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Overview

Comprehensive Description

Description

Erect annual herb. Stems simple or sparingly-branched, up to 1.2 m. Leaves linear to linear-lanceolate. Inflorescence a large terminal compound panicle. Capitula numerous, small, funnel-shaped with minute white ray-florets and yellow disk-florets.
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Derivation of specific name

canadensis: of Canada
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Comments

Initially, Horseweed may appear to be a tall, columnar goldenrod with hairy stems, and leaves that tend to angle upward from their bases. However, it dull inflorescence sets it apart. Upon close inspection, the tiny flowers have some resemblance to the more attractive flowers of the Erigeron spp. (Fleabanes), to which genus this plant was assigned in the past. Return
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Description

This native annual plant is 1-7' tall and unbranched, except for the flowering stems near the apex. The stout central stem is ridged and covered with long white hairs. The leaves alternate all around this stem (appearing almost whorled) and differ little in length, except beneath the inflorescence, creating a columnar effect. They are about 3-4" long and ½" across, narrowly lanceolate or oblanceolate, with a few teeth toward the outer tips, and fine white hairs along their margins. The smaller leaves near the inflorescence are more linear and less likely to have any teeth. When mature, several flowering stems appear at the apex, which branch frequently and spread upward and outward, terminating in a multitude of tiny composite flowers. These composite flowers are individually less than 1/8" across, but subtended by smooth green bracts that are somewhat longer. In each composite flower, there are numerous yellow disk florets in the center, which are surrounded by tiny white ray florets that remain erect, rather than spreading outward. There is no noticeable floral scent. The blooming period can occur any time from mid-summer to the fall, lasting about 2-3 weeks for individual plants. The small slender achenes are light brown and have tufts of white or light brown hair. Seed distribution is by wind. The root system consists of a branching taproot.
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Miscellaneous Details

"Notes: Western Ghats, Naturalized, Native of North America"
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Miscellaneous Details

Notes: Moist Deciduous Forests
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Brief

Flowering class: Dicot Habit: Herb
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Distribution

Worldwide distribution

Originating from temperate North America, but now a widespread weed.
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Range and Habitat in Illinois

Horseweed is a very common plant that occurs in every county of Illinois (see Distribution Map). In black soil prairies, it may appear in dry disturbed areas, particularly near the margins of more developed areas, such as fields. It can also be found in dry disturbed areas of gravel prairies, clay prairies, hill prairies, clay banks along rivers, and meadows near woodlands. In more developed areas, Horseweed often appears in abandoned fields, pastures, fence rows, vacant lots, garbage dumps, areas along railroads and roadsides, or in gardens and lawns. This plant is more common in disturbed areas. It has become an adventive weed in Europe.
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National Distribution

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

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National Distribution

Canada

Origin: Exotic

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

United States

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

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National Distribution

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

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National Distribution

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

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"Karnataka: Mysore Tamil Nadu: Dindigul, Nilgiri, Theni"
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"
Global Distribution

India, Nepal, Pakistan and North America

Indian distribution

State - Kerala, District/s: Kottayam, Kollam, Pathanamthitta, Palakkad, Thiruvananthapuram, Kozhikkode, Wayanad, Idukki

"
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"Kerala: Kollam, Kottayam, Kozhikode, Palakkad, Pathanamthitta, Thiruvananthapuram"
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Distribution in Egypt

Sinai.

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Global Distribution

Native to north and south America, widely naturalized in temperate regions.

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A cosmopolitan weed of N. American origin.
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Physical Description

Morphology

Description

Plants erect, (3–)50–200(–350+) cm, branched mostly distally. Leaves: faces usually glabrate (proximal margins ± ciliolate, hairs usually stiff, spreading and hispid on nerves, hairs erect); proximal blades oblanceolate to linear, 20–50(–100+) × 4–10(–15+) mm, toothed to entire; distal similar, smaller, entire. Heads usually in paniculiform, sometimes corymbiform arrays. Involucres 3–4 mm. Phyllaries usually glabrous, sometimes sparsely strigose (margins chartaceous to scarious); outer greenish to stramineous, lanceolate to linear, shorter; inner stramineous to reddish, lance-attenuate to linear. Receptacles 1–1.5(–3) mm diam. in fruit. Pistillate florets 20–30(–45+); corollas ± equaling or surpassing styles, laminae 0.3–1 mm. Disc florets 8–30+. Cypselae uniformly pale tan to light gray-brown, 1–1.5 mm, faces sparsely strigillose; pappi of 15–25, white bristles 2–3 mm. 2n = 18.
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Elevation Range

