Sonchus arvensis Linnaeus
The words or terms in red
(actually dark orange) in the text are defined in a
Sonchus arvensis is a vigorous
with milky sap
and creeping roots that produce new shoots; the plants are up to 1.8 m tall.
They are highly competitive, persistent, at times noxious,
and can rapidly colonize new sites by
Introduced from Europe, it is now
naturalized in North America.
It was probably introduced via contaminated commercial seed.
The North American sighting of the species was from Pennsylvania in 1814.
There are two varieties
of Sonchus arvensis in Canada, and
both varieties hybridize; they are:
In some floras these are given
Sonchus arvensis and Sonchus uliginosus respectively.
Both have a hairless lower stem,
but in Sonchus arvensis var. arvensis the upper stem and bracts
have conspicuous gland-tipped hairs.
Sonchus arvensis var. arvensis is most abundant in Ontario,
Québec and the Atlantic provinces.
Sonchus arvensis var. uliginosus is most abundant on the prairies
and extends north to Great Slave Lake.
And some botanists do not recognize these two varieties and state that
Sonchus arvensis var. uliginosus is a synonym for
Sonchus arvensis var. arvensis.
- Sonchus arvensis var. arvensis
- Sonchus arvensis var. uliginosus
The species belongs to the
Many sources, copied from one another ? say that the genus name
is from the Greek sonchos, the plant's initial name, and means
hollow in reference to the stem.
I checked in my Dictionnaire Grec Français by Anatole Bailly,
also called, Le Grand Bailly, one of the quite renowned
dictionary of classical Greek, and I could not find one entry starting in
σον (son) or
σων (sôn), so...
In Latin, arvum means cultivated land, field, pastureland
and arvus means that can be cultivated;
but in the classical Dictionnaire Illustré Latin Français
by Félix Gaffiot, there is no entry for arvensis.
However the Botanical Latin, by William T. Stearn, Fourth Edition,
has an entry for arvalis, arvensis
with the definition pertaining to fields or cultivated land,
and this in one of the habitat of Sonchus arvensis.
Some of the vernacular names of
Sonchus arvensis are:
Creeping Sow Thistle, Field Sow-thistle, Swine-thistle, Milk Thistle,
Field Milk Thistle, Corn Sow-thistle,
Tree Sow-thistle, Dindle and Gutweed
The French vernacular name of Sonchus arvensis is
Laiteron des champs in reference to the milky sap and a common habitat.
The synonymy for Sonchus arvensis, for its two varieties, is:
- Sonchus arvensis subsp. arvensis L.
- Hieracium arvense (L.) Scop.
- Sonchoseris arvensis (L.) Fourr.
- Sonchus arvensis L. var. shumovichii B. Boivin
- Sonchus decorus Castagne
- Sonchus glaber Schult.
- Sonchus mauritanicus Boiss. & Reut.
- Sonchus nitidus Vill.
- Sonchus shzucinianus Turcz. ex Herder
- Sonchus vulgaris Rouy var. decorus (Castagne) Rouy
- Sonchus arvensis subsp. uliginosus (M. Bieb.) Nyman
- Sonchus arvensis L. forma glabrescens
(Günther, Grab. & Wimm.) Kirp.
- Sonchus arvensis L. var. glabrescens
Günther, Grab. & Wimm.
- Sonchus uliginosus M. Bieb.
Sonchus arvensis is not too difficult to identify by its yellow
flower heads, dandelion-like,
with numerous ray flowers,
by its milky sap and its spiny, prickly
It can be confused with
Sonchus asper or
Sonchus oleraceous but the later have
smaller flower heads, 1.5 to 2.5 cm in diameter.
Furthermore, Sonchus asper has
leaves with weak spines
and Sonchus oleraceous has
leaves that are almost spineless.
(Sonchus asper and Sonchus oleraceous are
Sonchus asper is easily distinguished from Lactuca serriola
that has somewhat similar flowers,
but Sonchus arvensis does not have the distinctive ridge of spines
on the midrib on the underside of the leaf that is associated with
Sonchus arvensis is a vigorous
stout, erect, milky-juiced, deep-rooted perennial herb,
from 2 to 5 feet tall, spreading by deep creeping roots.
It reproduces by seed, by thick vertical roots and by
cylindrical horizontal roots.
In established stands, shoots and new roots begin to form when the soil warms.
The shoots develop from buds that overwinter on roots
or the basal portion of aerial stems.
Seeds also germinate around the same time period.
Plants form rosettes early in development,
which provide a large photosynthetic area.
The species can spread rapidly via its spreading root system.
Most plants do not flower during the first-year.
- Often described as rhizomes,
they produce new shoots and fragment easily.
