Distinguishing Ragweed and Goldenrod

Distinguishing Ragweed and Goldenrod

Stuffy nose—check.  Itchy eyes—check. Scratchy throat—check.  Looks like ragweed season has arrived.  Allergic rhinitis to ragweed pollen is common in the Kingston region, with many people suffering from symptoms such as those above at this time of the year.  The physical appearance of the culprit responsible, however, is frequently confused with another common flowering plant in the area.

Often seen growing by the roadside, in fields, and in backyards, the wildflower goldenrod is often erroneously blamed for ragweed-triggered allergies.  Both plants bloom at the same time—late August and early September— and are regularly found growing next to each other in similar environments.  Side by side, goldenrod is more noticeable due to its yellow colour, therefore individuals often associate it with their allergy symptoms.

Though they look somewhat similar goldenrod and ragweed species can be differentiated.  Once correctly identified, you can take the proper steps to minimize ragweed exposure by removing its presence around your home—mowing, hoeing, and hand pulling can be used to control the shallow-rooted plant—without pulling all of the goldenrod out of your yard.

Flowers

The most distinguishing feature of goldenrod is its bright golden yellow flowers when in bloom. The flowers generally grow in bunches on single stems. In contrast, ragweed’s flowers are green and more inconspicuous, growing in smaller formations on branched stems.

Foliage

If the plants have not yet flowered, differences in the plants’ foliage can also be used to discriminate them. The leaves of goldenrod are smooth and unlobed. Conversely, ragweed leaves are smooth, but deeply divided into lobes.  As well, ragweed stems are hairy, rough, and purple-green in colour, whereas those of goldenrod are smooth and green.

Pollen

Both ragweed and goldenrod produce copious amounts of pollen when they bloom in the late summer. The properties of their pollens, as well as how they are dispersed, differ significantly. The pollen produced by goldenrod is larger and is sticky compared to that of ragweed. The pollen adheres to the surface of pollinator insects such as bees, attracted to the flowers for their nectar. Thus goldenrod uses pollinators as its primary pollen dispersal mechanism.  Conversely, ragweed pollen is smaller and lighter than goldenrod pollen.  As such it is designed to stay aloft in the air and is primarily dispersed by wind.  Consequently, it is inhaled in the air we breathe, triggering allergic reactions in the upper airway of those with allergic rhinitis and causing recognizable itchy watery eyes and nasal symptoms.

In summary, a quick trick to distinguish the two plants: goldenrod has “gold” flowers and ragweed and “rag”eddy leaves.

 

References:

University of Florida Institute of Food and Agricultural Services Extension, Ragweed vs. Goldenrod handout, available at http://baker.ifas.ufl.edu/Horticulture/documents/Ragweedvs.Goldenrod.pdf.

eHow Plant Basics, What is the Difference Between Goldenrod and Ragweed article, available at http://www.ehow.com/info_8599702_difference-between-goldenrod-ragweed.html.

Oklahoma Gardening, Ragweed & Goldenrod video, available at https://www.youtube.com/watch?v=MZIcA41ET1o.