450-2500 m
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Diagnostic Description

Diagnostic

"Slender erect herbs, 50 cm to more than 2 m in height, nearly smooth or bristly hairy, unbranched at base, branched near top with many small flower heads. Leaves alternate, often appearing opposite, basal and lower stem leaves 2.5 - 10 x 1 cm, strap-shape, entire or toothed, medium and upper stem leaves smaller, sessile, entire, very narrow, soft hairy at first but becoming harsh on older leaves. Flower heads small, numerous on many short branches at top of stem, about 5 mm in diameter; involucre of 2 or 3 series of very small, pointed, greenish bracts 2.5 to 5 mm long; receptacle flat, 1.2 to 2.5 mm broad when bare. Ray florets very short, usually concealed by slightly longer involucral bracts around each flower, greenish white to lavender, pistillate, more than 100 per head, about as long as disk florets; disk florets numerous, bisexual. Achene, cylindrical, elongated, broadest above the middle, somewhat tapering toward scar that has attached light-colored collar, apex truncate, surface is longitudinally grooved and has scattered white hairs, 1.3 x 0.3 mm, pappus of 10 or up to 200 hairs, brownish yellow, 1.5 to 3 times longer than achene."
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Diagnostic

Habit: Herb
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Diagnostic

Habit: Herb
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Synonym

Erigeron canadensis Linnaeus, Sp. Pl. 2: 863. 1753 (as canadense); Conyza canadensis var. glabrata (A. Gray) Cronquist; C. canadensis var. pusilla (Nuttall) Cronquist; C. parva Cronquist; E. canadensis var. pusillus (Nuttall) B. Boivin
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Type Information

Isotype for Erigeron canadensis var. glabratus A. Gray
Catalog Number: US 69201
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Preparation: Pressed specimen
Collector(s): F. J. Lindheimer
Year Collected: 1847
Locality: North of Llano River., Texas, United States, North America
  • Isotype: Gray, A. 1850. Boston J. Nat. Hist. 6 (2): 220.
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Ecology

Habitat

Range and Habitat in Illinois

Horseweed is a very common plant that occurs in every county of Illinois (see Distribution Map). In black soil prairies, it may appear in dry disturbed areas, particularly near the margins of more developed areas, such as fields. It can also be found in dry disturbed areas of gravel prairies, clay prairies, hill prairies, clay banks along rivers, and meadows near woodlands. In more developed areas, Horseweed often appears in abandoned fields, pastures, fence rows, vacant lots, garbage dumps, areas along railroads and roadsides, or in gardens and lawns. This plant is more common in disturbed areas. It has become an adventive weed in Europe.
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General Habitat

Moist deciduous forests and grasslands
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Waste ground, edges of cultivation.

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Associations

Insects whose larvae eat this plant species

Hyalites rahira rahira (Marsh acraea)
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Faunal Associations

Wasps and flies are the most common visitors of the flowers, where they seek nectar. Among the wasp visitors, this includes Sphecid wasps, Vespid wasps, and Ichneumonid wasps. Among the flies, this includes Syrphid flies, Thick-headed flies, Tachinid flies, Flesh flies, Blow flies, and Muscid flies. A few small bees may also visit the flowers. Fertile seed can be produced without cross-pollination. Some insects have been observed feeding on this plant, including the caterpillars of Agrapha oxygramma (Sharp-Stigma Loop Moth), and Nysius niger (Black Seed Bug). Mammalian herbivores usually leave this plant alone because the foliage is bitter. Rabbits may eat the tops off of young plants occasionally. The ecological value of this plant to wildlife is low, except to some flower-visiting insects.
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Flower-Visiting Insects of Horseweed in Illinois

Conyza canadensis (Horseweed)
(Bees collect pollen or suck nectar; flies feed on pollen or suck nectar; other insects suck nectar; some observations are from Robertson, otherwise they are from Graenicher, Moure & Hurd, and Krombein et al. as indicated below)

Bees (long-tongued)
Anthophoridae (Epeolini): Epeolus pusillus sn

Bees (short-tongued)
Halictidae (Halictinae): Agapostemon sericea sn (Gr), Augochlorella striata sn (Gr), Halictus ligatus (MH), Halictus sp. (Lasioglossum sp.) sn (Gr), Halictus rubicunda sn (Gr), Lasioglossum albipennis sn (Gr), Lasioglossum cinctipes sn (Gr), Lasioglossum connexus sn cp (Gr), Lasioglossum coriaceus sn (Gr), Lasioglossum imitatus sn cp (Gr), Lasioglossum pilosus pilosus sn (Gr), Lasioglossum tegularis sn cp (Gr), Lasioglossum versatus sn cp (Rb, Gr), Lasioglossum zephyrus sn (Gr); Halictidae (Sphecodini): Sphecodes prosphorus sn (Gr); Colletidae (Hylaeinae): Hylaeus mesillae (Kr); Andrenidae (Panurginae): Calliopsis andreniformis cp (Kr)

