''Hieracium'' (), known by the common name hawkweed and classically as (from

ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

ἱέραξ, '

hawk Hawks are birds of prey of the family Accipitridae. They are very widely distributed and are found on all continents, except Antarctica. The subfamily Accipitrinae includes goshawks, sparrowhawks, sharp-shinned hawks, and others. This ...

'), is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

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 ...

, and closely related to dandelion (''

Taraxacum ''Taraxacum'' () is a genus of flowering plants in the family Asteraceae, which consists of species commonly known as dandelions. The scientific and hobby study of the genus is known as taraxacology. The genus has a near-cosmopolitan distribu ...

''), chicory (''

Cichorium ''Cichorium'' is a genus of plants in the tribe Cichorieae within the family Asteraceae. The genus includes two cultivated species commonly known as chicory or endive, plus several wild species.Lactuca'') and sow thistle ('' Sonchus''), which are part of the

tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide use of the term in English is in the discipline of anthropology. The definition is contested, in part due to conflict ...

Cichorieae The Cichorieae (also called Lactuceae) are a tribe in the plant family Asteraceae that includes 93 genera, more than 1,600 sexually reproductive species and more than 7,000 apomictic species. They are found primarily in temperate regions of the E ...

. Hawkweeds, with their 10,000+ recorded species and subspecies, do their part to make Asteraceae the second largest family of flowering plants. Some botanists group all these species or subspecies into approximately 800 accepted species, while others prefer to accept several thousand species. Since most hawkweeds reproduce exclusively asexually by means of

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 ...

s that are genetically identical to their mother plant (

apomixis In botany, apomixis is asexual development of seed or embryo without fertilization. However, other definitions include replacement of the seed by a plantlet or replacement of the flower by bulbils. Apomictically produced offspring are geneti ...

or agamospermy), clones or populations that consist of genetically identical plants are formed and some botanists (especially in UK, Scandinavia and Russia) prefer to accept these clones as good species (arguing that it is impossible to know how these clones are interrelated) whereas others (mainly in Central Europe and USA) try to group them into a few hundred more broadly defined species. What is here treated as the single genus ''Hieracium'' is now treated by most European experts as two different genera, ''Hieracium'' and '' Pilosella'', with species such as ''Hieracium pilosella'', ''Hieracium floribundum'' and ''Hieracium aurantiacum'' referred to the latter genus. Many members of the genus ''Pilosella'' reproduce both by

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 (runners like those of strawberries) and by seeds, whereas true ''Hieracium'' species reproduce only by seeds. In ''Pilosella'', many individual plants are capable of forming both normal sexual and asexual (apomictic) seeds, whereas individual plants of ''Hieracium'' only produce one kind of seeds. Another difference is that all species of ''Pilosella'' have leaves with smooth (entire) margins whereas most species of ''Hieracium'' have distinctly dentate to deeply cut or divided leaves.

Description

Flowers and flower-heads

''Hieracium'' or hawkweeds, like others in the family Asteraceae, mostly have

yellow Yellow is the color between green and orange on the spectrum of light. It is evoked by light with a dominant wavelength of roughly 575585 nm. It is a primary color in subtractive color systems, used in painting or color printing. In t ...

, tightly packed flower-heads of numerous small flowers but, unlike daisies and

sunflower The common sunflower (''Helianthus annuus'') is a species of large annual forb of the daisy family Asteraceae. The common sunflower is harvested for its edible oily seeds, which are often eaten as a snack food. They are also used in the pr ...

s in the same family, they have not two kinds of

floret This glossary of botanical terms is a list of definitions of terms and concepts relevant to botany and plants in general. Terms of plant morphology are included here as well as at the more specific Glossary of plant morphology and Glossary ...

s but only strap-shaped ( spatulate) florets, each one of which is a complete

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 ...

in itself, not lacking stamens, and joined to the stem by leafy

bracts In botany, a bract is a modified or specialized leaf, associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves in size, color, shape or texture. They also loo ...

. As in other members of the tribe

, each ray corolla is tipped by 3 to 5 teeth.

