Asteraceae – Aster Family

After Orchids, the Aster Family is one of the largest family of flowering plants. Over 1528 genera and 22,750 species globally and more than 2,600 in North America alone.[i] Many within the Asteraceae are cultivated for their horticultural benefits (Marigolds, Zinnias, Black-eyed Susans, Cosmos) or their herbal or edible qualities (Sunflowers, Echinacea, Chamomile, Artichokes, Endives, Artichokes, and Lettuces).

Although seemingly uncomplicated, Asters are complex with what looks like a single blossom actually being comprised of hundreds of individual, miniscule flowers. This characteristic therefore gave this group its old family name, “compositae.”[ii] Most plant families discussed in this work have floral parts in a predictable order: sepals encapsulating petals. Petals that surround stamens. Stamens that whorl around female reproductive parts in the center. The Aster family, however_,is very different and imagining the face of a sunflower can help illustrate these complexities.

On any average Sunflower, what appear to be green sepals are actually modified leaves, or bracts, often appearing in multiple layers on the receptacle. Carefully placed petals give the appearance of there being only one large flower, but look closely at the middle of the blossom and one discovers hundreds of minuscule, individual flowers clustered together. Called disk flowers, each of these has their their own microscopic sepals, petals, and reproductive parts – which matures into an individual sunflower seed. Even those showy petals are individual flowers under careful examination. These ray flowers have a single long petal and often lack stamens or pistils, rendering them infertile.[iii] All members of the Asteraceae have either disk flowers, ray flowers, or both.

Among the Asters, true sepals are reduced to small scales, or a hairy pappus, or sometimes eliminated all-together. One of the key clues to identifying members of the Aster family is to look for the presence of multiple layers of false sepals (actually bracts) beneath the flowers. In an artichoke, for example, 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, such as with the back of the common dandelion. This is not a fool-proof test, only a semi-predictable pattern. Or, if inside each flower head, one finds many smaller flowers contained within. As with Yarrow and its many tiny blossoms arranged in a corymb – even these tiny flowers contains yet many more smaller blooms.[iv]

Achillea millefolium – Common Yarrow

Species Code: ACMI

Habit: Rhizomatous, aromatic, perennial forb.

Leaves: Leaves are lance shaped in outline, but pinnately dissected and fern or feather like, ranging from ¼ – 1 ¼” wide x 1 ¼ – 6” long.[v] Alternately arranged and evenly distributed along the stem, leaves closer to the ground are largest with variable degrees of hairiness, or pubescence.[vi]

Stems: Erect, generally simple, somewhat hairy, ranging from 10-100 cm tall.[vii]

Flowers: In the Willamette Valley, petals are generally white and occasionally pink, cultivars can range from yellow to salmon in color.[viii] heads are small arranged in a terminal flat-toped corymb inflorescence. Heads have approximately 3-8 tiny ray flowers.[ix]

Seeds: Flowers produce numerous smooth, flattened achenes. Very small, 1-2 mm long and pale in color, becoming somewhat gray when mature.[x]

Ecology: Facultative Upland Species (FACU), persists in dry uplands and wet prairies.[xi]

Notes: Lacey leaves, dense/flat inflorescence, and distinctive aroma make this species easy to identify. However, can sometimes be confused with young Daucus carota (Queen Anne’s Lace) in the field. Different Yarrows have been used for medicinal purposes throughout history across cultures and continents due to its astringent, diuretic, and diaphoretic properties[xii]. In the Pacific Northwest it was used by various peoples for sore throats, colds, coughs, anti-diarrheal, and even during childbirth to aid in expelling the placenta.[xiii] The plant’s Latin name, Achillea, originates from Greek mythology when the warrior Achilles reportedly used yarrow’s to stop soldiers’ bleeding during the Trojan War.[xiv]