Asteraceae

The largest or second largest plant family in the world, and in New Brunswick, with species occurring in almost every imaginable habitat from terrestrial to aquatic. New Brunswick species are mostly non-woody (herbaceous), includes food plants (e.g. Sunflower), ornamentals (e.g. Marigold, Dahlia, Zinnia), many weeds (e.g., Ragweed), showy native or introduced plants (e.g. Black-eyed Susan), and several Aster species that are endemic and at risk (e.g., Gulf-of-St. Lawrence Aster). Plants are most easily identified during late bloom, when both flowers and fruit are present and can be examined in detail.

Individual flowers or florets often small, inconspicuous, and aggregated, often densely, into composite heads, each functioning as and superficially appearing to be a single flower but actually consisting of dozens to hundreds of flowers compacted together. The flower heads may be composed entirely of small tubular disk flowers, each symmetric in all directions (radially), entirely of bilaterally symmetric elongate petal-like ray flowers that may be tongue-like, or one- to two-lipped and are only tubular at the base, or a mixture of both. Where both are present, disk flowers form a central disk and the ray flowers surrounding the disk like rays of the sun (e.g. Daisy). Individual flowers or florets may be bisexual or unisexual, or sometimes sterile. The flower heads may occur in clusters, in patterns resembling cymes or racemes. Sepals lacking or highly modified into a pappus that consists of 2 to many persistent, often fused, scales or awns, a series of bristles, or a ring of tissue surrounding the fused petals at their base or occurring on the summit of the fruit. If present, the tuft of hairs is most obvious and easily studied after the fruit has developed. Petals 5, fused, the ray flowers with 3 to 5 lobes or teeth. Stamens usually 5, their stalks (filaments) attached to the petal tube and their tips (anthers) fused and forming a tube around the style. Carpels 2, fused, ovary located below the point of attachment of the other flower parts (inferior). A nectary is at the tip of the ovary. Each head is surrounded by 4 to many bracts (phyllaries) arranged in one or more rings and collectively forming the involucre, and the florets that form the head are inserted onto an expanded or swollen structure (receptacle) at the top of the stem or its branches. Bristles or scales (chaff) may or may not be on the receptacle among the flowers. Fruit an achene, often crowned by hairs, and sometimes flattened, winged or spiny.

Leaves alternate and spiral, opposite or whorled, simple to deeply lobed or dissected, entire to variously-toothed. Stipules lacking.

Plants in this family store carbohydrates as simple sugars, may produce resins or latex, and usually contain aromatic oils (terpenes).