Compositae (Asteraceae) - composite family
 

WeedsPoisonous PlantsHay Fever
Gerald A. Mulligan (Agriculture Canada, Ottawa, retired)
Click here to go to Weed Photos for this family

Achillea lanulosa Nutt. [ =Achillea millefolium in the sense of some authors], common yarrow, achillée millefeuille
Perennial, spreading by seeds and shallow, horizontal rootstocks; allogamous; stem to 2 feet (6 dm.) high; flowers white; with the exception of dandelion, common yarrow is the most common weed in our area; pastures, lawns, meadows, roadsides, and waste places; native to North America. Crushed leaves can cause an allergic reaction in some people. Dairy products produced from cows grazing on this plant can have an undesirable flavor.

Acroptilon repens (L.) DC. [ =Centaurea repens L.], Russian, centaurée de Russie
Perennial, forming dense patches; plants 2 to 3 feet (6 to 9 dm.) high; flowers purple to pink early, turning straw colored at maturity; cultivated fields, grain and alfalfa fields, pastures and waste places; a fairly recent introduction, probably as an impurity in Turkestan alfalfa; it has become widespread, especially in the mid-west and near-west. There are reports of it causing poisonings and the deaths of sheep and horses.

Ageratina altissima (L.) King & H. Rob. [=Eupatorium rugosum Houtt.], white snakeroot, eupatoire rugueuse
A perennial herb with stems 1 to 4 ft. (30 to 120 cm) tall. It has short-stalked opposite leaves and inflorescences with 10 to 30 small heads composed entirely of white disk flowers. It is a native plant of open and shady habitats in the eastern half of our area. It is very toxic if eaten. Poisonings and deaths have occurred of cattle, horses, sheep, and goats. There are some early reports of sicknesses and deaths of pioneers who drank milk from cows that had eaten white snakeroot. There are no recent reports.

Ambrosia artemisiifola L., common ragweed, petite herbe à poux
Annual, spreading by seeds; stems erect, usually 2 to 3 feet (6 to 9 dm.) high; flowers inconspicuous, wind pollinated; throughout our area but most common in southern Ontario, Quebec as far as Quebec City and southward in the United States; cultivated fields, gardens, vacant lots, and especially along the fringes of roadsides; native to North America. Its wind-blown pollen is the most important cause of hay fever in eastern North America. Dairy products from cows that have grazed this plant often have an objectionable odor and taste.

Ambrosia psilostachya DC. [ =Ambrosia coronopifolia Torr. & A.Gray], perennial ragweed, herbe à poux vivace
Perennial with horizontal rootstocks; a smaller plant with rougher, thicker, and less lobed leaves than common ragweed, but otherwise similar; flowers inconspicuous, wind pollinated; most common in the mid-west and west, but has recently spread eastward along railroad lines; native to North America. Its wind-blown pollen causes hay fever in humans.

Ambrosia trifida L., giant ragweed, grande herbe à poux
Annual, spreading by seeds; plants 1 to 10 feet (3 to 30 dm.) high; most common in southwestern Quebec, southern Ontario, southern Manitoba, and southward in the United States; flowers inconspicuous, wind pollinated; roadsides, railway lines, agricultural fields, and waste places; native to North America. It is far less abundant than common ragweed and its air-born pollen is less important as a cause of hay fever.

Anthemis cotula L., stinking mayweed, camomille des chiens
Annual, from 6 to 18 inches (15 to 45 cm.) high; most common along the fringes of roadsides and around farm buildings; white ray flowers, yellow disk flowers; it rarely occurs in cultivated fields; throughout our range, except the mid-west; introduced from Europe. Crushed leaves have a strong odor.

Arctium minus Bernh., common burdock, petite bardane
Biennial; autogamous; stems 2 to 6 feet (6 to 18 dm.) high; flowers purple; farm yards, fencerows, roadsides, and waste places; not in cultivated fields; throughout our range, but most common in Eastern North America; introduced from Europe. Forms a large rosette, in the first year, that resembles rhubarb (but is not edible). Mature flowers form prickly burs that stick to clothing and fur.

Arctium tomentosum Mill., woolly burdock, bardane tomenteuse
Biennial with stems 2 to 4 feet (6 to 12 dm.) high; flowers purple; not common but locally abundant in waste places; introduced from Europe.

