A lot of folks don’t seem to like attempting to identify plants in the Asteraceae family, more commonly known as the asters. This is a very large family of plants and there are definitely many difficult cases out there in terms of identifying. However, with a good dichotomous key, a hand lens and some patience, I think most anyone can have success in learning some of these interesting plants. The key is learning what characteristics are “key.” The group I am featuring here are three members of the Symphyotrichum genus, often referred to as the “new world asters.” Following recent taxonomic revisions, the genus now holds more than 100 species, of which about 25 can be found in Missouri. Most ray flowers are light blue to violet but some can be white or pink as well.
Photographs can be useful when attempting to identify the new world asters. These can be referred to when attempting identification on your own or sending to someone with more expertise on the group. Knowing what to photograph is important.
First, both sides of the flower, referred to as the capitulum (composite inflorescence) in the asters, is important in making an identification. Photograph the ray and disk florets along with the involucre from the underside should be photographed. The involucre is a protective structure composed of a group of phyllaries (bracts) that can be beneficial in discerning between species. Asters in this group can be distinguished from one another by the number of ray florets per capitulum and the size of the flowerheads
Two other photographs you will want to take when attempting to ID the Symphyotrichum are of the plant’s growth habit and the leaves – particularly details of how the leaves are attached to the stems. There are usually key differences here that will be useful when making an identification. Unfortunately, I neglected to take closeups of the leaves while working with these three plants in the front yard this past autumn.
The next species I would like to feature is the spectacular Symphyotrichum oblongifolium, or “aromatic aster.” These plants are quite impressive. Pinch them back once sometime in the month of June and they will bush out, forming impressive globes of violet blooms. The accompanying habit photos are from our front bed and is only three plants! Although these plants create enormous amounts of blooms, I find that it is almost too late in the year. Most of the blooms don’t open until well into October. During this time, most of the pollinators that visited these blooms were honey bees, at least in my yard. I think most of the native pollinators had finished their season by this point.
The above images show the growth habit at flowering of Symphyotrichum oblongifolium.
I hope the next couple of images exemplifies how the phyllaries are important diagnostically for identifying these plants whose flowers look very similar when viewed head-on.
The capitulum of Symphyotrichum oblongifolium. Notice how strikingly different the involucre is compared to S. pattens.
Finally, the third member of this genus I have tried in the front yard beds is Symphyotrichum drummondii (Drummond’s aster). This one looks a lot different from the other two, not only in the characteristics of the capitulum, but in its growth habit as well. This is much more of a small, dainty plant that is found in open woodlands and savannahs in the northern sections of Missouri.
Anyone who has hung around biologists and naturalists long enough has surely heard the complaints of how taxonomists are going too far in their evil over-splitting ways. Their notion being that phylogenies painstakingly developed via decades of phenotypic comparisons should not be overturned by a few afternoons of running gels in a lab. I’m sure most of us can point to a convincing example of over-splitting amongst our favorite groups of organisms, but I hope that the subject that I am featuring tonight will give you pause before reaching for that familiar defense and realize there are circumstances where a group benefits from a fine dissection when the appropriate tools are available.
A great example of a group that has benefited from a well-executed genetic taxonomic treatment is the Spiranthes cernua species complex of the “ladies tresses” orchids. This species complex has long been known for cryptic species with curious cases of plants being plants – exhibiting hybridism, polyploidy (having more than two sets of chromosomes) and apomixis (reproduction without fertilization). The species, Spiranthes cernua, which is found in Missouri, has been problematic and considered as a polyphyletic taxa (derived from two or more distinct ancestral taxa). In attempting to shed light on the phylogenetics of this species complex, Mathew Pace and Kenneth Cameron have published a fantastic treatment in which they attempt at “Untangling the Gordian Knot”. Most of what I write here is paraphrased from their paper cited at the end of this post.
A common method of speciation in plants is interspecific hybridization. Pace and Cameron identified three instances of ancient hybrid speciation involving S. cernua. One of these circumstances that has now been given specific status is Spiranthes niklasii. This species is near-endemic to the Ouachita Mountains of Arkansas and is likely a result of a proposed ancient hybridization event between Spiranthes cernua and Spiranthes ovalis.
Pace and Cameron describe S. niklasii as being quite similar in appearance to S. cernua, but can be distinguished by “a central ridge of small papillae on the adaxial surface of the labellum, more strongly campanulate flowers, and usual preference for a more xeric habitat.” When I read this and found out we had an opportunity to see this species, I knew I wanted to try and capture those papillae in a photograph. We found this species in bloom in Saline and Pulaski Counties in Arkansas on 10, October, 2021. While my photos cannot do justice to the excellent figures found in the above mentioned work, I was still thrilled to be able to capture these minute structures while on a camping trip in the Ouachitas.
By the way, one of the other cases of hybrid speciation involving S. cernua that was identified by Pace and Cameron has further implications on my work. Spiranthes incurva is a newly described species that is hypothesized to be the result of an ancient hybridization between Spiranthes cernua and Spiranthes magnicamporum. In Missouri, the result of this split is that S. incurva now lies roughly above the Missouri River while S. cernua is found south of the river. This means that I now have added another species to my orchids of Missouri. A new orchid for me to photograph!
I would like to thank Casey Galvin and Eric Hunt for helping me find these plants.
Pace, Mathew C., and Cameron, Kenneth M. 2017. The systematics of Spiranthes cernua species complex (Orchidaceae): Untangling the Gordian Knot. Systematic Botany. 42(4): pp. 1-30
Until next time,
One day I would love to know how many of our moths received their common names. So many of them are interesting and perfect, like this, the sweetheart underwing (Catocala amatrix). In this case, the Latin binomial agrees. Catocala referring to the namesake, hidden underwing and amatrix meaning lover.
This moth was found in Franklin County, MO.
I’m never really fortunate enough to get a good image with their hindwings exposed, but here is a glimpse of the beauty they keep hidden, apparently useful for startling would-be predators upon their taking flight.
It’s been a while since I shared some, so here you go…
We found this cocoon of a parasitoid wasp (Ichneumonidae) during a WGNSS Nature Photo Group Outing in September of last year. This distinctive cocoon is identified to belong to a member of the subfamily Campopleginae who are characterized as koinobiont (allows host to continue development) endoparasitoids that primarily parasitize lepidopteran hosts. We did not find any remains of a potential host nearby.