Hairy White Oldfield Aster, Frost Aster, Hairy Aster, Awl-Aster, Michaelmas Daisy, Steelweed

Symphyotrichum pilosum

(Symphyotrichum pilosum var. pilosum)

sim-fy-oh-TRY-kum  pil-OH-sum

Synonyms of Symplyotrichum pilosum (2) (Updated on 12-4-23 from Plants of the World Online): Aster ericoides var. pilosus (Willd.) Porter, Aster pilosus Willd.
Synonyms of Symphyotrichum pilosum var. pilosum (9) (Updated on 12-4-23 from POWO): Aster chrysogonii Sennen, Aster ericoides var. platyphyllus Torr. & A.Gray, Aster ericoides f. villosus (Torr. & A.Gray) Voss, Aster ericoides var. villosus Torr. & A.Gray, Aster juniperinus E.S.Burgess, Aster pilosus var. demotus S.F.Blake, Aster pilosus var. platyphyllus S.F.Blake, Aster pilosus f. pulchellus Benke, Aster villosus Michx.

Symphyotrichum pilosum (Willd.) G.L.Nesom is the accepted scientific name for this species of Symphyotrichum. It was named and described as such by Guy L. Nesom on Phytologia in 1995. It was previously named and described as Aster pilosus by Carl Ludwig Willdenow in the fourth edition of Species Plantarum in 1803.

Accepted Infraspecific Names (2) (Updated on 12-4-23 from POWO): *Symphyotrichum pilosum var. pilosum (autonym), Symphyotrichum pilosum var. pringlei (A.Gray) G.L.Nesom. *When infraspecific taxon are named, an autonym (“type-specimen”) is automatically generated whose description is closest to the (original) species. All have their own list of synonyms… Symphyotrichum pilosum var. pilosum is found in Missouri where I live.

The genus, Symphyotrichum Nees, was named and described as such by Christian Gottfried Daniel Nees von Esenbeck in Genera et Species Asterearum in 1832.

As of 12-4-23 when this page was last updated, Plants of the World Online by Kew lists 100 species in the Symphyotrichum genus. It is a member of the plant family Asteraceae with 1,702 genera. Those numbers could change as updates are made on POWO.

The above distribution map for Symphyotrichum pilosum is from Plants of the World Online. Areas in green are where the species is native and purple where it has been introduced. The map on the USDA Plants Database is similar but also includes Texas and Louisiana. You can click on the links to view the subordinate taxa’s own maps. 

The map on iNaturalist shows where members have made observations. Anyone can join and it is a great website to confirm and share your observations. The maps on iNaturalist are continually updated as members post new observations. 

There are more photos at the bottom of the page, including those taken on 10-16-23.

THERE ARE SEVERAL LINKS AT THE BOTTOM OF THE PAGE FOR FURTHER READING AND TO HELP WITH A BETTER POSITIVE ID.

Symphyotrichum pilosum is a common sight on the farm and throughout the countryside. Some years more than others. I have difficulty identifying some species in the genus, but this one seems fairly easy with its smaller flowers, hairy stems, and hairy narrow leaves. Of course, there is more to it than that when it comes to making a proper ID.

There are more photos at the bottom of the page below the links for further reading.

Symphyotrichum pilosum is a U.S. native that can be found mainly from the central U.S. eastward. Although they prefer growing in full sun, I found a colony in a shady area behind the pond in the back pasture (at least I think it is S. pilosum). Unlike other species in the genus on the farm that like damp soil, this one has no problem at all with dry conditions. They aren’t really particular about the soil type either.

The Symphyotrichum pilosum is a clump-forming perennial that grows 1 to multiple stems from a branched, rhizomatous caudex. While this species normally grows no taller than 3 1/2’ tall, some information online suggests they can get as tall as 5’. The stems are green and pubescent (hairy), sometimes in longitudinal lines. As the plant ages, the lower part of the stems turns brown and the hair falls off. The stems branch out at the apex of leaf nodes where there can also be a cluster of small leaves. These side branches can be from 2” to 16” or so long depending on where they are along the main stems. The stems persist during the winter and often during the next summer.

Around here, most Symphyotrichum species are fairly late to emerge and bloom. While I was writing descriptions, I read once the flowering stems die down in the fall, the S. pilosum grows a rosette of basal leaves that stay green over the winter. So, I went out to where a plant is normally growing next to the gate by the barn to have a look on 3-23-23. Sure enough, there was a rosette of leaves… A week or so before, I had noticed several rosettes growing here and there, some with hairy leaves and some not. The ones without hairy leaves were undoubtedly other species.

The leaves are up to 3-4” long, elliptic to oblanceolate in shape, the margins being kind of toothed and hairy. These leaves taper to a rounded or bluntly pointed tip. The margins have blunt, shallow teeth and spreading hairs.

The upper surface of the basal leaves is medium green and covered with short hairs, while the undersurface is lighter green and somewhat hairy along the major veins.

I noticed several other rosettes in other areas with longer and narrower leaves.

