Asteraceae (=Compositae)


"Sunflower Family"



Dicot

 

Flower Characteristics Representatives
Vegetative Characteristics Images
Other Points of Interest Links

 

Flower Characteristics
  • inflorescence or few to many flowers borne in a head (=capitulum)
  • individual flowers are often called "florets" and are of 2 types:
  • 1)  disc flowers
    • regular and epigynous
    • no sepals as we know them, but a calyx of fluffy bristles called a pappus
    • tubular corolla of 5 lobes
    • stamens 5, epipetalous with the anthers connate
    • pistil with  inferior ovary of 2 carpels, but ovules reduced to 1, 1 locule, stigma branched and curved
    • floral formula: Asteraceae floral formula -achene
  • 2)  ray flowers
    • identical to disc flowers except the tubular corolla is expanded on one side into a long petal lobe making the flower irregular
    • floral formula: Asteraceae floral formula -achene (but frequently sterile in radiate heads)
  • heads of three types:
    • 1) discoid heads: only disc flowers (e.g. Antennaria)
    • 2) ligulate heads: only ray flowers (e.g. Taraxacum, Cichorium, Lactuca)
    • 3) radiate heads: both ray and disc flowers (e.g. Senecio, Helianthus)
Vegetative Characteristics
  • mostly herbs, a few shrubs (and a few tropical trees)
  • leaves simple or comound; margins entire, toothed, lobed, etc.; alternate but in some opposite or even whorled 
Other Points of Interest
  • the largest dicot family with 950 genera and 20,000 species
  • distributed all over the earth and in almost all habitats
  • food plants include lettuce, globe artichoke, endive, salsify, and chicory
  • pollen of ragweed (Ambrosia)causes allergic reaction in some humans
  • many weeds
  • many used as ornamentals: strawflower, shasta daisy, english daisy, marigolds, zinnia
Representatives
  • Sunflower (Helianthus)
  • Goldenrod (Solidago)
  • Lettuce (Lactuca)
  • Aster  (Aster)
  • Ragweed (Ambrosia)
  • Marigold (Tagetes)
  • Blue Mink (Ageratum) 
Images
 
 

Links

 





Amaryllidaceae Cruciferae Lamiaceae Rosaceae
Apiaceae Cyperaceae Leguminosae Scrophulariaceae
Araceae Fabaceae Liliaceae Solanaceae
Asteraceae Fagaceae Magnoliaceae Umbelliferae
Brassicaceae Gramineae Orchidaceae Violaceae
Caryophyllaceae Iridaceae Poaceae  
Compositae Labiatae Ranunculaceae