3-9 Asteraceae, aster family
Keywords:
Magnoliophyte, aster family, dicots, composite flowers, yarrow, snakeroot, ragweed, pussytoes, pearly everlasting, chamomile, burdock, arnica, wormwood, lamb succory, daisy, beggar's ticks, thistle, knapweed, chicory, horseweed, coreopsis, brass-butAbstract
Worldwide, the aster relatives comprise a vast family, with around
20,000 species. Nearly 10% of Nova Scotia‘s flora consists of members
of this family, at 160 plus species of annual or perennial herbs.
Formerly known as the Compositae, that name best describes the flower
structure of the family. The ‘flowers‘ are actually composite clusters
of small florets upon a common receptacle. Some florets are disk
florets, individuals of a tubular form and forming a disk or button.
Other florets are ray florets, straplike in outline and tubular only
at the base; these have the appearance of petals, although each is
actually a functional flower.
Species may have only disks (discoid) or only rays (ligulate), or they
may have both (radiate) types of flowers within the heads. The florets
contain an inferior ovary producing an achene. The calyx is reduced to
a pappus which is an assemblage of scales, teeth or bristles. In some
cases, the pappus is absent.
The receptacle may be scaly or chaffy and may or may not be subtended
by an involucre.
Identification is made easier if both flowers and fruit are present.
To assist in separating the large numbers of species, several keys
follow, firstly based on the floret arrangements.Photographs provided
by Ross Hall, Martin Thomas, Sean Blaney, Marian Munro, Beth Cameron,
David Mazerolle, Jamie Ellison, Alain Belliveau, Andy Dean.