Wasps
Sphecidae (Crabroninae): Anacrabro ocellatus, Ectemnius dives (Gr), Ectemnius lapidarius (Gr), Lestica confluentus (Gr), Lestica producticollis (Gr); Sphecidae (Larrinae): Larra analis (Gr), Tachytes distinctus; Sphecidae (Philanthinae): Cerceris clypeata (Rb, Gr), Cerceris deserta (Gr), Eucerceris fulvipes (Gr), Eucerceris zonata; Vespidae: Dolichovespula arenaria (Gr), Polistes fuscata; Vespidae (Eumeninae): Ancistrocerus adiabatus (Rb, Gr), Eumenes fraterna (Gr), Euodynerus foraminatus (Gr), Stenodynerus anormis (Gr), Symmorphus cristatus (Gr); Chrysididae: Ceratochrysis perpulchra (Gr); Perilampidae: Perilampus hyalinus sn fq (Gr); Gasteruptiidae: Gasteruption tarsatorius (Gr); Ichneumonidae: Ceratogastra ornata

Flies
Syrphidae: Allograpta obliqua (Gr), Eristalis tenax sn, Paragus bicolor (Gr), Sphaerophoria contiqua (Gr), Syritta pipiens sn (Rb, Gr), Toxomerus geminatus (Gr), Toxomerus marginatus sn (Rb, Gr); Conopidae: Thecophora occidensis sn; Tachinidae: Cylindromyia dosiades (Gr), Cylindromyia fumipennis sn, Leucostoma simplex (Gr); Sarcophagidae: Helicobia rapax (Gr), Sarcophaga sp. (Gr), Sarcophaga sarracenioides (Gr), Sphixapata trilineata sn; Anthomyiidae: Delia platura (Gr); Calliphoridae: Pollenia rudis sn; Muscidae: Musca domestica sn, Neomyia cornicina sn; Sciaridae: Sciara fuliginosus (Gr); Tephritidae: Euraresta bella (Gr); Agromyzidae: Melanagromyza aeneoventris (Gr)

Beetles
Coccinellidae: Coccinella novemnotata sn (Gr)

Plant Bugs
Miridae: Adelphocoris rapidus (Gr), Cimex ruficornis (Gr), Lygus lineolaris (Gr), Metriorrhynchomiris dislocatus (Gr), Plagiognathus sp. (Gr); Thyreocoridae: Corimelaena pulicarius (Gr)

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In Great Britain and/or Ireland:
Foodplant / parasite
sporangium of Basidiophora entospora parasitises live Conyza canadensis

Foodplant / sap sucker
adult of Neides tipularius sucks sap of Conyza canadensis

Foodplant / feeds on
larva of Olibrus corticalis feeds on Conyza canadensis

Foodplant / parasite
cleistothecium of Podosphaera fusca parasitises live Conyza canadensis

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Population Biology

Frequency

Frequent
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Life History and Behavior

Cyclicity

Flowering and fruiting: June-August
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Molecular Biology and Genetics

Molecular Biology

Barcode data: Conyza canadensis

The following is a representative barcode sequence, the centroid of all available sequences for this species.


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Statistics of barcoding coverage: Conyza canadensis

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 5
Specimens with Barcodes: 32
Species With Barcodes: 1
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Statistics of barcoding coverage: Erigeron canadensis

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 4
Species With Barcodes: 1
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Conservation

Conservation Status

National NatureServe Conservation Status

United States

Rounded National Status Rank: N5 - Secure

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NatureServe Conservation Status

Rounded Global Status Rank: T5 - Secure

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National NatureServe Conservation Status

Canada

Rounded National Status Rank: NNA - Not Applicable

United States

Rounded National Status Rank: NNR - Unranked

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NatureServe Conservation Status

Rounded Global Status Rank: T4 - Apparently Secure

Reasons: Occurs throughout western North America.

