Asteraceae (Compositae)

The Asteraceae are herbs, shrubs, or less commonly trees and are arguably the largest family of flowering plants, comprising about 1,100 genera and 20,000 species that are characterized by having the flowers reduced and organized into an involucrate pseudanthium in the form of a head or capitulum. The leaves are alternate, opposite, or less commonly whorled, and range from simple to pinnately or palmately compound; stipules are absent. Subtending and often partly enclosing the florets of the head is one or more series of usually green, free or variously connate bracts called involucral bracts or phyllaries. Another kind of bract called a receptacular bract or chaff may be associated with each disk floret throughout the head. The flowers are of two basic types: those with tubular actinomorphic corollas and those with strap-shaped or radiate zygomorphic corollas, often within the same head. Either type may be bisexual or unisexual. Where both types are found in a single head, the central flowers have tubular, usually 4-5- lobed corollas, and generally are bisexual, and the peripheral flowers have strap-shaped corollas generally with 3 distal teeth, and are usually female. Sometimes the heads lack ray flowers and are said to be discoid, consisting of only bisexual florets with tubular corollas. So-called disciform heads have bisexual central disk flowers surrounded by female flowers that have a very slender tube and an extremely suppressed or obsolete ligule. Ligulate heads consist only of bisexual florets with corollas of the ligulate or strap-shaped type but with generally 5 rather than 3 distal teeth. In another variation some or all of the florets in the head have 2-lipped corollas. In all cases the calyx is absent or so highly modified as hairs, bristles or scales on the ovary summit that it is given the alternative name of pappus. The corolla is sympetalous with mostly 3-5 lobes. The androecium nearly always consists of 4 or 5 stamens that are united by their anthers and are adnate to the corolla tube or epigynous zone, alternate with the lobes. The gynoecium consists of a single compound pistil of 2 carpels, a single 2-cleft style, and an inferior ovary with one locule and one basal ovule. During maturation of a flower, the style grows through the anther column, and as it does, hairs on the outer surface of the closed style lobes brush the pollen that is released into the anther column to the distal opening where it is available for biotic pollinators. A nectary in the form of a scale or small cup is commonly found alongside or around the base of the style. The fruit is an achene (cypsela) which may have a persistent pappus that commonly functions in fruit dispersal.

See Systematics, Evolution, and Biogeography of Compositae, Funk et al. 2009

Tribe Heliantheae

Tribe Cichorieae

Tribe Senecioneae

Miscellaneous Tribes (Alphabetically)

Each "thumbnail" image below is linked to a larger photograph.