- Horizontal roots long, creeping, of less than 1 cm in diameter,
typically form 5 to 12 cm below soil surface,
can grow to 2 m long or more in a season.
- Vertical roots can penetrate soil to a depth of 2 m and produce
new shoot buds to a depth of 0.5 m.
- Overwintering roots can survive temperatures to -16º C.
hollow, ridged, branched only in the upper portion of the plant.
- Lower stems leafy.
- Upper stems can be glabrous
- With bitter, milky sap.
- Dying back after first frost.
highly variable, entire to
deeply pinnately lobed to
- Lanceolate to
- From 5 to 30 cm long, 2 to 10 cm wide.
- Clasping the stem at the base with rounded basal
- With the lobes more or less triangular, often curved backwards,
usually from 2 to 5 and up to 7 per side.
- The terminal lobe typically longer, broader than lateral lobes.
- With the margins
with small spiny teeth.
- The upper leaves petiole, lobed.
- On an open inflorescence,
containing several to many heads,
- Up to 20 per inflorescence during the flowering season,
but usually only a few heads flower at the same time.
- Measuring from 3 to 5 cm wide.
- With numerous bright yellow to orange-yellow
5-lobed ligulate flowers.
- With flowers not self-fertile.
- With linear phyllaries that are
imbricate, the outer ones much shorter than the inner.
- With the peduncles
(flower head stalk) and phyllaries typically covered with stiff
- With campanulate involucres,
10 to 22 mm high.
- Opening about 2 to 3 hours after sunrise and close around noon.
- Seldom present the first year.
- Blooming from July to September (until frost).
- Pollinated by insects.
- Achenes, more or less oblong,
flattened, 3 to 4 angled with 2 minutely
wrinkled longitudinal ridges between angles;
- Seeds about 2.5 to 3.5 mm long excluding
and about 1 mm wide, light to dark brown.
- With strongly accrescent
pappus of fine, soft, white, numerous
bristles from 8 to 12 mm long.
- The pappus have hooked cells that allow them to stick to clothes,
animal fur, etc.
Sonchus arvensis thrives on non-compacted,
fine, rich, slightly alkaline
to neutral soils. It tolerates some salinity.
It is found on bare ground, in roadsides, in disturbed sites with damp soils,
in ditches and exposed soil, around sloughs and along streams.
In cultivated fields dense stands occur in oilseeds, pulses,
irrigated crops and, to a lesser extent, in cereals.
Seedlings are typically found along pond and river margins and in lawns,
moist meadows, and uncultivated fields.
Since its introduction to North America,
Sonchus arvensis has spread widely throughout
the northern United States and southern Canada.
It is now found in all USA states, including Alaska
but for Arizona, Oklahoma, Alabama, Georgia, South Carolina and Florida.
The plant has also established in South America, Australia, and New Zealand.
Widely established in temperate regions, it is not found in the tropics.
The maps, from Flora of North America show the USA States and Canadian
provinces where Sonchus arvensis var. arvensis (map on the left)
and Sonchus arvensis var. uliginosus (map on the right)
can be found.
Sonchus arvensis occurs in all Canadian provinces
and is continuing to spread north.
It was found in the arctic tundra-boreal forest region of Wood
Buffalo National Park, circa 60 °N, in 1962.
(Buffalo National Park is Canada largest national park and one of the largest
in the world; it was established in 1922 to protect the last remaining herds of
bison in northern Canada; today, it protects an outstanding and representative
example of Canada's Northern Boreal Plains).
In Canada, it is most common in cool moist regions where it does best
with little competition from perennials.
In Europe it is distributed from Scandinavia south to Italy and east to the
western portions of the former Soviet Union.
It is most common in the northwest, less common in central regions
and rare in the south.
Sonchus arvensis is classified as a noxious
weed in many USA states and Canadian provinces;
it a problem in several crops, where it causes economic losses
due to reduced crop yields, increased cultivation and herbicide expenses,
and land depreciation.
At high densities (27 shoots/m2), it has reduced spring wheat yields
up to 45 percent in North Dakota. It is also a host of several
economically important plant pests.
Since Sonchus arvensis is palatable to both sheep and cattle,
pasturing infested land can be an effective control method.
The plant makes acceptable livestock feed
and is excellent feed for rabbits and other foraging animals.
In addition, the roasted roots have been used as a coffee additive
or replacement, and the young leaves can be used in salads.
The plant may have potential for use in oil or hydrocarbon production,
since most of the latex is composed of oil.
The plant is also a source of
which may have use in the pharmaceutical industry.
The leaves have been used as a poultice and are said
to have anti-inflammatory activity.
An infusion of the leaves has been used in the treatment of caked breasts
A tea made from the roots is used in the treatment of asthma,
coughs and other chest complaints.
A tea made from the leaves is said to calm the nerves.
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