#Prefix, per-'' + ''wikt:-ennial#Suffix, -ennial'', "through the year") is used to differentiate a plant from shorter-lived annual plant, annuals and biennial plant, biennials. It has thus been d ...

, with a basal rosette of

leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...

. The whole plant, with the exception of the flower parts, is covered in glandular hairs, usually whitish, sometimes reddish on the stem. The rosette leaves are entire, acute to blunt, and range from long and broad. Their underside is

tomentose Trichomes (; ) are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a plant ...

(covered with hair). The flowering stem ( scape) is generally between tall, and sprouts from the centre of the basal rosette. The

flower Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants ( angiosperms). Typically, they are structured in four circular levels, called whorls, around the end of a stalk. These whorls include: calyx, m ...

heads are borne singly on the scape and are a pale lemon-yellow colour, with the outermost ligules having a reddish underside. It flowers from May until August and the flowers are visited by various groups of insects, especially flies. The plant favours dry, sunny areas. It grows well on sandy and similarly less fertile ground types. It produces

stolon In biology, a stolon ( from Latin ''wikt:stolo, stolō'', genitive ''stolōnis'' – "branch"), also known as a runner, is a horizontal connection between parts of an organism. It may be part of the organism, or of its skeleton. Typically, animal ...

s which generate a new rosette at their extremity, each rosette has the possibility of developing into a new clone forming dense mats in open space. It also propagates by

seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...

Ecology

It is a known

plant, whose roots secrete several substances inhibiting root growth, including its own. It can be controlled through rotation with

clover Clovers, also called trefoils, are plants of the genus ''Trifolium'' (), consisting of about 300 species of flowering plants in the legume family Fabaceae originating in Europe. The genus has a cosmopolitan distribution with the highest diversit ...

and grasses where possible. Recent research claims that ''Pilosella officinarum'' exhibits an

atavism In biology, an atavism is a modification of a biological traits structure or behavior whereby an ancestral genetic trait reappears after having been lost through evolutionary change in previous generations. Atavisms can occur in several ways, ...

by the reemergence of

sexual reproduction Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote tha ...

. The plant has been found as an

invasive species An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...

in ''

Sphagnum ''Sphagnum'' is a genus of approximately 380 accepted species of mosses, commonly known as sphagnum moss, also bog moss and quacker moss (although that term is also sometimes used for peat). Accumulations of ''Sphagnum'' can store water, since ...

'' peatlands disturbed by peat extraction in southern

Patagonia Patagonia () is a geographical region that includes parts of Argentina and Chile at the southern end of South America. The region includes the southern section of the Andes mountain chain with lakes, fjords, temperate rainforests, and glaciers ...

Similar species

Shetland mouse-ear hawkweed (''Pilosella flagellaris'' subsp. ''bicapitata'') is similar, but has two flowers per leaf stalk. It is found in the

Shetland Islands Shetland (until 1975 spelled Zetland), also called the Shetland Islands, is an archipelago in Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the Uni ...

only, on rocky coastal

grassland A grassland is an area where the vegetation is dominance (ecology), dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes such as clover, and other Herbaceo ...

. It flowers from May to August.

Cultivation and uses

Mouse-ear hawkweed has become a common introduced

in North America (where it is found in southern Canada and both north-east and north-west United States), and New Zealand. It is a level C noxious weed in the United States (with higher levels in the states of

Washington Washington most commonly refers to: * George Washington (1732–1799), the first president of the United States * Washington (state), a state in the Pacific Northwest of the United States * Washington, D.C., the capital of the United States ** A ...

and

Oregon Oregon ( , ) is a U.S. state, state in the Pacific Northwest region of the United States. It is a part of the Western U.S., with the Columbia River delineating much of Oregon's northern boundary with Washington (state), Washington, while t ...

), and a weed in

Quebec Quebec is Canada's List of Canadian provinces and territories by area, largest province by area. Located in Central Canada, the province shares borders with the provinces of Ontario to the west, Newfoundland and Labrador to the northeast, ...

. It does not have special designations in other locations in Canada. It is known to be strongly invasive in New Zealand's tussock fields, where there are no native species of hawkweed, and

biological control Biological control or biocontrol is a method of controlling pests, whether pest animals such as insects and mites, weeds, or pathogens affecting animals or plants by using other organisms. It relies on predation, parasitism, herbivory, or o ...

measures are being undertaken to control it and other similar species. In Victoria and NSW, Australia, Hawkweed Sp. are declared as State Prohibited Weeds and are controlled under The Bio Security Act 2015. Currently there are several eradication programs operating (often employing volunteers) to locate, prevent the spread of and eradicate any Pilosella (Hieracium) sp. plants.

Joseph Pitton de Tournefort Joseph Pitton de Tournefort (5 June 165628 December 1708) was a French botanist, notable as the first to make a clear definition of the concept of genus for plants. Botanist Charles Plumier was his pupil and accompanied him on his voyages. Li ...

mentions that blades covered in this plant's juices were believed to cut through stone as easily as through wood.Hieracium pilosella
in the online Flore Laurentienne

Phytochemistry

The mouse-ear hawkweed contains

umbelliferone Umbelliferone, also known as 7-hydroxycoumarin, hydrangine, skimmetine, and ''beta''-umbelliferone, is a natural product of the coumarin family. It absorbs ultraviolet light strongly at several wavelengths. There are some indications that this c ...

, a compound similar to

coumarin Coumarin () or 2''H''-chromen-2-one is an aromatic organic chemical compound with formula . Its molecule can be described as a benzene molecule with two adjacent hydrogen atoms replaced by an unsaturated lactone ring , forming a second six-me ...

. The plant produces

triterpenoid Triterpenes are a class of terpenes composed of six isoprene units with the molecular formula C30H48; they may also be thought of as consisting of three terpene units. Animals, plants and fungi all produce triterpenes, including squalene, the pre ...

s, mainly taraxasterol, but also the 4,4-dimethyl

phytosterol Phytosterols are phytosteroids, similar to cholesterol, that serve as structural components of biological membranes of plants. They encompass plant sterols and stanol ester, stanols. More than 250 sterols and related compounds have been identified ...

s alpha- and beta-

amyrin The amyrins are three closely related natural chemical compounds of the triterpene class. They are designated α-amyrin (ursane skeleton), β-amyrin (oleanane skeleton), and δ-amyrin. Each is a pentacyclic triterpenol with the chemical formula ...

taraxerol Taraxerol is a naturally-occurring pentacyclic Triterpene, triterpenoid. It exists in various higher plants, including ''Taraxacum officinale'' (Asteraceae), ''Alnus glutinosa'' (Betulaceae), Litsea, ''Litsea dealbata'' (Lauraceae), Skimmia, ''Ski ...

, and fern-7en-3beta-ol. It has been used in folk medicine, and recreationally as a

cannabis ''Cannabis'' () is a genus of flowering plants in the family Cannabaceae that is widely accepted as being indigenous to and originating from the continent of Asia. However, the number of species is disputed, with as many as three species be ...

substitute.

Image gallery

Hieracium pilosella Ł2.jpg P3038214 Pilosella officinarum - Mouse-ear Hawkweed.jpg

References

External links

* {{Taxonbar, from1=Q15593797, from2=Q931460 officinarum Medicinal plants of Asia Medicinal plants of Europe Plants described in 1753 Taxa named by Carl Linnaeus