Thomas J. Elpel's
Web World Portal


Wildflower Logo.
Wildflowers & Weeds

Facebook Button.
Banner Image.
Wildflowers-and-Weeds.com  
Plant Identification, Edible Plants, Weed Ecology, Mushrooms, and more.
Home | Plant Identification | Plant Families Gallery | Edible Plants | Mushrooms | Links
Desertification & Weed Ecology | Profiles of Invasive Weeds | E-Mail | Search this Site

Asteraceae or Compositae: Aster or Sunflower Family Plant Identification Characteristics.

Asteraceae
Aster or Sunflower Family

(also known as the Composite Family: Compositae)

Key Words: Composite Flowers in disk-like heads

      The uniqueness of the Aster or Sunflower family is that what first seems to be a single large flower is actually a composite of many smaller flowers. Look closely at a sunflower in bloom, and you can see that there are hundreds of little flowers growing on a disk, each producing just one seed. Each "disk flower" has 5 tiny petals fused together, plus 5 stamens fused around a pistil with antennae-like stigmas. Look closely at the big "petals" that ring the outside of the flower head, and you will see that each petal is also a flower, called a "ray flower," with it's petals fused together and hanging to one side. Plants of the Aster family will have either disk flowers, ray flowers, or both. When the seeds are ripe and fall away, you are left with a pitted disk that looks strikingly like a little garden plot where all the tiny flowers were planted.

      The flower head is typically wrapped in green sepal-like "bracts" (modified leaves) surrounding the disk. The true sepals (found around individual flowers) have been reduced to small scales, or often transformed into a hairy "pappus", or sometimes eliminated altogether.

      One of the best clues for identifying members of this family is to look for the presence of multiple layers of bracts beneath the flowers. In an artichoke, for instance, those are the scale-like pieces we pull off and eat. Most members of this family do not have quite that many bracts, but there are frequently two or more rows. This is not a foolproof test, only a common pattern of the Aster family. Next, look inside the flower head for the presence of the little disk and ray flowers. Even the common yarrow, with its tiny flower heads, usually has a dozen or more nearly microscopic flowers inside each head, and the inside of a sagebrush flower head is even smaller. Keep in mind that many members of this family have no obvious outer ring of petals, including sagebrush.

      The Asters are the largest family of flowering plants in the northern latitudes, with 920 genera and 19,000 species found worldwide, including 346 genera and 2,687 species in the U.S. and Canada. Only the Orchid family is larger, but it is mostly restricted to the tropics.

      Many flowers from the Aster family are cultivated as ornamentals, including Marigold, Chrysanthemum, Calendula, and Zinnia. Surprisingly few are cultivated as food plants other than lettuce, artichoke, endive, plus the seeds and oil of the sunflower.

      The Aster family includes many subfamilies, only a few of which are native to North America. The Chicory/Dandelion subfamily and Aster subfamily have long been recognized by taxonomists. The Thistle and Mutisia subfamilies were formerly classified as tribes withn the Aster subfamily, but recently reclassified and promoted as subfamilies themselves. Check each of the subfamilies below for the best match to your specimen.

North American Subfamilies of the Aster Family
Click on the links below to see photos and learn more about each subfamily of the Aster family.

Chicory / Dandelion Subfamily | Thistle / Artichoke Subfamily | Aster Subfamily

There are more
Aster Family pictures
at PlantSystematics.org.

-Learning Plants by Families Article-
Return to Introduction


Botany in a Day: The Patterns Method of Plant Identification
Check out Botany in a Day

Return to the Plant Families Index

Return to the Wildflowers & Weeds Home Page

Books
authored by
Thomas J. Elpel
Roadmap to Reality: Consciousness, Worldviews, andthe Blossoming of Human Spirit
Roadmap
to Reality
Living Homes: Stone Masonry, Log, and Strawbale Construction
Living
Homes
Participating in Nature: Wilderness Survival and Primitive Living Skills.
Participating
in Nature
Foraging the Mountain West: Gourmet Edible Plants, Mushrooms, and Meat.
Foraging the
Mountain West
Botany in a Day: The Patterns Method of Plant Identification
Botany
in a Day
Shanleya's Quest: A Botany Adventure for Kids
Shanleya's
Quest

Portal Icon.
Return to Thomas J. Elpel's
Web World Portal | Web World Tunnel

Thomas J. Elpel's Web World Pages
About Tom | Green University®, LLC
HOPS Press, LLC | Dirt Cheap Builder Books
Primitive Living Skills | Sustainable Living Skills
Wildflowers & Weeds | Jefferson River Canoe Trail
Roadmap To Reality | What's New?

© 1997 - 2015 Thomas J. Elpel