Bracts, stems and leaves

Erect single,

glabrous Glabrousness () is the technical term for a lack of hair, down, setae, trichomes, or other such covering. A glabrous surface may be a natural characteristic of all or part of a plant or animal, or be due to loss because of a physical condition, ...

or hairy stems, sometimes branched away from the point of attachment, sometimes branched throughout. The hairiness of hawkweeds can be very complex: from surfaces with scattered to crowded, tapered, whiplike, straight or curly, smooth to

setae In biology, setae (; seta ; ) are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Depending partly on their form and function, protostome setae may be called macrotrichia, chaetae ...

; " stellate-pubescent" or surfaces with scattered to crowded, dendritically branched (often called, but seldom truly, "stellate") hairs; and " stipitate- glandular" or surfaces with scattered to crowded gland-tipped hairs mostly. Surfaces of stems, leaves, peduncles, and phyllaries may be glabrous or may bear one, two, or all three of the types of hairs mentioned above. Like the other members of the Chicory tribe, hawkweeds contain a milky latex.

Ecology

The large yellow underwing moth (''Noctua pronuba'') feeds on ''Hieracium'' species.

Distribution

''Hieracium'' species are native to

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

Central America Central America is a subregion of North America. Its political boundaries are defined as bordering Mexico to the north, Colombia to the southeast, the Caribbean to the east, and the Pacific Ocean to the southwest. Central America is usually ...

and

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

Species

The classification of ''Hieracium'' into species is notoriously difficult. One reason is the

apomictic In botany, apomixis is asexual reproduction, asexual development of seed or embryo without Fertilisation, fertilization. However, other definitions include replacement of the seed by a plantlet or replacement of the flower by bulbils. Apomictic ...

reproduction (in which plants asexually produce seeds), which tends to produce a lot of minor geographical variation. Over 9000 species names have been published in ''Hieracium'' but some botanists regard many of those as synonyms of larger species.

Europe

*'' Hieracium attenboroughianum'' – Attenborough’s hawkweed *'' Hieracium bakerianum'' *'' Hieracium hethlandiae'' – Cliva Hill hawkweed *'' Hieracium lepidulum'' Stenstr. ex Dahlst. – tussock hawkweed *'' Hieracium lucidum'' Guss. – Sicilian sparviere *'' Hieracium insolitum'' (Zahn) Üksip *'' Hieracium villosum'' Jacq.

North America

The list below is a selection of species that have been accepted by the USDA

Natural Resources Conservation Service Natural Resources Conservation Service (NRCS), formerly known as the Soil Conservation Service (SCS), is an agency of the United States Department of Agriculture (USDA) that provides technical assistance to farmers and other private landowners and ...

and Canada. A more complete list is given in the list of ''Hieracium'' species. *'' Hieracium albertinum'' – houndstongue hawkweed *'' Hieracium albiflorum'' Hook. – white hawkweed *'' Hieracium × alleghaniense'' Britt. (pro sp.) *''

Hieracium argutum ''Hieracium argutum'' is a species of flowering plant in the family Asteraceae known by the common name southern hawkweed. It is Endemism, endemic to California, where it can be found in coastal and inland hills and mountains, often in oak woodl ...

