Hieracium
Encyclopedia
Hieracium known by its common name Hawkweed and long ago by its classical name hierakion which comes from the ancient Greek hierax, "a hawk
"
is a genus
of the sunflower (Helianthus
) family
Asteraceae
(previously called Compositae) and are closely related to dandelion (Taraxacum
), chicory (Cichorium
), prickly lettuce (Lactuca
) and sow thistle (Sonchus
)
which are part of the tribe
Cichorieae
. Hawkweeds with their 10,000+ recorded species and subspecies
, do their part to make Asteraceae the second largest family of flowers.
Some botanists group all these species or subspecies into approximately 800 accepted species
, whereas others prefer to accept several thousand species. Since most hawkweeds reproduce exclusively asexually by means of seed
s that are genetically identical to their mother plant (apomixis
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 by most European experts now treated 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
s (runners like those of strawberries) and by seeds, whereas true Hieracium species only reproduce 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.
,
tightly packed flower-heads
of numerous small flowers
but unlike daisies
and sunflower
s in the same family, they have not two kinds of florets but only strap-shaped (spatulate) florets, each one of which is a complete flower
in itself, not lacking stamens,
and joined to the stem by leafy bracts. Like other tribe Cichorieae members each ray corolla is tipped by 3 to 5 teeth.
, 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; "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
, Hieraciums contain a milky latex.
,Asia
, Europe
, North America
, Central America
and South America
.
.
A more complete list is given in List of Hieracium species.
throughout New Zealand
. 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 forest, to native Southern Beech
forest.
In the United States
, many species of Hieracium have been introduced and all species present are considered noxious weeds
in one or more states.
Hawk
The term hawk can be used in several ways:* In strict usage in Australia and Africa, to mean any of the species in the subfamily Accipitrinae, which comprises the genera Accipiter, Micronisus, Melierax, Urotriorchis and Megatriorchis. The large and widespread Accipiter genus includes goshawks,...
"
is a genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of the sunflower (Helianthus
Helianthus
Helianthus L. is a genus of plants comprising 52 species in the Asteraceae family, all of which are native to North America, with some species Helianthus L. is a genus of plants comprising 52 species in the Asteraceae family, all of which are native to North America, with some species Helianthus...
) family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Asteraceae
Asteraceae
The Asteraceae or Compositae , is an exceedingly large and widespread family of vascular plants. The group has more than 22,750 currently accepted species, spread across 1620 genera and 12 subfamilies...
(previously called Compositae) and are closely related to dandelion (Taraxacum
Taraxacum
Taraxacum is a large genus of flowering plants in the family Asteraceae. They are native to Eurasia and North America, and two species, T. officinale and T. erythrospermum, are found as weeds worldwide. Both species are edible in their entirety...
), chicory (Cichorium
Cichorium
Cichorium is a genus of flowering plants in the family Asteraceae. The species are commonly known as chicory or endive – there are two cultivated species, and four to six wild species....
), prickly lettuce (Lactuca
Lactuca
Lactuca, commonly known as lettuce, is a genus of flowering plants in the daisy family Asteraceae. The genus includes about 100 species, distributed worldwide, but mainly in temperate Eurasia....
) and sow thistle (Sonchus
Sonchus
Sonchus is a genus of flowering plants in the daisy family Asteraceae. Most of the species are annual herbs, a few are perennial, and some are even woody...
)
which are part of the tribe
Tribe (biology)
In biology, a tribe is a taxonomic rank between family and genus. It is sometimes subdivided into subtribes.Some examples include the tribes: Canini, Acalypheae, Hominini, Bombini, and Antidesmeae.-See also:* Biological classification* Rank...
Cichorieae
Cichorieae
Cichorieae is a tribe of plants in the family Asteraceae that includes 100 genera and more than 1,600 species. They are found primarily in temperate regions of the Eastern Hemisphere....
. Hawkweeds with their 10,000+ recorded species and subspecies
, do their part to make Asteraceae the second largest family of flowers.
Some botanists group all these species or subspecies into approximately 800 accepted species
, whereas others prefer to accept several thousand species. Since most hawkweeds reproduce exclusively asexually by means of seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...
s that are genetically identical to their mother plant (apomixis
Apomixis
In botany, apomixis was defined by Winkler as replacement of the normal sexual reproduction by asexual reproduction, without fertilization. This definition notably does not mention meiosis...
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 by most European experts now treated 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
Stolon
In biology, stolons are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external skeletons.-In botany:...
s (runners like those of strawberries) and by seeds, whereas true Hieracium species only reproduce 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.
