OPINION

Naturally Speaking Yellow Composites

Steve Lekwa

Prairies, woodland edges and roadsides can become of sea of yellow in late summer. There are still some blue flowers like asters and lavender flowers like blazing stars and tick trefoils out there, but you have to keep a sharp eye out to see them among the dominant tall waving yellow-flowered plants. Most of the yellows fall into an unofficial plant group known to botanists as “darn yellow composites,” or DYCs for short. Composite flowers are actually two kinds flowers in a single head, composed of a central disk section that will bear the seeds and an outer ring of ray flowers that appear more like petals. DYCs can be so similar that sorting them out to species can be a challenge.

Multiple species of DYCs bloom across Iowa from spring to fall, but three genera of plants dominate the DYC group on uplands in central Iowa in late summer. They include three Silphiums that are at or just beyond their peak blooming period; at least seven Solidagos (goldenrods), and five Helianthus (sunflowers). A couple of species of Bidens (tickseeds), and Sneezeweed add splashes of gold to wetland edges.

Each of the three Silphiums have different-shaped leaves, but all are thick and rough in texture. They are often the tallest flowers around. Compass plant has large deeply lobed leaves that tend to orient in a north-south direction. Cup plant has large leaves forming a cup that entirely encircles the stems. Rosinweed is the third member of this genus, but has more normal looking leaves. The flowers are carried high above the leaves on stout stems.

Solidagos (goldenrods) have over 60 species across the country and most are coming into full bloom now. Members of this group occupy nearly all habitat niches including wetlands, woods, prairies and even highly disturbed “waste areas.” Their flower heads are composed of bunches of tiny composite flowers that form graceful plumes, clubs, wands and flat-topped clusters, depending on the species. Leaf shapes run from narrow and grass-like to large and rough. I have identified seven species of goldenrods in Story County, alone, and probably have missed at least a couple of more obscure ones.

The genus Helianthus (sunflowers) also forms a large, diverse group that occupy a variety of habitats. Most, as you might expect, stay out in the sun. A few grow in semi-shaded woodlands, as well. They include the weedy annual common sunflower, but the rest are perennial natives. All produce seeds that are rich in oils and are important bird foods from late summer through the winter.

Bidens (tickseeds) like wet soil and don’t get very tall. Anyone who has visited a wetland in the fall will recognize their barbed seeds that stick like masses of ticks to any passing fabric or fur. Some ducks eat the seeds. Sneezeweeds are taller moist soil plants that look like they might be a kind of sunflower. Because they are insect pollinated, they probably didn’t get their unusual name because they make people sneeze. Wind pollinated ragweeds are the main culprits for late summer sneezes.

The composites are important sources of nectar and pollen for insects, including butterflies and bees. Many produce important wildlife food, and a few even produce foods that people can eat. Just as important for most people, though, is their ability to paint our roadsides and field edges bright golden yellow in late summer.