Asteraceae: A Family Portrait


Asteraceae: A Family Portrait
  • Posted January 20, 2015
What do lettuce, artichokes, dandelions and sunflowers all have in common? They are four of the 27,773 species in the Asteraceae family, the largest botanical family in the world. The Asteraceae clan is comprised by the simple bright cheery flowers that make life a little lighter — species like daisies, chrysanthemums, coneflowers, marigolds, black-eyed Susans and the family’s namesake, asters .
black eyed susan coneflower Marigold
Black-eyed Susan Coneflower Marigold

Their smiling flowers make this family easy to love — and also easy to identify. Most species have some variation on the flower structure epitomized by sunflowers. The massive blooms of sunflowers are actually a composition of hundreds of tiny individual flowers, hence the older name for their family, Compositae. What looks like a ring of outer petals is actually a series of specialized flowers, called ray flowers. The middle of each sunflower is made up of numerous miniscule disk flowers.

sunflower

Many Asteraceae flowers exhibit heliotropism, tracking the sun across the sky each day by pivoting their flower heads to face it. People often associate this phenomenon with sunflowers, which always appear facing the same direction as if they are bunch of happy soldiers marching toward the sun. The truth, however, is that they don’t actually pivot throughout the day like so many other Asteraceae, they simply face the east in unison and stay that way.

field of sunflower

There’s much more to the Asteraceae family than the familiar faces that we find in almost every flowerbed. Among the 27,000 members are some truly exotic cousins, such as the Haleakala silversword. Unless you’re gardening above 7,000 feet in elevation in the alpine deserts on the slopes of one of Hawaii’s dormant volcanoes, you’ll have a hard time cultivating this plant. It grows slowly in the otherwise barren landscape of volcanic cinders to become a spiky ball of silver foliage about 20 inches in diameter. If all goes well, after about 50 years it sends up a single 6-foot flower stalk covered with deep maroon sunflower-like blossoms, sets seed and then promptly shrivels up and dies.

silversword silversword
Brian Barth
About the Author

After 15 years as a professional landscape designer and horticulturalist, Brian Barth embarked on a second career to share his passion—and the knowledge he's accrued—through writing. His love of plants is all-encompassing, but he has a particular soft spot for culinary crops.


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Asteraceae: A Family Portrait