Artemisia absinthium L., absinth, armoise absinthe
Perennial with stems to 5 feet(15 dm) high; flowers inconspicuous; strongly aromatic; roadsides, waste places, farmyards, pastures ,and cropland; throughout our range but particularly abundant in the mid-west; introduced from Europe. Causes taint in dairy products when eaten by cattle. Absinth is used in the preparation of some alcoholic beverages and was formerly used for medicinal purposes. Its volatile oils are toxic if consumed in large amounts.

Artemisia biennis Willd.- biennial wormwood, armoise bisannuelle
An annual or biennial, scentless, herb; usually with only a single stem. Stems from 1 to 3 feet (3 to 9 dm.) high. Native in the western portion of our area, but probably an introduction in the eastern part. Weedy in disturbed habitats within and outside of its native range.

Artemisia vulgaris L., mugwort, armoise vulgaire
A rhizomatous perennial herb with erect stems from 2 to 8 ft. (6 to 24 dm.) tall. Originally introduced from Europe. Fragments of mugwort rhizomes, readily able to establish new plants, are believed to be its main method of spread. In some cases, mugwort can form dense monospecific stands. Mugwort is widespread along roadsides and in waste places in the eastern half of our range. Oil extracted from its foliage has been used for a variety of purposes.

Aster novae-angliae L. [=Symphyotrichum novae-angliae (L.) G.L.Nelson], New England aster, aster de Nouvelle-Angleterre
New England aster is a perennial herb with single to multiple, densely leafy, erect stems 2 to 5 ft. (60 to 150 cm.) high, with short, thick, underground rhizomes. Flower heads are large and showy, 1.5 in. (ca.4 cm.) in diameter, with yellowish disk flowers surrounded by deep-purple, blue, rose, rarely white, ray flowers. Flowering is normally late, in September and October. It is a native of moist soils along the margins of lakes, streams, and other fresh water bodies. It is a naturalized colonizer along roadsides, railway lines, and in meadows and waste places. Its showy flowers are a colorful addition to the fall landscape. It occurs in all areas except parts of the Midwest. Numerous cultivars have been produced for use as a late-flowering ornamental.

Bidens cernuus L. nodding beggarticks, bident penché
Erect annual native herb from 6 inches to 5 feet (1.5 to 15 dm.) tall. Flower heads nodding; yellowish brown disk flowers are surrounded by, showy, yellow ray flowers. Widespread; occurs along the margins of streams, rivers, ponds, lakes, marshes, bogs, and in other moist habitats. The two-barbed seeds, when mature in late summer and autumn, will adhere readily to clothing and to the fur of animals.

Bidens vulgatus Greene, tall beggarticks, bident vulgaire
Erect annual native herb from 6 inches to 5 feet (1.5 to 15 dm.) tall. Flower heads of tall beggarticks are almost solely composed of disk flowers. Ray flowers are rarely present . Widespread in both wet and dry habitats. Mature two-barbed seeds will adhere to clothing and to the fur of animals.

Carduus acanthoides L., plumeless thistle, chardon épineux
Biennial, spreading by seeds, stems 8 inches to 6 feet (20 cm. to 18 dm.) high; flowers purple, rarely white; pastures, waste places, and along roadsides; locally common in Quebec, Ontario, and British Columbia and southward in the United States; introduced from Europe.

Carduus nutans L., nodding thistle, chardon penché
Biennial, spreading by seeds, stems 1 to 6 feet (3 to 18 dm.) high; flowers purple; locally common throughout; pastures, rangeland, waste places, and along roadsides; introduced from Europe and Asia. Often hybridizes with plumeless thistle.

Centaurea diffusa Lam., diffuse knapweed, centaurée diffuse
Biennial to short-lived perennial; stems 2 to 3 feet (6 to 9 dm.) high; flowers white or purple; very common along roadsides and in dry rangelands in western North America; introduced from Europe.

Centaurea jacea L., brown knapweed, centaurée jacée
Perennial; stems erect, 2 to 4 feet (6 to 12 dm.) high; flowers rose-purple; locally common in pastures, and along roadsides in southwestern Ontario, the Eastern Townships of Quebec, and in the adjacent United States; introduced from Europe.

Centaurea maculosa Lam., spotted knapweed, centaurée maculée
Biennial or short-lived perennial; stems 2 to 6 feet (3 to 9 dm.) high; flowers purple, rarely white; locally common in pastures and waste places in the east; common in the dry rangelands of British Columbia, Washington, Oregon, Idaho, and western Montana; introduced from Europe.