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National NatureServe Conservation Status

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N5 - Secure

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NatureServe Conservation Status

Rounded Global Status Rank: T5 - Secure

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National NatureServe Conservation Status

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N5 - Secure

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NatureServe Conservation Status

Rounded Global Status Rank: G5 - Secure

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Management

These species are introduced in Switzerland.
  • Aeschimann, D. & C. Heitz. 2005. Synonymie-Index der Schweizer Flora und der angrenzenden Gebiete (SISF). 2te Auflage. Documenta Floristicae Helvetiae N° 2. Genève.   http://www.crsf.ch/ External link.
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Relevance to Humans and Ecosystems

Benefits

Cultivation

The preference is full sun, moist to dry conditions, and rich fertile soil. However, this plant flourishes in other kinds of soil, including those containing considerable amounts of gravel and clay. This weedy plant is easy to grow, and sometimes forms large colonies in favorable disturbed sites. Drought resistance is very good.
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Economic Uses

Uses: MEDICINE/DRUG

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Wikipedia

Conyza canadensis

Canadian fleabane (Conyza canadensis) essential oil in a clear glass vial

Conyza canadensis (formerly Erigeron canadensis L.) is an annual plant native throughout most of North America and Central America. Common names include Horseweed, Canadian Horseweed, Canadian Fleabane, Coltstail, Marestail and Butterweed.

Description[edit]

It is an annual plant growing to 1.5 m tall, with sparsely hairy stems. The leaves are unstalked, slender, 2–10 cm long and up to 1 cm broad, with a coarsely toothed margin. They grow in an alternate spiral up the stem and the lower ones wither early. The flowers are produced in dense inflorescences 1 cm in diameter. Each individual flower has a ring of white or pale purple ray florets and a centre of yellow disc florets. The fruit is a cypsela tipped with dirty white down. [1]

C. canadensis can easily be confused with C. sumatrensis, which may grow to a height of 2 m, and the more hairy C. bonariensis which does not exceed 1 m. C. canadensis is distinguished by bracts that have a brownish inner surface and no red dot at the tip, and are free (or nearly free) of the hairs found on the bracts of the other species.[2] [3]


Distribution and habitat[edit]

Horseweed originated in North America but has spread to inhabited areas of most of the temperate zone of the northern hemisphere.[1] It is much the most common of the alien Conyza species in Britain, and is found from northern Scotland to Cornwall. It is the only one of the British Conyza species that grows as a weed of arable land: the others are casuals of waste and disturbed ground in towns and by roads and railways. It is not invasive of any natural or semi-natural habitats.

Weed status[edit]

Horseweed is commonly considered a weed, and in Ohio it has been declared a noxious weed.[4] It can be found in fields, meadows, and gardens throughout its native range. Horseweed infestations have reduced soybean yields by as much as 83%. It is an especially problematic weed in no-till agriculture, as it is often resistant to glyphosate and other herbicides. Farmers are advised to include 2,4-D or dicamba in a burndown application prior to planting to control horseweed. However, evidence exists that horseweed may be able to develop resistance to 2,4-D.[5]

Uses[edit]

The Zuni people insert the crushed flowers of the canadensis variety into the nostrils to cause sneezing, relieving rhinitis.[6] It is valued by Native Americans for assisting in the clotting of the blood and it has also been used to treat rheumatic complaints and gout. A tincture is made from the dried flowering tops of the plants.[1]

References[edit]

  1. ^ a b c "Canadian Fleabane: Conyza canadensis". NatureGate. Retrieved 2013-12-31. 
  2. ^ Conyza sumatrensis, International Environmental Weed Foundation
  3. ^ Green, Deane. "Horseweed, Marestail". Retrieved 2014-08-09. 
  4. ^ Germplasm Resources Information Network: Conyza canadensis
  5. ^ http://www.bioone.org/doi/abs/10.1614/WS-D-10-00022.1
  6. ^ Stevenson, Matilda Coxe 1915 Ethnobotany of the Zuni Indians. SI-BAE Annual Report #30 (p.55)
  • A. Davis, K. Renner, C. Sprague, L. Dyer, D. Mutch (2005). Integrated Weed Management. MSU.
  • Everitt, J.H.; Lonard, R.L.; Little, C.R. (2007). Weeds in South Texas and Northern Mexico. Lubbock: Texas Tech University Press.  ISBN 0-89672-614-2
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Notes

Comments

Conyza canadensis is thought to be native to North America and is now widely adventive, e.g., in South America, Europe, Asia, and Africa. Plants with stems glabrous and phyllaries red-tipped are sometimes treated as var. pusilla; similar plants with stems glabrous and phyllaries stramineous (not red-tipped) are sometimes treated as var. glabrata.
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© Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA

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