Why is it that goldenrod and aster are seemingly always found adjacent to one another? Does it have anything to do with pollination? Is there some type of symbiosis?
Michael Petit, Portland
The spectrum of yellows, oranges, and red leaves across Maine’s deciduous forests in fall is nice, sure. But have you seen a native meadow in fall bloom?! The swaths of yellow goldenrods and asters in shades from pink to purple, with red winterberry berries bursting on the field’s edges, have a certain je ne sais quoi of natural beauty. Goldenrods and asters are both generally late-blooming flowers and provide many benefits to wildlife during their bloom and beyond.
The abundance of these flowers in late summer and fall leads to quite a few symbiotic relationships with a large diversity of insects and other animals. I should make the point that many people misassociate fall allergies with goldenrods, while the blame should instead be on ragweed (typically Ambrosia artemisiifolia). Ragweeds pollinate through wind dispersion, which is why people with hay fever allergies react to its pollen. Goldenrods, on the other hand, are insect-pollinated.
This dependence on insects is where a symbiosis comes in: for our late season pollinators like butterflies and bees, the abundance of goldenrods and asters means they have enough food (in the form of nectar) to put on reserves to survive the winter or to make the next leg of their migration south. For each species of flower, they ideally only want pollen (sperm) from a member of their same species; otherwise fertilization is unlikely. Of course cross-pollination can lead to hybrids, but those tend to be ecological dead ends, rather than beneficial for either species.
Goldenrods and asters are both very large groups of flowers. They are even pretty closely related, both being in the family asteraceae, and even ragweeds are in that large family. Being so diverse, you’ll see different species of either asters or goldenrods growing in a variety of habitats, often one near the other. Despite the close quarters, these are filling slightly different ecological niches, otherwise they’d outcompete one another. So while they may not be benefiting each other directly, the presence of one could help attract more pollinators, benefiting the other. No one has written more eloquently about this combination of beauty and science than Robin Wall Kimmerer in her book, Braiding Sweetgrass, where she explains that, in the eyes of a bee, goldenrods and asters appear very similar. “Growing together,” she says, “both receive more pollinator visits then they would if they were growing alone.” Together, their abundance is helping many critters, from monarchs fueling up on their migration to Mexico, queen bees looking for a last meal before spending the winter underground, or one of the dozens of gall-inducing insects that use goldenrods and asters.
Why do we, in Maine, sometimes get rare hummingbirds in the fall but not the spring?
Ariana van den Akker, Portland
Readers may recall my plea for Mainers to keep their hummingbird feeders up and stocked well into the fall in a September column. Almost all of our ruby-throated hummingbirds depart by the first week of October, though we occasionally see late stragglers. I’m especially interested in detecting western vagrants that rarely but predictably stray to the northeast in the fall. Many of the rare birds that show up in Maine occur during spring or fall migration, and while there are many theories and catalysts for vagrancy, the majority tend to be when birds are migrating. In spring, most of our rarities are southern overshoots—that is, they’ve literally flown too far north. During fall, we often see western vagrants, many of which are immature and presumably lost on their southern migrations.
One theory around vagrancy is that many are males prospecting for new territory. In the last few decades rufous hummingbirds have become increasingly recorded as vagrants, even overwintering in the southeastern United States, rather than their usual winter haunts of southern Mexico. It is fun to speculate that perhaps these birds wintering in the United States are finding their way back to the breeding grounds faster than before and are slowly evolving a new migration route.
Whatever the reason for their misguidance, your feeders could give a stray or lingering hummingbird the boost it needs to make the next jump on its journey. So get some fresh sugar water (4 parts water to 1 part sugar ratio) hung outside and let me know if you have any visitors this fall!
Do you have a nature question for Doug? Email questions to ask@maineaudubon.org and visit maineaudubon.org to learn more about virtual and backyard birding, online classes and other programs about wildlife and habitat.
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