Centaurea nigra L., black knapweed, centaurée noire
Perennial; stems erect, 2 to 4 feet (6 to 12 dm.) high; flowers purple; abundant in pastures, waste places, and along roadsides in maritime-east and maritime-west; sporadic in inland-east; introduced from Europe.

Cichorium intybus L., chicory, chicorée sauvage
Perennial, spreading by seeds; stems 1 to 6 feet (3 to 18 dm.) high; flowers usually bright blue; abundant in hayfields, waste places, and along roadsides in all except the mid-west; introduced from Europe. Cows can produce milk with a bitter flavor after eating large quantities of chicory.

Cirsium arvense (L.) Scop., Canada thistle, chardon des champs
Perennial, spreading by seeds and underground rootstocks; stems 6 inches to 4 feet (15 cm. to 12 dm.) high; allogamous, with male and female flowers on separate plants; flower color varies from white, to pink, rose-purple or purple; an aggressive weed throughout our area; in cultivated fields, meadows, pastures, waste places, and along roadsides; introduced from Europe.

Cirsium vulgare (Savi) Ten., bull thistle, chardon vulgaire
Biennial, spreading by seeds; autogamous; stems 1 to 6 feet (3 to 18 dm.) high; flowers purple; throughout our range, but less common in the mid-west; in pastures, waste places, and along roadsides; introduced from Europe and Asia.

Conyza canadensis (L.) Cronquist [ =Erigeron canadensis L.], Canada fleabane, vergerette du Canada
Annual or winter annual, spreading by seeds; autogamous; stems a few inches to 6 feet (8cm. to 18 dm.) high; flowers small, whitish; throughout our range but less common in maritime areas; in cultivated fields, pastures, meadows, waste places, and along roadsides; native to North America.

Crepis capillaris (L.) Wallr., smooth hawk's-beard, crépis capillaire
Perennial, spreading by seeds; 6 inches to 3 feet (15 cm. to 9 dm.) high; flowers yellow; common in the coastal regions of southern British Columbia, Washington, and Oregon; in meadows, waste places, and along roadsides; introduced from Europe.

Crepis tectorum L., narrow-leaved hawk's-beard, crépis des toits
Annual or winter annual; stems 3 inches to 3 feet (8cm. to 9 dm.) high; flowers yellow; abundant in the mid-west, rare elsewhere; in grain fields, pastures, fallow land, and along roadsides; introduced from Europe and Asia.

Erigeron philadelphicus L., Philadelphia fleabane, vergerette de Philadelphie
Perennial by stolons and offsets; stems 1 to 3 feet (3 to 9 dm.) high; flowers usually a pale pink; throughout our range, but less common in the mid-west and maritime areas; meadows, pastures, swampy ground, woods, riverbanks, beaches, and roadsides; native to North America.

Erigeron strigosus Muhl. ex Willd., rough fleabane, vergerette rude
Annual or biennial; stems 2 to 4 feet (6 to 12 dm.) high; ray flowers usually white; occurs throughout our area; meadows, pastures, and roadsides; native to North America.

Eupatorium maculatum L., spotted Joe-Pye weed, eupatoire maculeé
A fibrous-rooted perennial plant that is a native of moist, open, habitats throughout our area. Plants are from 3 to 6 feet (9 to 18 dm.) tall, with pink to purple flat-topped flower heads.

Galinsoga quadriradiata Ruiz. & Pavón [ =Galinsoga ciliata (Raf.) S.F.Blake], hairy galinsoga, galinsoga cilié
Annual, spreading by seeds; 6 to 24 inches (15 to 60 cm.) high; ray flowers white, disk flowers yellow; occurs throughout our area, but rare in the mid-west; usually in gardens and other habitats in settlements; introduced from South America.

Hieracium aurantiacum L., orange hawkweed, épervière orangée
Perennial, spreading by seeds and leafy runners; apomictic; flowering stems 8 inches to 2 feet (20 cm. to 6 dm.) high; flowers a bright orange-red; mostly in the eastern part of our range, rare in the mid-west and west; old fields, and pastures, meadows, and roadsides; introduced from Europe.

Hieracium pilosella L., mouse-eared hawkweed, épervière piloselle
Perennial with above ground runners; flowering stems 6 to 12 inches (15 to 30 cm.) high; flowers yellow; common in maritime-east, less common elsewhere in the east; roadsides, pastures, and waste land; introduced from Europe.

