Compositae - composite family
1600 Apeldoorn Ave., Ottawa, Ontario, Canada, K2C1V5 |
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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 knapweed, centaurée 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. Ambrosia artemisiifola L., common ragweed, petite herb 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, herb 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 herb 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. 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. 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. 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, tanaise 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 pres 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. 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.
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