Goldenrod mistakenly blamed for summer allergies

  • Goldenrod’s bright buds need pollinators to reproduce. Courtesy of Ruth Smith

  • Ragweed —Courtesy of Ruth Smith

For the Monitor
Published: 8/3/2018 2:06:27 PM

At this time of year, I often hear people say, “The goldenrod is in bloom and my allergies are acting up.” Those two things may happen at the same time, but not because goldenrod is the cause of late summer or fall allergies.

Goldenrod grows in a wide variety of places and is easily noticed because of its clusters of bright yellow flowers on tall stalks. That is in contrast to the rather inconspicuous ragweed, which can grow in similar places but has small greenish flowers, on short stems. Ragweed flowers don’t need to be showy because the plant is not trying to attract pollinators. It has very lightweight, wind-dispersed pollen. It’s that pollen which floats around in the air and can be inhaled by people that causes irritations and allergic reactions.

Aside from being misidentified as the source of seasonal sneezes, goldenrod is a plant with many fascinating characteristics. There are more than 100 species of goldenrod. Most are native to North America and about 25 species can be found in New England. They grow in habitats that range from seashores and swamps to open woods and dry fields.

In addition to being found in a wide variety of habitats, the many species of goldenrod also come in multiple shapes and sizes. For example, the common Canada Goldenrod, found growing in fields and along roadsides, has narrow, lance-shaped leaves that are sharply toothed. In contrast, the Stiff Goldenrod has leaves that are oval or oblong and rough. The flower heads also vary. The flower head of the Stiff Goldenrod is flat-topped, while the Canada Goldenrod bloom is more like a plume.

With so many different species, hybridizing is common and therefore specific identification can be difficult. Some ways that the plants avoid hybridizing is to blossom at different times so that they don’t cross-pollinate. Thus, the goldenrods which bloom in July or early August are different species from those that bloom in September or October.

As a member of the composite or daisy family, the flower heads are made up of many tiny flowers clustered together. By examining these flowers with a magnifying glass, you will see that there are made up of two types of flowers. The petal-like ray florets surround a center of circular disc florets. The ray florets have only female parts while the disc florets have both male and female parts. This allows for visiting insects to deposit pollen that they have collected from other flowers onto the female parts along the edge. As they work their way into the center of the flower, they will pick up sticky pollen from the male parts which then can be transferred to other flowers as they forage through the patch of goldenrod.

These sunny clusters of flowers not only add color to the landscape but provide food and shelter for countless species of invertebrates. Honey bees, bumblebees and flies feed on the nectar. Pollen provides food for bees and beetles. Predatory insects and spiders, such as the crab spider, in turn, pounce on the herbivorous insects. Birds visit and pick off insects to add a link to the goldenrod food chain. The leaves and stems provide food and shelter to various species of gall-producing flies, moths and midges.

The flowers ultimately produce clusters of tiny wind-borne seeds with soft hairs that aid in their dispersal. When seeds land in the soil, a new plant will sprout in the spring. Though a perennial, it does not bloom in the first year. It will bloom in its second year, put on vegetative heft above ground and begin to develop a network of rhizomes in the soil. The following spring, these rhizomes will each sprout a new stem. This continues over time, creating a massive clump of stems which are clones and can cover large areas and last for years.

The life history of these wildflowers and the animals that depend on them provides a counterpoint to their familiarity. There is a lot going on with goldenrod that is mostly unnoticed. Taking a closer look at these common neighbors will help us understand that they are not to blame for seasonal allergies and appreciate that they are more than sprays of color along the roadside.

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