Hieracium pilloselloides Vill. [ =Hieracium florentinum All.], king devil hawkweed, épervière des Florentins
Perennial with short, thick, rootstocks; apomictic; stems 9 to 12 inches (23 to 30 cm.) high; flowers yellow; abundant in Ontario, western Quebec, western New York, and Pennsylvania, and rare elsewhere; roadsides, pastures, and waste land; introduced from Europe.

Hypochaeris radicata L., spotted cat's-ear, porcelle enracinée
Perennial; stems 6 inches to 2 feet (15 cm. to 6 dm.) high; flowers yellow; common only in the coastal areas of Oregon, Washington, and southern British Columbia; pastures, waste places, and along roadsides; introduced from Europe.

Inula helenium L., elecampane, inule aunée
A coarse perennial herb, with rigid stems from 3 to 6 feet (9 to 18 dm.) high, that was introduced here from Eurasia as an ornamental and medicinal plant. It is an uncommon garden escape in fields, roadsides and waste places, especially near past or present habitations. It occurs in all areas except our Midwest.

Iva axillaris Pursh, povertyweed, ive à fleurs axillaires
Persistent-perennial, spreading by seeds and underground rootstocks; stems 6 to 8 inches (15 to 20 cm.) high; flowers inconspicuous, wind-pollinated; common in the prairie region, less common in dry areas further west; native to the western prairies of the United States and Canada. Where abundant, its wind-blown pollen is an important cause of hay fever.

Iva xanthifolia Nutt., false ragweed, ive à feuilles de lampourde
Annual; stems 3 to 8 feet (9 to 24 dm.) high; flowers inconspicuous, wind-pollinated; common in the mid-west, rare to the east and west; cultivated land, waste land, and gardens; native to North America. The abundant wind-blown pollen is an important cause of hay fever. Contact with leaves produces a dermatitis in some people. Milk from cows grazing this plant has an undesirable flavor.

Lactuca scariola L. [ =Lactuca serriola L.], prickly lettuce, laitue scariole
Annual or winter annual, spreading by seeds; autogamous; stems 1 to 6 feet (3 to 18 dm.) high; flowers yellow; throughout our range, but less common in the mid-west; cultivated land, waste places, and along roadsides; introduced from Europe. The plant has spiny midveins.

Lactuca tatarica (L.) C.A.Mey. subsp. pulchella (Pursh) Stebbins [ =Lactuca pulchella (Pursh) DC.], blue lettuce, laitue bleue
Perennial, with deep rootstocks; stems up to 3 feet (9 dm.) high; flowers blue; mostly in open prairie and rangelands of the west; also in adjacent roadsides and irrigated fields; native to western North America.

Lapsana communis L., nipplewort, lapsane commune
An annual or winter annual with stems 6 to 50 inches (15 to 125 cm) high. Flower heads are yellow, dandelion-like but much smaller at 3/8 to ¾ inch (1 to 2 cm) in diameter. Unlike dandelion, nipplewort has lyrate-lobed lower leaves and its seeds lack a parachute-like pappus. Nipplewort is a native of Europe and western Asia and was apparently introduced into our Continent in the 19th century. It now occurs in most of southern Canada and the northern United States. It is, however, rare or absent in much of the Midwest. Originally only a weed of gardens and waste places, it has now become an important weed of grain, forage and vegetable crops in some areas. It has the chromosome number of 2n= 14.
Text and photos of nipplewort by Stephen J. Darbyshire.

Leontodon autumnalis L., fall hawkbit, liondent d’automne
Perennial, spreading by seeds; stems 4 inches to 2 feet (10 cm. to 6 dm.) high; flowers yellow; most common in the maritime part of Eastern North America; old pastures, meadows, lawns, and waste places. Introduced from Europe and Asia.

Leucanthemum vulgare Lam. [ =Chrysanthemum leucanthemum L.], ox-eye daisy, marguerite blanche
Perennial, spreading by seeds; allogamous; stems 1 to 3 feet (3 to 9 dm.) high; ray flowers white, disk flowers yellow; throughout our range but rare in prairie regions; most plants are diploid, except for tetraploid populations that occur just north and south of the St. Lawrence River; meadows, pastures, waste places, hayfields, and roadsides. Milk can have a disagreeable taste after cows have eaten ox-eye daisy.

Matricaria discoidea DC. [ =Matricaria matricarioides of some authors], pineapple weed, matricaire odorante
Annual, spreading by seeds; autogamous; plants 1 to 8 inches (25 mm. to 20 cm.) high; throughout our range; flower heads yellow; gardens, waste places, playgrounds, and roadsides; frequently growing in trampled soil; native of western North America. Crushed plant parts produce a pineapple odor.

