
Asteraceae (ass-ter-AY-see-ee)
Iconic Features
- Composite heads of many flowers
- Disk and/or straplike flowers
Description (Jepson)
- Eudicotyledons (eudicots) – a major lineage of flowering plants including most plants traditionally described as dicots and generally characterized by
- 2 seed leaves (dicotyledon)
- Netted (reticulate) leaf venation
- Flower parts in fours and fives
- Pollen grains with 3 pores (tricolpate)
- Vascular bundles in stem arranged in a ring
- Taproot system
- Mostly annuals and herbaceous perennials
- Also can be shrubs, vines, and trees
- Leaves
- Simple (not divided into leaflets) to compound (divided into leaflets)
- Basal and/or cauline (on the stem)
- Alternate (1 leaf at each junction with stem) or opposite (2 leaves at each junction with stem) or, rarely, whorled (3 or more leaves at each junction with stem)
- Flowers
- Inflorescence (flower arrangement) is in densely packed heads (capitulum/a) of dozens to hundreds of individual flowers
- Heads may appear singly or in a variety of secondary arrangements
- Flowerheads come in 4 basic forms (with many variations)
- Radiate Heads have both disk and ray flowers (e.g. mule’s ears)
- 5-lobed star- or tube-shaped disk flowers cluster in the center
- 3-lobed strap-like ray flowers rim the edge
- Ligulate (Liguliflorous) Heads have only 5-lobed, strap-like flowers (e.g. dandelion)
- Discoid Heads have only 5-lobed star- or tube-shaped disk flowers (e.g. mugwort)
- Disciform Heads have disk and disk-like flowers (e.g. everlasting)
- 5-lobed star- or tube-shaped disk flowers cluster in the center
- Disk-like flowers with minute or missing rays rim the edge
- Radiate Heads have both disk and ray flowers (e.g. mule’s ears)
- Flowers are protandrous (male flower parts mature before female parts) and employ a strategy of secondary pollen presentation
- Anthers (pollen-producing part of the stamen/male structure) are fused into a column facing toward and surrounding the pistil (female flower part)
- When still immature, the style (pistil stalk) elongates, pushing ripe pollen up through the anther column to present to pollinators
- When the flower’s own pollen is depleted, the style splits to receive pollen from other flowers
- This strategy is believed to reduce the chance of self-pollination
- Sepals (protective covering for bud) are absent or modified into a pappus, composed of bristles or scales (e.g. the tufts of a dandelion seed)
- Ovary inferior (below the attachment of other flower parts)
- Composite head is usually held in a whorl of bracts (modified leaves), called an involucre
- Individual bract is called a phyllary
- Phyllaries (pattern, shape, ranks, etc.) is often diagnostic
- Individual flowers lack stems; instead they are attached to a platform called a receptacle
- Inflorescence (flower arrangement) is in densely packed heads (capitulum/a) of dozens to hundreds of individual flowers
- Fruit is an achene (a single-seeded, dry fruit that does not split open), often with pappus attached to aid dispersal

Notes
- Approximately 23,000 species worldwide, in many habitats
- Largest family of vascular plants in California (Jepson eFlora) and of eudicots globally
- Found everywhere except Antarctica and the extreme Arctic
- Great variety of horticultural, economic, and medicinal uses
- Scientific name from the included genus Aster, from the Greek for “star”
- An early name for this family was Compositae because what appears to be an individual flower is actually a composite of flowers, as in a bouquet
- Other common names are the Daisy or Composite family
- Due to its size, the Sunflower family is traditionally broken into a number of subgroups, including tribes; here are some tribes and representative plants
- Mayweed Tribe (Anthemideae) – yarrow (Achillea millefolium), sagebrush (Artemisia species), pineapple weed (Chamomilla sauveolens)
- Aster Tribe (Astereae) – asters (Aster species), gumplants (Grindelia species), coyote brush (Baccharis pilularis)
- Chicory Tribe (Cichorieae) – California dandelion (Agoseris grandiflora), hawkweeds (Hieracium species), silver puffs (Uropappus lindleyi)
- Thistle Tribe (Cynareae) – star-thistles (Centaurea species), Italian thistle (Carduus pycnocephalus)
- Sunflower Tribe (Heliantheae) – mule ears (Wyethia species), tarweeds (Madia species), goldfields (Lasthenia species)
- Everlasting Tribe (Inuleae) – cudweed (Pseudognaphalium californicum), stinkwort (Dittrichia graveolens)
- Represented by 94 species at Edgewood
Specific References
Candeias, M. 2019, Sep. 22. An intriguing way of presenting one’s pollen. In Defense of Plants.
Mason, J. 2004. [Sunflower family flower-head illustrations, adapted]. In T. Corelli, Flowering Plants of Edgewood Natural Preserve (2nd. ed.). Monocot Press, Half Moon Bay, California. (c) CC BY NC 3.0.
Browse Some Edgewood Plants in this Family












