In northeastern North America, there are a few species of goldenrod that conspicuously inhabit old farm fields, including Canada goldenrod, tall goldenrod, rough-leaved goldenrod, giant goldenrod, and early goldenrod. But there are many others. In my town, gray goldenrod (Solidago nemoralis), sharp-leaved goldenrod (Solidago arguta), and downy goldenrod (Solidago puberula) are three that are more common than one might think, but just not everywhere.
I’ve mentioned these species before, and I’ve even posted pictures of S. arguta earlier in the growing season, when it was just getting going. Sharp-leaved goldenrod is blooming now, but the only places I find it are along heavily-shaded dirt roads. Maybe that’s why some people call it forest goldenrod. The plants are tall, but the leaves are more widely placed on the stem than any species living in the open sun (except early goldenrod). My guess is that they don’t have the resources to make lots of leaves, so they spread them out in hopes of catching as many sun flecks as possible during the day. And they minimize one leaf shading another. They don’t produce a lot of flowers, but enough that you would notice them when you drive at a speed appropriate for a poorly-graded road.
Gray goldenrod is short, maybe half the height of the species that dominate old fields. I used six different fields in my research back in the 1970s, and in only one of them did gray goldenrod account for more than one percent of the plant cover. In Iowa, Patricia Warner and Robert Platt found gray goldenrod on the driest soils they studied. Massachusetts is not as dry as Iowa, but there are dry places here and there where the taller species might have trouble making a living. Those are places where gray goldenrod can maintain a foothold. One such place is in just a bit too steep to mow next to a field not far from one of our elementary schools. About 50 meters from a mesic slope covered with tall and Canada goldenrod, gray goldenrod is holding forth, blooming beautifully, with only grasses to cast shadows on their leaves.
Downy goldenrod used to be abundant behind our house when it was a field with small pine trees. Now those pines are several meters tall, casting too much shade for sun-loving goldenrods. Our neighbors sold off some timber about 25 years ago, and the open area by the road was another place for downy goldenrod, at least up until a few years ago. I checked last week and the birches have grown tall, too tall, it seems, for the goldenrods. I couldn’t find any.
But along the highway to the north, the west roadside has some downy goldenrods, and on the opposite side, with a sparsely-wooded wetland next to it, there is a thriving stand. They tend to be taller than gray goldenrod, but shorter than Canada goldenrod. They do best on nutrient-poor soil (reduced competition?), and many roadsides qualify for that distinction. Good to see some, compact and bright, finishing off the summer.
If a goldenrod looks a little different from what you expect, or is in a place that seems unusual, then it is probably not one of the more common species. These glimpses of something different are the first clue to the diversity of goldenrods. It’s a good time of year to appreciate how many kinds there are.