Matricaria perforata Mérat. [ =Matricaria inodora L. & Matricaria maritima L. var. agrestis (Knaf) Wilmott], scentless chamomile, matricaire inodore
Annual to short-lived perennial; plants 6 to 40 inches (15 to 100 cm.) high; ray flowers white, disk flowers yellow; throughout our range, but most common in the maritime areas on both coasts and the mid-west; cultivated fields, roadsides, and waste places; a serious weed in the mid-west; introduced from Europe. Crushed leaves of this plant are scentless, whereas those of the superficially similar stinking mayweed have a strong odor.

Rudbeckia hirta L. var. pulcherrima Farw. [ =Rudbeckia serotina Nutt.], black-eyed Susan, rudbeckie hérissée
Perennial, spreading by seeds; stems 1 to 3 feet (3 to 9 dm.) high; ray flowers orange, disk flowers brown; throughout our range, locally common; hayfields, pastures, rangeland, waste places, and roadsides; native to North America. Ingestion of large quantities can cause severe poisoning of grazing animals.

Senecio jacobaea L., tansy ragwort, séneçon jacobée
Biennial or short-lived perennial; stems 1 to 3 feet (3 to 9 dm.) high; flowers yellow; most common in eastern and western maritime areas, rare elsewhere; pastures, hayfields, roadsides, and waste places; introduced from Europe. Poisoning and death of cattle, sheep, and horses. It usually occurs from animals eating hay contaminated with tansy ragwort. Animals tend to avoid eating plants growing in fields.

Solidago canadensis L., Canada goldenrod, verge d’or du Canada.
Perennial, spreading by seeds and rootstocks; allogamous; stems 18 inches to 5 feet (45 cm. to 15 dm.) high; flowers yellow; in the eastern half of our range; meadows, old fields, roadsides, fencerows, and waste places; native of North America. Contrary to popular belief, the goldenrods are not responsible for hay fever. As a general rule, plants with showy flowers produce relatively small amounts of pollen. Their pollen is sticky and is programmed to adhere to insects and be transferred by them to the stigmas of other flowers that they visit. It is the plants with inconspicuous flowers, that produce large amounts of lighter pollen that is blown indiscriminately by the wind, that causes most hay fever in humans. This “wasteful” strategy requires large amounts of pollen so that it can effectively come in contact with the stigmas of other plants. Since the hay fever season coincides with the simultaneous flowering of common ragweed, with its inconspicuous flowers, and goldenrods, with their conspicuous flowers, the wrong culprit often stands accused.

Sonchus arvensis L., perennial sow-thistle, laiteron des champs
Perennial, spreading by underground rootstocks; allogamous; stems 1 to 5 feet (3 to 15 dm.) high; flowers yellow; throughout our area; a tetraploid, with glabrous bracts and upper stems, is commonest in the mid-west, whereas a hexapoid, with glandular hairs on its bracts and upper stems, is commoner elsewhere; introduced from Europe and Asia.

Sonchus asper (L.) Hill, spiny annual sow-thistle, laiteron rude
Annual, spreading by seeds; stems 1 to 4 feet (3 to 12 dm.) high; flowers yellow; throughout, but less common in the mid-west; cultivated fields, gardens, waste places, and along roadsides; introduced from Europe.

Sonchus oleraceus L., annual sow-thistle, laiteron potager
Annual, spreading by seeds; stems 1 to 4 feet (3 to 12 dm.) high; flowers yellow; throughout our range; gardens, row crops, waste places, and roadsides; introduced from Europe.

Tanacetum vulgare L., tansy, tanaisie vulgare
Perennial herb with stout rhizomes; has a strong aromatic odor; stems erect, 1 to 6 feet (3 to 18 dm) tall; flowers yellow; locally common throughout our area; often forms dense patches in waste areas, ditches, boarders of fields, and along roadsides; originally introduced from Europe and Asia as a medicinal plant.