Common names
HawkweedFlowers and flower-heads
Hieracium or Hawkweeds, like the others in the Asteraceae family have mostly yellowYellow
Yellow is the color evoked by light that stimulates both the L and M cone cells of the retina about equally, with no significant stimulation of the S cone cells. Light with a wavelength of 570–590 nm is yellow, as is light with a suitable mixture of red and green...
,
tightly packed flower-heads
Head (botany)
The capitulum is considered the most derived form of inflorescence. Flower heads found outside Asteraceae show lesser degrees of specialization....
of numerous small flowers
but unlike daisies
Bellis perennis
Bellis perennis is a common European species of Daisy, often considered the archetypal species of that name. Many related plants also share the name "Daisy", so to distinguish this species from other daisies it is sometimes qualified as Common Daisy, Lawn Daisy or occasionally English daisy. It is...
and sunflower
Sunflower
Sunflower is an annual plant native to the Americas. It possesses a large inflorescence . The sunflower got its name from its huge, fiery blooms, whose shape and image is often used to depict the sun. The sunflower has a rough, hairy stem, broad, coarsely toothed, rough leaves and circular heads...
s in the same family, they have not two kinds of florets but only strap-shaped (spatulate) florets, each one of which is a complete flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
in itself, not lacking stamens,
and joined to the stem by leafy bracts. Like other tribe Cichorieae members each ray corolla is tipped by 3 to 5 teeth.
Bracts, stems and leaves
Erect single, glabrous or hairy stemsPlant stem
A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , conifer cones, roots, other stems etc. The internodes distance one node from another...
, 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; "stellate-pubescent
Trichome
Trichomes are fine outgrowths or appendages on plants and certain protists. These are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae.- Algal trichomes :...
" 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
Bract
In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis, or cone scale. Bracts are often different from foliage leaves. They may be smaller, larger, or of a different color, shape, or texture...
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
Cichorieae
Cichorieae is a tribe of plants in the family Asteraceae that includes 100 genera and more than 1,600 species. They are found primarily in temperate regions of the Eastern Hemisphere....
, Hieraciums contain a milky latex.
Fruits
Distribution
Hieracium species are native to AfricaAfrica
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
,Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
, Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, Central America
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...
and South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
.
Species
The classification of Hieracium into species is notoriously difficult. One reason is the 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.United States
The list below is a selection of species which have been accepted by the USDA Natural Resources Conservation ServiceNatural Resources Conservation Service
The Natural Resources Conservation Service , formerly known as the Soil Conservation Service , is an agency of the United States Department of Agriculture that provides technical assistance to farmers and other private landowners and managers.Its name was changed in 1994 during the Presidency of...
.
A more complete list is given in List of Hieracium species.
- Hieracium albiflorumHieracium albiflorumThe common wildflower Hieracium albiflorum is known by the names white hawkweed and white-flowered hawkweed.It is found in western North America, from Alaska to California and east to the Rockies...
Hook. -- white hawkweed P - Hieracium × alleghaniense Britt. (pro sp.) P
- Hieracium argutumHieracium argutumHieracium argutum is a species of flowering plant in the aster family known by the common name southern hawkweed. It is endemic to California, where it can be found in coastal and inland hills and mountains, often in oak woodland and pine forest habitat...
Nutt. -- southern hawkweed P - Hieracium × atramentarium (Naegeli & Peter) Zahn ex Engl. (pro sp.) P
- Hieracium atratum Fries—polar hawkweed P
- Hieracium aurantiacum L. -- orange hawkweed P
- Hieracium bolanderi Gray—Bolander's hawkweed P
- Hieracium × brachiatum Berth. ex DC. P
- Hieracium caespitosumHieracium caespitosumHieracium caespitosum...
Dumort. -- meadow hawkweed P - Hieracium canadense Michx. -- Canadian hawkweed P
- Hieracium carneum Greene—Huachuca hawkweed P
- Hieracium cynoglossoidesHieracium albertinumHieracium albertinum, known as Western Hawkweed or Houndstongue Hawkweed, is a species of the Hieracium genus that is very similar to Hieracium albiflorum with white flowers but differs in that the flower heads are clustered and the leaves, stems and bracts are covered in a thick layer of hairs...
Arv.-Touv. -- houndstongue hawkweed P - Hieracium × fassettii Lepage P
- Hieracium fendleri Schultz-Bip. -- yellow hawkweed P
- Hieracium × fernaldii Lepage P
- Hieracium × flagellare Willd. (pro sp.) P
- Hieracium × floribundum Wimmer & Grab. (pro sp.) P
- Hieracium × fuscatrum Naegeli & Peter (pro sp.) P
- Hieracium glomeratum Froel. -- queen-devil hawkweed P
- Hieracium gracile Hook. -- slender hawkweed P
- Hieracium greeneiHieracium greeneiHieracium greenei is a species of hawkweed known by the common name Greene's hawkweed....
