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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 or 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 green things outside the flower head that might look like sepals are actually "bracts" (modified leaves) surrounding the disk. The true sepals 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 species of 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 consists of two subfamilies. The Dandelion subfamily includes a variety of plants with dandelion-like flowers. The ray flowers typically over-lap all the way to the center. The petals have strap-like, parallel edges with squared-off ends. The stems and leaves of all species have milky juice, and all are edible, but bitter. Bitter substances like dandelion greens are helpful as an appetizer to stimulate digestive secretions before the main meal. Eating your dandelions can help reduce problems with indigestion later. Keep in mind that there are many other plants with milky juice that are not related to Dandelions, including some that are poisonous. Be sure to check the blossoms for proof.

      The Aster subfamily is much larger, made up of eleven tribes, some of them radically different from the others. Thistles and knapweed are found in the Artichoke tribe.

      The Chamomile tribe includes the most aromatic members of the Aster family, such as sagebrush, yarrow, tansy, and of course, chamomile. As a kid I encountered many different species of sage (Artemisia). There are 19 species just in Montana. But without a patterns approach to go by, I didn't have a clue where to start, so I brought each specimen to the university herbarium for identification. These days, when I see a new fuzzy green-gray plant, I immediately crush a leaf and smell it to test for a sage-type smell. Each species smells different, but there is a common pattern to the smell that is undeniably sage-like.

      I also test for members of the Sunflower tribe by smell. Most species are resinous, much like pines, useful medicinally for their expectorant properties. Crush up the head of a sunflower and smell it to get a sense of the resin odor. Once you learn the patterns of smell from the various families, subfamilies and tribes, you will be able to accurately identify many new plants with just your nose.

Aster Family / Dandelion Subfamily

Aster Family / Aster Subfamily
Artichoke Tribe | Ragweed Tribe | Everlasting Tribe | Chamomile Tribe | Groundsel Tribe
Boneset Tribe | Sunflower Tribe | Sneezeweed Tribe | Aster Tribe

Please e-mail Thomas J. Elpel to report mistakes or to inquire about purchasing high resolution photos of these plants.


Dandelion Subfamily
Notice how the flowers and seedheads of each plant resembles the dandelion.

Taraxacum officinale. Common Dandelion. There are several species of native dandelions in North America, but the common dandelion found in most lawns is an import from Eurasia. I really like to eat dandelion greens and roots. For more information go to harvesting and eating dandelions.

Hypochaeris glabra. Smooth Cat's Ear.

Sonchus arvensis. Field Sowthistle.

Sonchus arvensis. Field Sowthistle.

Sonchus oleraceus. Common Sowthistle.

Sonchus oleraceus. Common Sowthistle.

Hieracium aurantiacum. Orange Hawkweed.

Hieracium aurantiacum. Orange Hawkweed.

Hieracium albiflorum. White-flowered Hawkweed.

Hieracium albiflorum. White-flowered Hawkweed.

Cichorium intybus. Common Chicory.

Crepis intermedia. Limestone Hawksbeard.

Tragopogon spp. Salsify. This plant is also known as "oyster plant" because the first-year roots have a taste that resembles oysters. This is a biennial plant that grows a root and basal leaves the first year, then sends up the flower stalk the second year and dies after setting seed.

Tragopogon spp. Salsify seedhead.

Agoseris aurantiaca. Mountain Dandelion.

Agoseris spp. False Dandelion.

-Also see these additional members of the Dandelion Subfamily-


Aster Subfamily
Artichoke Tribe
Notice how the flowerheads of each plant resemble little artichokes.

Centaurea maculosa.Spotted Knapweed. Spotted knapweed is an invasive weed imported from Eurasia. For more information go to spotted knapweed ecology and control.

Centaurea diffusa.Diffuse Knapweed. Diffuse knapweed is an invasive weed imported from Eurasia. For more information go to knapweed ecology and control.

Centaurea solstitialis.Yellow Star Thistle. Yellow star thistle (same genus as knapweed) is an invasive weed imported from Eurasia. For more information go to knapweed ecology and control.

Centaurea repens.Russian Knapweed. Russian knapweed is an invasive weed imported from Eurasia. For more information and additional pictures, go to Russian knapweed ecology and control.

Centaurea cyanus. Bachelor's Buttons.

Centaurea cyanus. Bachelor's Buttons. An introduced ornamental flower.

Cirsium arvense. Canada Thistle. Canada thistle is an imported invasive weed from Eurasia, not from Canada. For more information go to Canada thistle ecology and control..

Cirsium vulgare. Bull Thistle. Bull thistle is an imported invasive weed from Eurasia.

Carduus nutans Musk Thistle. Musk thistle is an imported invasive weed from Eurasia. For more information go to Musk thistle ecology and control.

Carduus nutans Musk Thistle..

Cirsium scariosum. Elk Thistle.

Cirsium scariosum. Elk Thistle. Elk thistle is a native plant usually found at high elevations.

Arctium minus. Lesser Burdock. An introduced weed with an edible taproot.

Arctium minus. Lesser Burdock.


Aster Subfamily
Ragweed Tribe
These are green-globby flowers that might resemble the Goosefoot family at first glance.

Iva xanthifolia. Giant sumpweed. It is often found growing in or around livestock pens.

Xanthium strumarium. Cocklebur. Grows along many western rivers.