Taraxacum officinale G.H.Weber ex Wiggers, dandelion, pissenlit officinal
Perennial, with a deep-penetrating tap root, spreading by seeds; stems 3 inches to 1 foot (8 to 30 cm.) high; flowers yellow; one of the most common weeds throughout our range; pastures, lawns, waste places, hayfields, cultivated land, and roadsides; introduced from Europe. Dandelion, like many plants of the composite family, produces seeds attached to a feathery pappus. The seeds attached to this “parachute” are disseminated widely by the wind. In addition, our dandelion is a triploid that is apomictic (does not require fertilization to produce seed). These characteristics, plus a long tap root that can reach to a considerable depth, makes dandelion a very successful colonizer in many habitats over a wide area.

Tragopogon dubius Scop. [ =Tragopogon major Jacq,], goat's-beard, salsifis majeur
Biennial to perennial, spreading by seeds; autogamous; stems 6 inches to 2 feet (15 cm. to 6 dm.) high; flowers yellow; throughout our range, but most common in the mid-west; pastures, prairie, hayfields, waste places, and along roadsides; introduced from Europe.

Tragopogon pratensis L., meadow goat's-beard, salsifis des prés
Biennial to perennial, spreading by seeds; autogamous; stems 1 to 4 feet (3 to 12 dm.) high; flowers yellow; throughout our range, but most common in the eastern half; pastures, hayfields, waste places, and roadsides; introduced from Europe.

Tussilago farfara L., colt’s-foot, tussilage pas-d’âne
A perennial herb that spreads mainly by its extensive system of thick, white, horizontal, underground rhizomes. Bright yellow dandelion-like flowers appear in early spring well before the emergence of large heart-shaped leaves. Flowering stems are gray-wooly and 2 to 20 inches (5 to 50 cm.) tall. Colt’s-foot was introduced here from Europe and Asia for medicinal purposes. It should never be used internally because of its dangerous alkaloids. Colt’s-foot is locally common, in a wide range of habitats, in the eastern and extreme southwestern parts of Canada and in the eastern and northwestern United States. It can be an invasive plant, producing a dense canopy of leaves that will smother other vegetation.

Xanthium strumarium L., cocklebur, lampourde glouteron
Coarse annual herb; erect; 1 to 3 feet (3 to 9 dm) high; most common in moist ground, along shores, and in fields and waste places; widespread; both native and introduced populations occur in our area. Has poisoned cattle, sheep, and swine. Milk from cows grazing on its leaves has a very undesirable flavor. The fruit is bur-like. It often becomes entangled in the manes of farm animals, and it can also contaminate the wool of sheep.