Gray—Greene's hawkweed P - Hieracium greenii Porter & Britt. -- Maryland hawkweed P
- Hieracium × grohii Lepage P
- Hieracium gronovii L. -- queendevil P
- Hieracium horridumHieracium horridumHieracium horridum,known as the Prickly Hawkweed or Shaggy Hawkweed, gets its name from the long, dense, shaggy white to brown hairs which cover all of the plant partsof this native western North American perennial plant....
Fries -- prickly hawkweed P - Hieracium kalmii L. -- Kalm's hawkweed P
- Hieracium lachenaliiHieracium lachenaliiHieracium lachenalii also known as Common Hawkweed or Yellow Hawkweed is a woodland perennial which makes its home in fields and on roadsides.-Description:...
K.C. Gmel. -- common hawkweed P - Hieracium lactucella Wallr. -- European hawkweed P
- Hieracium laevigatumHieracium laevigatumHieracium laevigatum or Smooth Hawkweed is very similar to Hieracium sabaudum and can be found on dry, more or less nutrient rich soil in light woods, grassy embankments and fields, or on walls.- Distribution :H...
Willd. -- smooth hawkweed P - Hieracium lemmonii Gray—Lemmon's hawkweed P
- Hieracium longiberbe T.J. Howell—longbeard hawkweed P
- Hieracium longipilum Torr. -- hairy hawkweed P
- Hieracium maculatum Sm. -- spotted hawkweed P
- Hieracium marianum Willd. -- Maryland hawkweed P
- Hieracium megacephalon Nash—coastal plain hawkweed P
- Hieracium murorum L. -- wall hawkweed P
- Hieracium paniculatum L. -- Allegheny hawkweed P
- Hieracium pilosella L. -- mouseear hawkweed P
- Hieracium piloselloidesHieracium piloselloidesHieracium piloselloides is a species of flowering plant in the aster family known by the common name tall hawkweed. It is native to Europe and it is present in North America as an introduced species and a common weed....
Vill. -- tall hawkweed P - Hieracium praealtum Vill. ex Gochnat—kingdevil P
- Hieracium pringlei Gray—Pringle's hawkweed P
- Hieracium robinsonii (Zahn) Fern. -- Robinson's hawkweed P
- Hieracium rusbyi Greene—Rusby's hawkweed P
- Hieracium sabaudumHieracium sabaudumHieracium sabaudum, also known as New England Hawkweed, is a species in the Asteraceae.- Common names :...
L. -- New England hawkweed P - Hieracium scabrum Michx. -- rough hawkweed P
- Hieracium schultzii Fries—roughstem hawkweed P
- Hieracium scouleriHieracium scouleriHieracium scouleri is a species of hawkweed known by the common name Scouler's woollyweed. It is native to western North America from Manitoba to California, where it grows in a variety of mountainous habitats. This plant produces a basal rosette of long, narrow leaves 10 to 20 centimeters long,...
Hook. -- Scouler's woollyweed P - Hieracium scribneri Small—Scribner's hawkweed P
- Hieracium triste Willd. ex Spreng. -- woolly hawkweed P
- Hieracium umbellatum L. -- narrowleaf hawkweed P
- Hieracium venosum L. -- rattlesnakeweed P
Plant pest
All species of the genus Hieracium are classed as invasive speciesInvasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
throughout New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
. They are banned from sale, propagation and distribution under the National Pest Plant Accord
National Pest Plant Accord
The National Pest Plant Accord identifies pest plants that are prohibited from sale and commercial propagation and distribution across New Zealand....
. 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 forest, to native Southern Beech
Nothofagus
Nothofagus, also known as the southern beeches, is a genus of 35 species of trees and shrubs native to the temperate oceanic to tropical Southern Hemisphere in southern South America and Australasia...
forest.
In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, many species of Hieracium have been introduced and all species present are considered noxious weeds
Noxious weeds
A noxious weed is an invasive species of a plant that has been designated by country, state or provincial, or national agricultural authorities as one that is injurious to agricultural and/or horticultural crops, natural habitats and/or ecosystems, and/or humans or livestock...
in one or more states.
Further reading
- McCosh, D. and Rich, T.C.G. 209. Hieracium proximum (Caithness Hawkweed) in Ireland. Ir. Nat J. 30: 54.
- Rich,T.C.G., Cotton, D.C.F., Hood, R.L.I.B., Houston, L., McCosh, J. and Jackson, M.B.W. 2009. Conservation of Ireland's biodiversity: status of the Irish endemic Hieracium basalticola Pugsley (Basalt Hawkweed) (Asteraceae). Ir. Nat J. 30: 79 - 89.