Sonchus is a genus of flowering plants in the tribe Cichorieae within the family Asteraceae[ Linnaeus, Carl von. 1753. Species Plantarum 2: 793-795 in Latin] and are commonly known as sow thistles (less commonly hare thistles or hare lettuces). Sowthistles are annual, biennial or perennial herbs, with or without rhizomes and a few are even woody (subgenus Dendrosonchus, restricted to the Canary Islands and Madeira).[For a recent review of woody species, see Seung-Chul Kim et al. (1996). "A common origin for woody Sonchus and five related genera in the Macaronesian islands: Molecular evidence for extensive radiation." Proceedings of the National Academy of Sciences USA, 93:7743-7748.][ Altervista Flora Italiana genere Sonchus photos and distribution maps for several species][ Atlas of Living Australia][ Flora Zambesiaca]
Description
The genus is named after the
Ancient Greece for such plants,
σόγχος. All are characterized by soft, somewhat irregularly lobed
leaves that clasp the stem and, at least initially, form a basal rosette. The
Plant stem contains a milky
latex. Flower heads are yellow and range in size from half to one inch in diameter; the
flower are all of ray type.
Sonchus fruits are single-seeded, dry and indehiscent.
Sow thistles are common roadside plants, and while native to
Eurasia and tropical
Africa, they are found almost worldwide in
temperate regions.
Mature sow thistle stems can range from 30 cm to 2 m (1 to 6 ft) tall, depending upon species and growing conditions. Coloration ranges from green to purple in older plants. Sow thistles exude a milky latex when any part of the plant is cut or damaged, and it is from this fact that the plants obtained the common name, "sow thistle", as they were fed to lactating pig in the belief that milk production would increase. Sow thistles are known as "milk thistles" in some regions, although milk thistle more commonly refers to the genus Silybum.
Comparison with dandelions
They superficially resemble and are in the same family as
Taraxacum, and even have pappus-like structures resembling dandelion seeds. However, they are usually taller than dandelions, have multiple flowers per stem (as opposed to one flower per dandelion), and have more irregularly shaped lobes.
Species
The following 106 species are accepted by Plants of the World Online .
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Sonchus acaulis
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Sonchus x aemulus
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Sonchus afromontanus
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Sonchus araraticus
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Sonchus arboreus
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Sonchus arvensis
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Sonchus asper
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Sonchus x beltraniae
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Sonchus berteroanus
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Sonchus bipontini
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Sonchus bornmuelleri
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Sonchus bourgeaui
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Sonchus brachylobus
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Sonchus brachyotus
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Sonchus brassicifolius
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Sonchus briquetianus
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Sonchus bupleuroides
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Sonchus camporum
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Sonchus canariensis
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Sonchus capillaris
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Sonchus cavanillesii
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Sonchus congestus
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Sonchus crassifolius
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Sonchus daltonii
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Sonchus dregeanus
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Sonchus erzincanicus
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Sonchus esperanzae
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Sonchus fauces-orci
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Sonchus fragilis
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Sonchus friesii
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Sonchus fruticosus
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Sonchus gandogeri
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Sonchus gigas
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Sonchus gomeraensis
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Sonchus grandifolius
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Sonchus gummifer
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Sonchus heterophyllus
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Sonchus hierrensis
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Sonchus hotha
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Sonchus hydrophilus
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Sonchus integrifolius
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Sonchus jacottetianus
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Sonchus jainii
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Sonchus x jaquiniocephalus
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Sonchus kirkii
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Sonchus laceratus
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Sonchus latifolius
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Sonchus leptocephalus
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Sonchus lidii
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Sonchus lobatiflorus
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Sonchus luxurians
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Sonchus macrocarpus
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Sonchus maculigerus
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Sonchus malayanus
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Sonchus marginatus
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Sonchus maritimus
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Sonchus masguindalii
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Sonchus mauritanicus
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Sonchus x maynari
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Sonchus megalocarpus
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Sonchus melanolepis
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Sonchus micranthus
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Sonchus microcarpus
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Sonchus microcephalus
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Sonchus nanus
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Sonchus neriifolius
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Sonchus novae-zelandiae - also known as Kirkianella novae-zelandiae
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Sonchus x novocastellanus
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Sonchus obtusilobus
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Sonchus oleraceus
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Sonchus ortunoi
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Sonchus palmensis
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Sonchus palustris
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Sonchus parathalassius
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Sonchus pendulus
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Sonchus phoeniciformis
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Sonchus pinnatifidus
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Sonchus pinnatus
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Sonchus pitardii
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Sonchus platylepis
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Sonchus x prudhommei
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Sonchus pruinatus
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Sonchus pustulatus
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Sonchus radicatus
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Sonchus regis-jubae
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Sonchus regius
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Sonchus x rokosensis
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Sonchus x rotundilobus
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Sonchus x rupicola
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Sonchus saudensis
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Sonchus schweinfurthii
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Sonchus sinuatus
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Sonchus sosnowskyi
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Sonchus splendens
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Sonchus stenophyllus
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Sonchus suberosus
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Sonchus sventenii
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Sonchus tectifolius
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Sonchus tenerrimus
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Sonchus transcaspicus
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Sonchus tuberifer
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Sonchus ustulatus
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Sonchus webbii
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Sonchus wightianus
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Sonchus wildpretii
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Sonchus wilmsii
Invasive
In many areas sow thistles are considered
,
as they grow quickly in a wide range of conditions and their wind-borne
allow them to spread rapidly.
Sonchus arvensis, the perennial sow thistle, is considered the most economically detrimental, as it can crowd commercial
agriculture, is a heavy consumer of
nitrogen in
, may deplete soil water of land left to
fallow, and can regrow and sprout additional plants from its creeping
. However, sow thistles are easily uprooted by hand, and their soft stems present little resistance to slashing or mowing.
Most livestock will readily devour sow thistle in preference to grass, and this lettuce-relative is edible and nutritious to humans—in fact this is the meaning of the second part of the Latin name of the common sow thistle, oleraceus.[ Arthur Lee Jacobson website ] Attempts at weed control by herbicidal use, to the neglect of other methods, may have led to a proliferation of these species in some environments.[ Management of common sow thistle, Queensland Government
]
Cultivation and use as food
Sow thistles are common host plants for
aphids. Gardeners may consider this a benefit or a curse; aphids may spread from sow thistle to other plants, but alternatively the sow thistle can encourage the growth of beneficial predators such as
hoverfly. In this regard sow thistles make excellent sacrificial plants.
Sonchus species are used as food plants by the
of some
Lepidoptera including
Celypha rufana and the broad-barred white,
grey chi, nutmeg, and shark moths. The
fly Tephritis formosa is known to attack the capitula of this plant.
Sow thistles have been used as fodder, particularly for , hence the other common names of "hare thistle" or "hare lettuce". They are also edible to as a leaf vegetable; old leaves and stalks can be bitter but young leaves have a flavour similar to lettuce. Going by the name pūhā or rareke ( raraki) it is a traditional food eaten in New Zealand by Māori. When cooked the flavour is reminiscent of chard. The greens were also eaten by the indigenous people of North America. Edible raw when young, the older greens can also be eaten after cooking briefly.
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