Pick up know-how for tackling diseases, pests and weeds.
Farm bill, farm marketing, agribusiness webinars, & farm policy.
Find tactics for healthy livestock and sound forages.
Scheduling and methods of irrigation.
Explore our Extension locations around the state.
Commercial row crop production in Arkansas.
Agriculture weed management resources.
Use virtual and real tools to improve critical calculations for farms and ranches.
Learn to ID forages and more.
Explore our research locations around the state.
Get the latest research results from our county agents.
Our programs include aquaculture, diagnostics, and energy conservation.
Keep our food, fiber and fuel supplies safe from disaster.
Private, Commercial & Non-commercial training and education.
Specialty crops including turfgrass, vegetables, fruits, and ornamentals.
Find educational resources and get youth engaged in agriculture.
Gaining garden smarts and sharing skills.
Timely tips for the Arkansas home gardener.
Creating beauty in and around the home.
Maintenance calendar, and best practices.
Coaxing the best produce from asparagus to zucchini.
What’s wrong with my plants? The clinic can help.
Featured trees, vines, shrubs and flowers.
Ask our experts plant, animal, or insect questions.
Enjoying the sweet fruits of your labor.
Herbs, native plants, & reference desk QA.
Growing together from youth to maturity.
Crapemyrtles, hydrangeas, hort glossary, and weed ID databases.
Get beekeeping, honey production, and class information.
Grow a pollinator-friendly garden.
Schedule these timely events on your gardening calendar.
Equipping individuals to lead organizations, communities, and regions.
Guiding communities and regions toward vibrant and sustainable futures.
Guiding entrepreneurs from concept to profit.
Position your business to compete for government contracts.
Find trends, opportunities and impacts.
Providing unbiased information to enable educated votes on critical issues.
Increase your knowledge of public issues & get involved.
Research-based connection to government and policy issues.
Support Arkansas local food initiatives.
Read about our efforts.
Preparing for and recovering from disasters.
Licensing for forestry and wildlife professionals.
Preserving water quality and quantity.
Cleaner air for healthier living.
Firewood & bioenergy resources.
Managing a complex forest ecosystem.
Read about nature across Arkansas and the U.S.
Learn to manage wildlife on your land.
Soil quality and its use here in Arkansas.
Learn to ID unwanted plant and animal visitors.
Timely updates from our specialists.
Eating right and staying healthy.
Ensuring safe meals.
Take charge of your well-being.
Cooking with Arkansas foods.
Making the most of your money.
Making sound choices for families and ourselves.
Nurturing our future.
Get tips for food, fitness, finance, and more!
Understanding aging and its effects.
Giving back to the community.
Managing safely when disaster strikes.
Listen to our latest episode!
Yellow Wildflowers Dominate in the Fall
One had better learn to like yellow wildflowers if you are on the prowl on Arkansas backroads in the fall. They are everywhere. Standing in large patches along the roadway or sometimes painting whole pastures with their cheery patches of yellow. Why all these yellow flowers?
While my windshield observations are completely unscientific, I would guess that about 80 percent of the wildflowers seen blooming along Arkansas roadways in the fall have yellow flowers. Sure, there are a few white blooming plants, and a few purples, but mostly they are yellow. Why all this yellow? As with most things we see in nature, the answer is complicated.
If you record the late summer and fall blooming species with yellow flowers – and there are more than a dozen widely distributed species – it is quickly apparent they are all in the daisy (Aster or composite) family. The daisy family has a wide spectrum of flower colors but yellow is the go-to color for most species. White, blue and orange are somewhat common but red is largely absent.
Among the most common fall composites are the Helianthus (sunflowers such as bristly, woodland, downy, sawtooth, annual, narrowleaf), Silphium (rosinweed, cup plant, prairie dock, compass plant), Rudbeckia (black-eyed Susans such as cutleaf, sweet coneflower), Bidens (tickseed sunflower) and Solidago (goldenrods such as tall, Canadian, showy, stiff, blue-stem, old field, woodland, and many others). The least amongst these plants will be three feet tall while some may grow to six or eight feet in height. They often occur in dense stands.
The aster family is mostly dominated by species that evolved to survive in open, sunny, often dry climates. The same kind of climate favored by grasses. Fossil records indicate that the daisy family appeared about the same time as the grasses; about the time dinosaurs went extinct. Many of the members of this enormous family coevolved with grasses in a prairie or savannah type habitat and are large, vigorous plants that are as tall as or taller than the surrounding grasses.
To attain this size, many of the members of the aster family in northern (or southern) temperate climates initiate flowers as the length of the days begin to get shorter after the summer solstice. Before that, they are making vegetative growth and attaining sufficient size to stay ahead of the grasses. These “short day plants” often require a couple months for flower buds to form after bud initiation is triggered in early July. In a typical year, yellow flowered members of the aster family dominate the roadsides from late-August through mid-October.
But why are members of the daisy family mostly yellow? The aster family, unlike grasses that adopted wind pollination, chose insect pollination. The human eye has three main types of color receptors in the eye; red, green and blue. We miss everything outside of the visible spectrum, which includes a lot of bandwidth. Bees have three types of photoreceptors but in their case, they are ultraviolet, blue and green. Butterflies have at least six light sensing cells, ranging from the ultraviolet to blue, green, red and into the near-red broadband spectrum.
When these yellow flowers are photographed with ultraviolet filters you see completely different color patterns. To us the ray petal of a sunflower looks uniformly yellow, but when seen as an insect would see it, they have a bullseye pattern with the basal end of the petal often highly saturated with violet shading. I could find no images of goldenrod flowers taken in the ultraviolet spectrum but I suspect they too look different to the insect eye.
Goldenrods begin blooming in mid-summer and, rotating through the more than 30 species found in the state, bloom until frost. They are often blamed for causing hay fever, but because they are insect pollinated with heavy, sticky pollen grains, they are innocent victims of prejudice. Ragweed, another member of the daisy family but one that evolved with wind pollination, is the culprit. It too is fall blooming, with its flowering time coinciding with the peak goldenrod season.
All of these fall blooming members of the aster family have an important role in the health of our ecosystem. Most of them produce oily seeds in great abundance. These are favorites of all the birds, especially those migrating through the region on their way south for the winter.
Gerald Klingaman is a retired Arkansas Extension Horticulturist and retired Operations Director for the Botanical Garden of the Ozarks. After more than two decades of penning the popular Plant of the Week column, he’s taking a new direction, offering views on nature as he pokes about the state and nation. Views and opinions reflect those of the author and are not those of the University of Arkansas System Division of Agriculture. If you have questions or comments for Dr. Klingaman about these articles contact him at musingsonnature@gmail.com.