As August gives way to September, roadsides, field borders and fencerows begin to light up with bright yellow flowers. At the same quickness that these late summer flowers bloom, comments start rolling in about seasonal allergies.

Goldenrod is everywhere during late summer and early fall. It is bright, noticeable and appears at exactly the same time many people begin sneezing, dealing with itchy eyes and reaching for allergy medication. However, despite decades of accusations, goldenrod is usually not the cause of those miserable late summer and early fall allergy symptoms. The real culprit is often growing right beside it. Ragweed, not goldenrod, is responsible for the vast majority of late-summer and early-fall pollen allergies.

Goldenrod is one of Ohio's most recognizable native wildflowers. Depending on the species, it can grow several feet tall and produce dense clusters of bright yellow blooms. These blooms can be found along roadsides, in old fields, pastures, conservation areas and crop field edges across much of the state.

Because it is so visible, goldenrod tends to get blamed whenever allergy season arrives. Ragweed, on the other hand, is far less noticeable. Its flowers are small, green and easy to overlook. Most people walk by ragweed every day without realizing what it is or even noticing that it is flowering.

The difference between these two plants comes down to how they reproduce. Goldenrod relies on insects for pollination. Bees, butterflies and many other beneficial insects visit goldenrod flowers to collect pollen and nectar. Because insects are doing the work, goldenrod produces pollen that is relatively heavy and sticky. The pollen is designed to cling to insects, not float freely through the air. As a result, very little goldenrod pollen becomes airborne. In most situations, people are unlikely to inhale enough goldenrod pollen to trigger allergy symptoms.

Ragweed has developed a completely different strategy. Rather than relying on insects, ragweed depends on the wind to carry its pollen from one plant to another. That means ragweed must produce tremendous amounts of lightweight pollen capable of traveling through the air. A single ragweed plant can release millions, even billions, of pollen grains during a growing season. These tiny pollen particles can be carried long distances by wind currents and are easily inhaled by people who are sensitive to them.

Goldenrod deserves far more appreciation than it usually receives. In fact, many ecologists consider native goldenrods among the most valuable late-season plants. Ohio is home to numerous (25) native goldenrod species, including tall goldenrod (S. altissima), showy goldenrod (S. speciosa), stiff goldenrod (S. rigida), gray goldenrod (S. nemoralis), and blue-stemmed goldenrod (S. caesia). While many people simply see a patch of yellow flowers, these plants function as important ecological hubs supporting a tremendous diversity of insects.

During late summer and early fall, goldenrod provides pollen and nectar at a time when many other flowering plants have already finished blooming. Honeybees, bumble bees, mining bees, sweat bees, leafcutter bees, and numerous other native bee species can often be found actively foraging on goldenrod blooms. Butterflies such as monarchs, painted ladies, pearl crescents, and various skipper species also regularly visit goldenrod flowers.

The ecological value of goldenrod extends well beyond pollination. Research has documented more than 100 insect species that depend upon goldenrod for at least part of their life cycle. Some insects are so closely associated with goldenrod that they are rarely found on other plants.

One of the most recognizable examples is the goldenrod gall fly (Eurosta solidaginis). This small fly lays eggs in goldenrod stems, causing the plant to produce a distinctive round gall. Those galls become miniature ecosystems, providing food and shelter for numerous insects and serving as winter food sources for birds such as chickadees and downy woodpeckers.

Goldenrod also hosts numerous beneficial insects that support agricultural and horticultural systems. Adult hover flies, also known as syrphid flies, frequently feed on goldenrod nectar and pollen. Their larvae are voracious predators of aphids and other soft-bodied pests. Lacewings, parasitic wasps, minute pirate bugs, lady beetles, and many other natural enemies commonly utilize goldenrod resources while helping suppress pest populations in nearby crop fields, gardens, and landscapes.

From an integrated pest management perspective, flowering plants such as goldenrod can serve as valuable insectary plants. By providing food resources for beneficial insects, they help support biological control services throughout the growing season. Many of the predators and parasitoids that aid in managing aphids, caterpillars, and other crop pests require nectar or pollen at some point in their life cycle. In other words, those bright yellow flowers lining roadsides and field edges are doing far more than decorating the landscape. They help feed pollinators, sustain beneficial insects, support wildlife, and contribute to biodiversity.

Of course, it is possible for an individual to have a specific sensitivity to almost any plant. Direct contact with goldenrod may cause irritation for some people. However, when discussing widespread seasonal allergies that affect millions of Americans each year, ragweed is overwhelmingly the primary offender.

So the next time you drive past a field glowing with golden-yellow flowers while reaching for another tissue, remember that the bright blooms are probably not the plant making you miserable. Goldenrod may simply be guilty of being highly visible at the scene of the crime. The real culprit is likely the ragweed hiding nearby, quietly releasing clouds of pollen into the late-summer air.

Frank Becker is the Agriculture and Natural Resources Extension Educator with Ohio State University Extension – Wayne County, and a Certified Crop Adviser, and may be reached at 330-264-8722 or becker.587@osu.edu
CFAES provides research and related educational programs to clientele on a nondiscriminatory basis. For more information, visit cfaes.osu.edu/nondiscrimination
This article was previously published in The Daily Record.