Click on a photo to view an enlarged image.
Weed Name Photo Weed Name Photo
common yarrow, achillée millefeuille
(a large patch)
common yarrow, achillée millefeuille
common yarrow, achillée millefeuille
(summer)
common yarrow, achillée millefeuille
(winter)
Russian knapweed, centaurée de Russie
(F&M)
Russian knapweed, centaurée de Russie
Russian knapweed, centaurée de Russie
(flower, enlarged)
Russian knapweed, centaurée de Russie
white snakeroot, eupatoire rugueuse white snakeroot, eupatoire rugueuse
common ragweed, petite herbe à poux common ragweed, petite herbe à poux
common ragweed, petite herbe à poux common ragweed, petite herbe à poux
(many inflorescences)
common ragweed, petite herbe à poux
(along edge of road)
common ragweed, petite herbe à poux
(along edge of road)
common ragweed, petite herbe à poux
(seedling, FF)
common ragweed, petite herbe à poux
(NC)
common ragweed, petite herbe à poux (racemes of inconspicuous male flowers, close up; the source of wind-borne pollen that is one of the main causes of hay fever)
common ragweed, petite herbe à poux and perennial ragweed, herb à poux vivace
(F&M)
perennial ragweed, herb à poux vivace
perennial ragweed, herbe à poux vivace perennial ragweed, herbe à poux vivace
(shoots from underground rootstocks)
giant ragweed, grande herbe à poux giant ragweed, grande herbe à poux
giant ragweed, grande herbe à poux giant ragweed, grande herbe à poux
(herbarium specimen)
giant ragweed, grande herbe à poux
(flowering inflorescences)
giant ragweed, grande herbe à poux
(flowering inflorescences)
giant ragweed, grande herbe à poux
(flowering inflorescences)
giant ragweed, grande herbe à poux
(seedling, FF)
giant ragweed, grande herbe à poux
(seedling, FF)
giant ragweed, grande herbe à poux (NC)
stinking mayweed, camomille des chiens stinking mayweed, camomille des chiens (NC)
common burdock, petite bardane common burdock, petite bardane
common burdock, petite bardane common burdock, petite bardane
(winter)
common burdock, petite bardane
(rosette)
common burdock, petite bardane
(seedling)
common burdock, petite bardane
(seedling)
woolly burdock, bardane tomenteuse
absinth, armoise absinthe absinth, armoise absinthe
(herbarium specimen)
absinth, armoise absinthe
(F&M)
biennial wormwood, armoise bisannuelle
(4 plants)
biennial wormwood, armoise bisannuelle
(2 plants)
mugwort, armoise vulgaire mugwort, armoise vulgaire
(herbarium specimen)
mugwort, armoise vulgaire
(herbarium specimen)
New England aster, aster de Nouvelle-Angleterre
New England aster, aster de Nouvelle-Angleterre New England aster, aster de Nouvelle-Angleterre
New England aster, aster de Nouvelle-Angleterre New England aster, aster de Nouvelle-Angleterre
New England aster, aster de Nouvelle-Angleterre New England aster, aster de Nouvelle-Angleterre
New England aster, aster de Nouvelle-Angleterre
(pink-and blue-flowered plants together)
New England aster, aster de Nouvelle-Angleterre
(blue flower)
nodding beggarticks, bident penché
nodding beggarticks, bident penché
nodding beggarticks, bident penché
nodding beggarticks, bident penché
nodding beggarticks, bident penché
(two heads with mature seed)
nodding beggarticks, bident penché
(five two-barbed seeds)
tall beggarticks, bident vulgaire
tall beggarticks, bident vulgaire
tall beggarticks, bident vulgaire
tall beggarticks, bident vulgaire
(close up)
tall beggarticks, bident vulgaire
(with mature two-barbed seeds)
tall beggarticks, bident vulgaire
(two-barbed seeds enlarged)
plumeless thistle, chardon épineux
(flower heads)
plumeless thistle, chardon épineux
(close up)
plumeless thistle, chardon épineux plumeless thistle, chardon épineux
nodding thistle, chardon penché
(eastern variety)
nodding thistle, chardon penché
(eastern variety)
nodding thistle, chardon penché
(western variety)
nodding thistle, chardon penché
(2 seedlings)
diffuse knapweed, centaurée diffuse brown knapweed, centaurée jacée
spotted knapweed, centaurée maculée black knapweed, centaurée noire
black knapweed, centaurée noire diffuse knapweed (upper left); spotted knapweed (upper right); black knapweed (lower left); brown knapweed (lower right).
A, flower head; B, bract of head; C, leaf; D, seed. (from C. Frankton and G. A. Mulligan 1987, Weeds of Canada, Publication 948, Agriculture Canada, Ottawa, Ontario, 217 pp.)
chicory, chicorée sauvage chicory, chicorée sauvage
chicory, chicorée sauvage chicory, chicorée sauvage
chicory, chicorée sauvage (NC) Canada thistle, chardon des champs
(flower heads)
Canada thistle, chardon des champs
(fruiting heads)
Canada thistle, chardon des champs
Canada thistle, chardon des champs Canada thistle, chardon des champs
Canada thistle, chardon des champs
(seedling, FF)
Canada thistle, chardon des champs (NC)
bull thistle, chardon vulgaire bull thistle, chardon vulgaire
