Asteraceae

Plant Sex: Flowers bisexual or unisexual (plants monoecious).

Flowers: Two kinds of flowers: RAY - zygomorphic (ligulate = strap-shaped). DISK - actinomorphic (radiate = tubular). Stamens with free filaments but connate anthers. Filaments adnate to corolla tube. Gynoecium of two carpels with 1 locule, 1 ovule.

Inflorescence: A CAPITULUM (head) surrounded by bracts called PHYLLARIES.

Fruits: an achene from an inferior ovary, sometimes called a CYPSELLA.

Habit: Mostly herbaceous perennials; some shrubs and trees.

Leaves: Variable; alternate, opposite or whorled; rarely compound.

THE LARGEST FAMILY OF ANGIOSPERMS! Divided into 3 subfamilies and 17 tribes (see Table 9.4 in your text). These are based on features of the phyllaries, the pappus, and style branches, as well as whether heads have all ray flowers, all disk flowers, or both ray and disk. These three types will be given after the generic names as R, D and R&D.

Food
Cichorium (R)

C. intybus (chicory). Habit of plant in flower.

Cynara (R)

C. scolymus (artichoke). Habit of plant.

Helianthus (R&D)

H. annuus (sunflower). Habit of plant in flower. Close-up of the sunflower head. Disk flowers (of H. angustifolius). Fruits.

Lactuca (R)

L. sativa (garden lettuce). Field of cultivated lettuce.
L. floridana (woodland lettuce). A native species, showing the all radiate heads.

Ornamentals

Coreopsis (R&D)

C. basalis (coreopsis). Capitula.
C. gigantea. Habit of the TREES in California!

Gynura (D)

G. aurantiaca (purple passion vine). Habit of cultivated plant in flower.

Leucanthemum (R&D)

L. vulgare (chrysanthemum). Habit of plants in flower.

Senecio [Pseudogynoxys] (R&D)

S. cummingii. A cultivated plant in the SIUC greenhouse.

Tagetes (R&D)

T. erecta (= T. patula, French marigold). Habit of plant in flower.

Zinnia (R&D)

Z. angustifolia (zinnia). Capitula.
Z. elegans (zinnia). Plants in flower.

Wildflowers

Aster (R&D)

A. shortii (Short's aster). Flowering shoot. Capitulum in L.S. Dissection showing ray (top) and disk (bottom) flowers. Fruits.

Bidens (R&D)

B. aristosa (beggar-ticks). Flowering shoot. Capitulum.
Fruits of B. frondosa and B. bipinnata.

Echinacea (R&D)

E. pallida (pale coneflower). Habit of plants in flower. Capitulum. Capitulum L.S. Fruits.

Liatris (D)

L. aspera (rough blazing star). Inflorescence (a spike of capitula). Fruit.
L. pycnostachya (prairie blazing star). Habit of plant in flower. Inflorescence. Capitula. Disk flowers. Fruits.

Rudbeckia (R&D)

R. hirta (black-eyed Susan). Habit of plants in flower. Capitulum. Ray flowers. Disk flowers. Fruits.

Senecio (R&D). Huge genus undergoing revision; many segregate genera.

S. [Packera] glabellus (ragwort, groundsel). Habit of plant in flower. Capitula. Infructescence (of S. vulgaris).
Senecio sp. A woody species in cultivation in Mexico.

Silphium (R&D)

Prairie showing two species: S. terebinthinaceum (prairie dock) and S. laciniatum (compass plant).
S. perfoliatum (cup plant). Connate-perfoliate leaf bases that trap water and apparently keep insects away from the flowers. Capitulum. Capitulum L.S. Infructescences.

Solidago (R&D)

S. canadensis (goldenrod). Habit of plant in flower.
S. gigantea. Inflorescence. Closer view of capitula.

Vernonia (D)

V. missurica (ironweed). Habit of plant in flower. Capitula. Ray flowers. Disk flowers. Fruits.

Weeds
Ambrosia (perianth lacking)

A. trifida (giant ragweed). Leaves behind Pastinaca.
A. artemisiifolia (common ragweed). Habit of plant in flower.
A. bidentata (ragweed) Staminate inflorescences.

Circium (R)

C. discolor (thistle). Capitulum in L.S.
C. horidulum. The very spiny plant in flower.
C. sp. (thistle). Capitulum with crab spider. Ray flowers. Disk flowers. Fruits.

Conyza (D)

C. canadensis (horseweed). Capitula forming young fruits.

Eupatorium (D)

E. rugosum (white snakeroot). Habit of plant in flower.

Taraxacum (R)

T. officinale (dandelion). Developmental series from flower to fruit.

Tragopogon (R)

T. pratensis (goat's beard). Habit of plants in flower Capitulum. Capitulum. Capitulum L.S. Ray flowers. Infructescence.

Xanthium (perianth lacking)

X. strumarium (cocklebur). Habit of plant in fruit. Involucre encloses two flowers, later forming two chambers inside the bur with hooked prickles.
X. spinosum. A very spiny monoecious herb in an agricultural field in Spain.

SIUC / College of Science / Elements of Plant Systematics
URL: http://www.plantbiology.siu.edu/PLB304/Lecture23Apial/Asteraceae.html
Last updated: 29-Mar-08 / dln