WHO KNEW Goldenrods are Essential for Biodiversity?

‘Keystone’ species are those that balance the diversity of an eco-system.

You’ve heard about wolves as a ‘keystone' species in the animal world, how their reintroduction helped restore vegetation in Yellowstone National Park after too-numerous elk and deer had over-browsed the plants there. But there are categories of ‘keystone’ species in the plant world too.

Entomologist Doug Tallamy has observed that in the plant world, trees are the most important for insects. Oaks are at the top of the list, hosting larvae of 473 insect species. Among American herbaceous plants, goldenrods are the most important, as they host 125 insects – more than any other herbaceous family. Not native to Europe, goldenrod is considered a weed, as there are no native insects to feed on them. Other ‘keystone’ families of herbaceous plants are asters, sunflowers and coneflowers.

This fall, fields and roadsides sport tall, handsome yellow goldenrods in full bloom, and most varieties will bloom for a long time. Their pollen is a major source of energy for late season native bees, and some bees require goldenrod pollen to feed their larvae. While the plants are falsely blamed for seasonal allergies the actual cause is rag-weed, a shorter and less attractive plant near roadsides; the pollen of goldenrods is too heavy to be airborne. There are about 100 types of goldenrod in the United States, about 30 of them are found in New England according to the Native Plant Trust in MA. The plants are not particular about soil and water, but some goldenrods are more aggressive than others. Gardeners who wish to help reverse the decline of insect species can pick well-behaved goldenrod varieties (genus Solidago) that can be grown from seed or divisions. Here are two good choices: blue stem (S. caesia) and zig zag (S. flexicaulis) are both shade tolerant and fairly short.