Asteraceae

Flower:

• Head of many (composite) small sessile (not stalked) flowers (florets)
• Florets perfect
• Aggregated (clustered) on common receptacle
• Surrounded by involucral bracts
• Outermost florets mature first, center ones last ( indeterminate )

• Ray florets:
  • Corolla tubular only at base; expanded upward into prominent ligule
  • No stamens, floret is functionally pistillate
• Disk florets:
  • Regular, tubular corolla
  • Usually normal and perfect
• Ligule florets:
  • Corolla expanded to one side in a ligule
• Flower heads composed only of ligulate florets are ligulate heads
• Flower heads composed only disk florets are discoid heads
• Flower heads composed only disk florets in center and ray florets around margin are radiate heads
• Heads are single or in a panicle or corymb

radiate head	ligulate head	discoid head

This animation will help to depict the different flowers that compose the inflorescences of the plants in the Asteraceae family. After viewing this animation, you should have a better understanding of the differences between ligulate, discoid and ray flowers.

Fruit:

• Achene—dry, indehiscent (not splitting open) capsule

 Form:
Annual, perennial, or biennial herbs and occasionally shrubs.
A basal rosette is often formed at the base of the plant (daisy) but leaves may (coneflower) or may not (rudbeckia) be present on the stem.

basal rosette		coneflower (Echinacea)

Leaves:

• Type: simple, rarely compound
• Arrangement: alternate, opposite, rarely whorled. Leaves sometimes opposite below and alternate above. Exstipulate (no stipules)
• Margins: various, entire to toothed, dissected, occasionally compound

Stems:
Stems maybe hollow or solid and contain a milky white sap. Stems may also be prickly or pubescent.

Roots:
Roots may be found near the surface (daisy) or a deep taproot (dandelion.)