'' Nutt. – southern hawkweed *'' Hieracium × atramentarium'' (Naegeli & Peter) Zahn ex Engl. (pro sp.) *'' Hieracium atratum'' Fries – polar hawkweed *'' Hieracium bolanderi'' Gray – Bolander's hawkweed *'' Hieracium × brachiatum'' Berth. ex DC. *'' Hieracium canadense'' Michx. – Canada hawkweed *'' Hieracium carneum'' Greene – Huachuca hawkweed *'' Hieracium × fassettii'' Lepage *'' Hieracium fendleri'' Schultz-Bip. – yellow hawkweed *'' Hieracium × fernaldii'' Lepage *'' Hieracium × fuscatrum'' Naegeli & Peter (pro sp.) *'' Hieracium glomeratum'' Froel. – queen-devil hawkweed *'' Hieracium gracile'' Hook. – slender hawkweed *'' Hieracium greenei'' Gray – Greene's hawkweed *'' Hieracium greenii'' Porter & Britt. – Maryland hawkweed *'' Hieracium × grohii'' Lepage *'' Hieracium gronovii'' L. – queendevil *'' Hieracium horridum'' Fries – prickly hawkweed *'' Hieracium kalmii'' L. – Kalm's hawkweed *'' Hieracium lachenalii'' K.C. Gmel. – common hawkweed *'' Hieracium laevigatum'' Willd. – smooth hawkweed *'' Hieracium lemmonii'' Gray – Lemmon's hawkweed *'' Hieracium longiberbe'' T.J. Howell – longbeard hawkweed *'' Hieracium longipilum'' Torr. – hairy hawkweed *'' Hieracium maculatum'' Sm. – spotted hawkweed *'' Hieracium marianum'' Willd. – Maryland hawkweed *'' Hieracium megacephalum'' Nash – coastal plain hawkweed *'' Hieracium murorum'' L. – wall hawkweed *'' Hieracium paniculatum'' L. – Allegheny hawkweed *'' Hieracium parryi'' Zahn in H.G.A. Engler – Parry hawkweed *'' Hieracium piloselloides'' Vill. – tall hawkweed *'' Hieracium praealtum'' Vill. ex Gochnat – kingdevil *'' Hieracium pringlei'' Gray – Pringle's hawkweed *'' Hieracium robinsonii'' (Zahn) Fern. – Robinson's hawkweed *'' Hieracium rusbyi'' Greene – Rusby's hawkweed *'' Hieracium sabaudum'' L. – New England hawkweed *'' Hieracium scabrum'' Michx. – rough hawkweed *'' Hieracium schultzii'' Fries – roughstem hawkweed *'' Hieracium scouleri'' Hook. – Scouler's woollyweed *'' Hieracium scribneri'' Small – Scribner's hawkweed *'' Hieracium traillii'' – Maryland hawkweed *'' Hieracium triste'' Willd. ex Spreng. – woolly hawkweed *'' Hieracium umbellatum'' L. – narrowleaf hawkweed *'' Hieracium venosum'' L. – rattlesnakeweed Some species are now placed in the genus '' Pilosella'': *''Hieracium aurantiacum'' L., syn. of ''

Pilosella aurantiaca ''Pilosella aurantiaca'' (fox-and-cubs, orange hawkweed, devil's paintbrush, grim-the-collier) is a perennial plant, perennial flowering plant in the family Asteraceae that is native to alpine regions of Central Europe, central and southern Europ ...

'' – orange hawkweed *''Hieracium caespitosum'' Dumort., syn. of '' Pilosella caespitosa'' – meadow hawkweed *''Hieracium flagellare'' Willd., syn. of '' Pilosella flagellaris'' – whiplash hawkweed *''Hieracium floribundum'' Wimmer & Grab., syn. of '' Pilosella floribunda'' – kingdevil hawkweed *''Hieracium lactucella'' Wallr., syn. of '' Pilosella lactucella'' – European hawkweed *''Hieracium pilosella'' L., syn. of '' Pilosella officinarum'' – mouse-ear hawkweed

Plant pest

All species of the genus ''Hieracium'' are classed as

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 ...

throughout

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

. They are banned from sale, propagation and distribution under the National Pest Plant Accord. ''Hieracium'' is a pasture weed that reduces available feed for livestock and displaces the indigenous plants. It is a particular threat in alpine ecosystems previously dominated by native tussocks, though it will colonise habitats from bare ground, to exotic

pine A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. ''World Flora Online'' accepts 134 species-rank taxa (119 species and 15 nothospecies) of pines as cu ...

forest, to native Southern Beech forest. In the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

, many species of ''Hieracium'' have been introduced and all species present are considered noxious weeds in one or more states. In Australia, hawkweeds are invasive pests in alpine regions, all species of ''Hieracium'' are listed or declared under various State Acts.

References

External links

* * * * * * {{Taxonbar, from=Q16526 Asteraceae genera Taxa named by Carl Linnaeus