Aster Subfamily
Everlasting Tribe
Notice how the flowerheads of each plant are wrapped in layers of colorful, papery bracts.

Antennaria spp. Pussytoes.

Anaphalis margaritacea. Pearly Everlasting.


Aster Subfamily
Chamomile Tribe
Most plants of this tribe are powerfully aromatic.

Artemisia tridentata. Big Sagebrush.

Artemisia tridentata. Big Sagebrush.

Artemisia tridentata. Big Sagebrush.

Artemisia frigida. Fringed Sagewort.

Artemisia cana. Silver Sagebrush.

Tanacetum vulgare. Common Tansy. Tansy is an imported invasive weed from Eurasia. For more information go to Tansy ecology and control..

Matricaria matricarioides. Pineapple Weed

Matricaria maritima.Scentless Chamomile. Rexburg, Idaho.

Achillea millefolium. Yarrow. .

Leucanthemum vulgare. (Same as Chrysanthemum leucanthemum.) Oxeye Daisy. Oxeye Daisy is an imported invasive weed from Eurasia. For more information go to Oxeye Daisy ecology and control..

-Also see these additional members of the Chamomile Tribe-


Aster Subfamily
Boneset Tribe

Brickellia eupatorioides.False boneset.

Brickellia eupatorioides. False boneset. Close-up.

Liatris punctata.Dotted Gayfeather.

Liatris punctata. Dotted Gayfeather. Close-up.


Aster Subfamily
Groundsel Tribe
These members of the Aster Family are distinguished by the especially soft and abundant pappus hairs within the flowerheads.

Arnica cordifoliaHeart-Leaved Arnica.

Arnica angustifolia. Alpine Arnica.

Senecio spp.Groundsel

Senecio spp. Groundsel.

Senecio triangularis.Arrow-leaved Groundsel.

Senecio triangularis Groundsel with moth, used with permission of Mountain Escapes Photography

-Also see these additional members of the Groundsel Tribe-

  • Senecio spp. Groundsel. Photographed along the northern California coast.
  • Senecio spp. Groundsel. Chatfield State Park. Denver, Colorado.
  • Senecio salignus. Willow Groundsel. Flowers give off a rotting smell to attract flies for pollination. Sonora Desert Museum. Tuscon, Arizona.
  • Senecio salignus. Willow Groundsel. Close-up.

Aster Subfamily
Sunflower Tribe
Many plants of the Sunflower Tribe have a distinctively resinous odor.

Balsamorhiza sagittata. Arrowleaf Balsam Root.

Balsamorhiza sagittata. Arrowleaf Balsam Root.

Helianthus annuus.Wild Sunflower.

Helianthus tuberosus. Jerusalem artichoke. Cultivated in our yard.

Helianthus nuttallii.Nuttall's Sunflower.

Helianthus nuttallii. Nuttall's Sunflower. Perennial.

Ratibida columnifera.Prairie Coneflower.

Ratibida columnifera. Prairie Coneflower.

Rudbeckia occidentalis.Western Rayless Coneflower. Photographed in the Bridger Mountains, near Bozeman, Montana.

Rudbeckia occidentalis.Western Rayless Coneflower.

Rudbeckia hirta. Blackeyed Susan.

Rudbeckia laciniata. Cutleaf Coneflower.

Madia gracilis. Slender Tarweed. Photographed near Twisp, Washington.

Enceliopsis argophylla. Silverleaf Sunray. Photographed at Lake Mead National Recreation Area.

Echinacea angustifolia. Narrow-leaved Purple Coneflower.

Coreopsis tinctoria. Golden Tickseed. Planted as a roadside flower near Boulder, Montana.

Wyethia helianthoides. Mule's Ears.

Wyethia helianthoides. Mule's Ears.

Bidens cernua. Nodding Beggartick.

Bidens tripartita. Threelobe Beggarticks.

-Also see these additional members of the Sunflower Tribe-

  • Rudbeckia laciniata. Cut-leaf Coneflower. Photographed along Montana's Smith River.
  • Encelia farinosa. Brittlebush. Sonora Desert Museum. Tuscon, Arizona.
  • Encelia farinosa. Brittlebush. Close-up. The fragrant resin is used as an incense and for glue and waterproofing. The sap doesn't melt in the sun.

Aster Subfamily
Sneezeweed Tribe

Gaillardia aristata. Blanket flower

Gaillardia aristata. Blanket flower.

Chaenactis alpina. Alpine Dusty Maiden

Tetraneuris grandiflora. (Formerly known as Hymenoxys grandiflora.) Alpine Sunflower.

Helenium autumnale. Common Sneezewed

Helenium autumnale. Common Sneezewed


Aster Subfamily
Aster Tribe

Solidago spp. Golden Rod. Lava Lake Trail. Near Bozeman, Montana.

Solidago spp. Golden Rod. Near Glacier National Park. Montana.

Heterotheca villosa. (Formerly known as Chrysopsis villosa.) Golden Aster.

Heterotheca villosa. (Formerly known as Chrysopsis villosa.) Golden Aster.

Grindelia squarrosa. Sticky Gum Plant. Common across the Rocky Mountains.

Grindelia squarrosa. Sticky Gum Plant. Photographed near Rexburg, Idaho.

Aster spp. Asters.

Aster spp. Alpine Aster.

-Also see these additional members of the Aster Tribe-

There are more
Aster Family pictures
at PlantSystematics.org.

-Learning Plants by Families Article-
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