Achillea millefolium, yarrow (Anthemideae). Aromatic foliage is one of the characteristics of this tribe which includes chrysanthemums and sagebrush.
Artemisia australis, Hawaiian endemic (Anthemideae).
Artemisia sp., wormwood, sagebrush (Anthemideae).
Matricaria discoidea, pineapple weed, (Anthemideae) Corvallis, OR.
Santolina chamaecyparissus, lavender cotton, (Anthemideae), OSU campus, Corvallis, OR, Jul 2004.
Gazania sp. (Arctotidae). This commonly cultivated garden plant represents one of the smaller tribes.
Baccharis pilularis, coyote bush, (Astereae), 1,2 - female; 3,4 - male.  Hatfield Marine Science Center, OR, Oct, 2005.
Chrysothamnus nauseosus, rabbit brush, (Astereae), Haines, OR, July, 2003.
Conyza canadensis, horseweed, horsetail, (Astereae), Corvallis, OR, Nov 2, 2005.
Monoptilon bellioides, desert star (Astereae), vic. Saguaro Natl. Park, AZ, Mar. 2004.
Solidago missouriensis, goldenrod (Astereae).
Tetramolopium filiforme (Astereae). Such notable plants as asters and goldenrods are in the same tribe as this attractive Hawaiian endemic.
Osteospermum sp. (Calenduleae). This lesser tribe is here represented by a popular ground cover. Butterflies and skippers commonly visit the flowers of this family. Their proboscis is well suited to siphon the small quantities of nectar from the small tubular flowers.
Arctium minus, common burdock, (Cardueae), MacDonald-Dunn Forest, Oak Creek Trail, OR, July, 2003.
Centaurea sp. (Cardueae),  OSU Campus, Corvallis, OR, July 2003.
cir_vuls.jpg (10755 bytes) Cirsium vulgare, bull thistle (Cardueae).  Note the long, linear corolla lobes and the spine-tipped involucral bracts.
Cynara scolymus, artichoke (Cardueae).
Echinops sp. (Cardueae). This species is in the thistle tribe along with such notables as artichokes. Members of this tribe often have prickly foliage and bracts. Another feature of the tribe that this photo shows is the long linear lobes of the disk flowers. This particular species is further distinguished by presentation of flowers in a head of heads. Each of the heads is reduced to a single disk floret with subtending involucral bracts and these simplified heads are in turn arranged in a compact head.
Chaenactis cf. carphoclinia, pebble pincushion (Chaenactideae), vic. Saguaro Natl. Park, AZ, Mar. 2004.
Bidens amplectens, koko'olau (Coreopsideae). This Hawaiian endemic species is another typical member of the Heliantheae tribe, although the receptacular bracts aren't obvious in this photo. A common weed, Bidens pilosa, has some populations with discoid heads and others with radiate heads.
Bidens pilosa, beggars tick (Coreopsideae). The highly modified calyx or pappus as it is called in this family in this species takes the form of two or three barbed awns at the tip of each ovary. These very effectively increase dispersal of the fruits by mammals and birds.
Fitchia speciosa (Coreopsideae). Tantalus, O'ahu, 2005. The deeply cleft zygomorphic disk corollas are unusual for Heliantheae.
Ageratum conyzoides (Eupatorieae). This species has cultivated and weedy forms. Characteristics of the tribe include heads with only tubular corollas that are never yellow.
Ageratina riparia, spreading mist flower (Eupatorieae).
Liatris sp. (Eupatorieae), OSU Campus, Corvallis, OR, July, 2003.
mik_scas.jpg (11310 bytes) Mikania scandens (Eupatorieae).  A vine from Madagascar.
Anaphalis margaritacea, pearly everlasting (Gnaphalieae), 1,2 - Hackleman Old Growth Trail, Cascades, OR, July 2003; 3 - Mt. Seymour, B.C., Canada.
Antennaria alpina alpine everlasting (Gnaphalieae). 
Gnaphalium sandwicensium, straw flower (Gnaphalieae). This tribe typically has herbage with dense, white woolly hairs and heads with papery bracts that persist when dry. This native Hawaiian species shows these features rather nicely.
Gaillardia aristata, blanket flower (Helenieae). Note the peripheral involucral bracts and 3-notched ray florets, and central disk florets (first photo). In the second photo, the fruits are shattering from the mature head. Each achene has a crown of bristle-tipped scales that represents the modified calyx or pappus. Close attention to the receptacle will reveal the presence of bristly receptacular setae interpreted as enations rather than chaff scales.
Gaillardia sp. (Helenieae), OSU Campus, Corvallis, OR, July, 2003.
Helenium autumnale, sneezeweed, (Helenieae), OSU campus, Corvallis, OR, July, 2003.
Pluchea indica and P. Symphytifolia (1) F1 hybrid (2,3) (Inuleae) Ka'ena Point, O'ahu.
Argyroxiphium sandwicense ssp. macrocephalum, Haleakala silversword (Madieae). The well-known Hawaiian silversword evolved from members of the subtribe Madiinae that are found on the west coast of North America. Adaptive Radiation of the Hawaiian Silversword Alliance
Madia sativa, coast tarweed (Madieae), vic. Corvallis, OR, July, 2003.

More about tarweeds (Subtribe Madiinae)

esp_schs.jpg (14705 bytes) Espeletia schultzii (Millerieae), high elevation rosette plants from the Andes, Venezuela.  Some members of this genus have a vegetative habit strikingly similar to the silverswords of Hawai'i (see above).
Galinsoga quadriradiata, shaggy soldier (Millerieae). Manoa Valley, Oahu, Jan, 2000.
Tridax procumbens, coat buttons(Millerieae). The heads on the left have a series of green involucral bracts or phyllaries enclosing two kinds of florets. The 3-notched white corollas at the periphery belong to the zygomorphic female ray flowers. The more numerous yellowish perfect, tubular, actinomorphic flowers in the center are called disk flowers. Each of them has an associated receptacular bract or chaff scale that is not readily visible unless the head is dissected or until it matures and sheds its fruits as is the case with the head on the right. Two achenes (cypsellas) with highly modified calyx (pappus) of pectinate bristles are also visible.
Adenocaulon bicolor, pathfinder (Mutisieae), Hackleman Old Growth Trail, Cascades, OR, July 2003.
Trixis californica (Mutisieae). This tribe, which includes the commonly cultivated genus Gerbera, is characterized by having some or all of the florets of the head bilabiate or 2-lipped.
Lycoseris crocata (Mutisieae).
tag_min_mids.jpg (8355 bytes) Tagetes minuta (Tageteae).  This tribe consists largely of foetid, often insecticidal herbs, including the cultivated marigolds.
Tagetes lucida, Spanish, Mexican, or Texas tarragon, Mexican mint marigold (Tageteae).  Nursery trade, cultivated, O'ahu.
Cyanthillium cinereum, little or Asian ironweed, purple fleabane (Vernonieae), alien weed, Hawai'i.
Hesperomannia arbuscula (Vernonieae). This is a rare Hawaiian endemic genus.

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