bull thistle, chardon vulgaire bull thistle, chardon vulgaire
(3 rosettes)
bull thistle, chardon vulgaire
(seedling)
Canada fleabane, vergerette du Canada
Canada fleabane, vergerette du Canada
(herbarium specimens)
Canada fleabane, vergerette du Canada
(seedling)
Canada fleabane, vergerette du Canada (NC) smooth hawk's-beard, crépis capillaire
narrow-leaved hawk's-beard, crépis des toits
(photo by Stephen J. Darbyshire)
narrow-leaved hawk's-beard, crépis des toits
(photo by Stephen J. Darbyshire)
narrow-leaved hawk's-beard, crépis des toits
(herbarium specimen)
Philadelphia fleabane, vergerette de Philadelphie
Philadelphia fleabane, vergerette de Philadelphie Philadelphia fleabane, vergerette de Philadelphie
rough fleabane, vergerette rude rough fleabane, vergerette rude
spotted Joe-Pye weed, eupatoire maculée
(plants)
spotted Joe-Pye weed, eupatoire maculée
(in flower)
spotted Joe-Pye weed, eupatoire maculée
(maturing flower head)
hairy galinsoga, galinsoga cilié hairy galinsoga, galinsoga cilié
(F&M)
hairy galinsoga, galinsoga cilié hairy galinsoga, galinsoga cilié
(seedling)
orange hawkweed, épervière orangée orange hawkweed, épervière orangée (NC)
mouse-eared hawkweed, épervière piloselle king devil hawkweed, épervière des Florentins
spotted cat's-ear, porcelle enracinée elecampane, inule aunée
elecampane, inule aunée
(flower and fruiting head)
elecampane, inule aunée
(flowering head)
povertyweed, ive à fleurs axillaires povertyweed, ive à fleurs axillaires
(shoots from underground rootstocks)
povertyweed, ive à fleurs axillaires
(NC)
povertyweed, ive à fleurs axillaires
(F&M)
false ragweed, ive à feuilles de lampourde
(F&M)
false ragweed, ive à feuilles de lampourde
false ragweed, ive à feuilles de lampourde
(seedling)
prickly lettuce, laitue scariole
prickly lettuce, laitue scariole prickly lettuce, laitue scariole
prickly lettuce, laitue scariole (NC) blue lettuce, laitue bleue
blue lettuce, laitue bleue blue lettuce, laitue bleue
(herbarium specimen)
blue lettuce, laitue bleue (NC) nipplewort, lapsane commune
(cotyledons and first true leaf)
nipplewort, lapsane commune
(seedling)
nipplewort, lapsane commune
(plants)
nipplewort, lapsane commune
(seeds)
fall hawkbit, liondent d’automne
fall hawkbit, liondent d’automne fall hawkbit, liondent d’automne
(herbarium specimen)
fall hawkbit, liondent d’automne (NC) ox-eye daisy, marguerite blanche
ox-eye daisy, marguerite blanche ox-eye daisy, marguerite blanche
ox-eye daisy, marguerite blanche
(seedling, FF)
pineapple weed, matricaire odorante
pineapple weed, matricaire odorante pineapple weed, matricaire odorante
scentless chamomile, matricaire inodore scentless chamomile, matricaire inodore
scentless chamomile, matricaire inodore, stinking mayweed, camomille des chiens and pineapple weed, matricaire odorante
(F&M)
black-eyed Susan, rudbeckie hérissée black-eyed Susan, rudbeckie hérissée
black-eyed Susan, rudbeckie hérissée black-eyed Susan, rudbeckie hérissée (NC)
tansy ragwort, séneçon jacobée tansy ragwort, séneçon jacobée (NC)
Canada goldenrod, verge d’or du Canada. Canada goldenrod, verge d’or du Canada.
Canada goldenrod, verge d’or du Canada. Canada goldenrod, verge d’or du Canada.
(in field)
perennial sow-thistle, laiteron des champs perennial sow-thistle, laiteron des champs
(F&M)
perennial sow-thistle, laiteron des champs
(lacking glandular hairs)
perennial sow-thistle, laiteron des champs
(with glandular hairs)
perennial sow-thistle, laiteron des champs
(seedling, FF)
spiny annual sow-thistle, laiteron rude and annual sow-thistle, laiteron potager
(F&M)
spiny annual sow-thistle, laiteron rude spiny annual sow-thistle, laiteron rude
(flowers & fruit)
spiny annual sow-thistle, laiteron rude spiny annual sow-thistle, laiteron rude
(seedling, FF)
annual sow-thistle, laiteron potager annual sow-thistle, laiteron potager
annual sow-thistle, laiteron potager annual sow-thistle, laiteron potager
(flower)
annual sow-thistle, laiteron potager
(seedling)
dandelion, pissenlit officinal dandelion, pissenlit officinal
dandelion, pissenlit officinal
(in fruit)
dandelion, pissenlit officinal
(in field)
tansy, tanaisie vulgare tansy, tanaisie vulgare
goat's-beard, salsifis majeur
(flower)
goat's-beard, salsifis majeur
goat's-beard, salsifis majeur goat's-beard, salsifis majeur
(2 seedlings)
meadow goat's-beard, salsifis des prés
(flower)
meadow goat's-beard, salsifis des prés
colt’s-foot, tussilage pas-d’âne
(early flowering stage)
colt’s-foot, tussilage pas-d’âne
(patch in early flowering stage)
colt’s-foot, tussilage pas-d’âne
(later leaf stage)
colt’s-foot, tussilage pas-d’âne
(lower surface of leaf)
colt’s-foot, tussilage pas-d’âne
(patch in later leaf stage)
cocklebur, lampourde glouteron
cocklebur, lampourde glouteron