In the spring, stems arise from the rosettes. The leaves grow in an alternate pattern along the stems that grow up to 3-4 1/2” long and 3/4-1” wide. The leaves grow smaller as they ascend the stem. The leaves at the lower to middle part of the stems are lanceolate-elliptic, oblanceolate-elliptic, or lanceolate in shape, have a few shallow teeth along the margins, and taper to a bluntly pointed tip. The leaves taper toward the base, the lower stem leaves broaden toward the base but are generally sessile (no petioles). The upper leaves are much smaller and usually have no teeth along the margins. The upper surface of the leaves is medium green and are usually rough from small hairs. The undersurface may be a lighter color and have hairs along the veins. The lower stem leaves usually turn brown and fall off before flowering occurs.

I briefly mentioned the “clusters of leaves” that grow at the apex of leaf nodes where the stem branches out. One website in particular says the leaves in these clusters become alternate leaves that grow along the growing branches…

Stems terminate in loose inflorescences of ramose branches or a single raceme. Hmmm… OK, so the flowering stems branch out and end with a few flower heads at the end. The stems have a multitude of leafy bracts (small leaves up to 1 1/4” long x 1/4” wide). Of course, they are also hairy. When the stems lean, close to horizontal, the flower heads move to the “sunny side.” 

The flower heads are approximately 1/2-3/4” in diameter and are surrounded by an urn or cup-shaped involucre.

The involucral bracts (phyllaries) are in 4-6 unequal and overlapping series. These bracts, especially the outer series are somewhat inrolled (or recurved) and are approximately 3/4” long.

The flower heads consist of 15-35 white ray florets (petals) in 1-2 series and 20-40 yellow tubular disc florets. There have been reports of the ray petals being light pink or light blue-violet, but this is rare. The disc florets have 4-5 recurved lobes and become reddish purple or reddish brown. A short peduncle (flower stem) joins the flower heads to the stem. 

The flowering period is from August to November. The plants are somewhat frost tolerant, but eventually, they get a good ZAP… 

Fertilized flowers are replaced seeds that are called achenes. These achenes have small tufts of white hair (pappus) that are carried away by the wind.

The flowers attract many species of bees, flies, wasps, small butterflies, skippers, and moths which feed on the nectar and pollen. Other species, including caterpillars, feed on the leaves, stems, flowers, and roots.

I will continue to take more photos as time goes on. It is always fun to try and take better and more detailed close-ups.

I have enjoyed photographing and learning about the many wildflowers growing on the farm I live on and in other areas. The farm is located in Windsor, Missouri in Pettis County (Henry County is across the street and Benton and Johnson aren’t far away). I have grown over 500 different plants and identified over 250 species of wildflowers (most have pages listed on the right side of the page). I am not an expert, botanist, or horticulturalist. I just like growing, photographing, and writing about my experience. I rely on several websites for ID and a few horticulturalists I contact if I cannot figure them out. Wildflowers can be somewhat variable from location to location, so sometimes it gets a bit confusing. If you see I have made an error, please let me know so I can correct what I have written.

I hope you found this page useful and be sure to check the links below for more information. They were written by experts and provide much more information. Some sites may not be up-to-date but they are always a work in progress. If you can, I would appreciate it if you would click on the “Like” below and leave a comment. It helps us bloggers stay motivated. You can also send an email to me at thebelmontrooster@yahoo.com. I would enjoy hearing from you especially if you notice something is a bit whacky.

FOR FURTHER READING:
PLANTS OF THE WORLD ONLINE (GENUS/SPECIES)
INTERNATIONAL PLANT NAMES INDEX (GENUS/SPECIES)
TROPICOS (GENUS/SPECIES)
FLORA OF MISSOURI (GENUS/SPECIES)
FLORA OF NORTH AMERICA (GENUS/SPECIES)
WORLD FLORA ONLINE (GENUS/SPECIES)
WIKIPEDIA (GENUS/SPECIES)
USDA PLANTS DATABASE
DAVE’S GARDEN
DAVE’S GARDEN ARTICLE
MISSOURI PLANTS
MISSOURI BOTANICAL GARDEN
MSU-MIDWEST WEEDS AND WILDFLOWERS
MISSOURI DEPARTMENT OF CONSERVATION
iNATURALIST
WILDFLOWER SEARCH
ARKANSAS NATIVE PLANT SOCIETY
ILLINOIS WILDFLOWERS
MINNESOTA WILDFLOWERS
KANSAS WILDFLOWERS AND GRASSES
NORTH CAROLINA STATE UNIVERSITY
GO BOTANY
LADY BIRD JOHNSON WILDFLOWER CENTER
UNIVERSITY OF WISCONSIN
MARYLAND BIODIVERSITY PROJECT
GARDENIA
U.S. WILDFLOWERS
UNIVERSITY OF WASHINGTON-BURKE HERBARIUM
ONTARIO WILDFLOWERS

NOTE: The data (figures, maps, accepted names, etc.) may not match on these websites. It depends on when and how they make updates and when their sources make updates. Some websites have hundreds and even many thousands of species to keep up with. Accepted scientific names change periodically and can be hard to keep with. Some of the links may use a name that is a synonym on other sites. In my opinion, Plants of the World Online by Kew is one of the most reliable and up-to-date plant databases and they make updates regularly. I make updates “at least” once a year and when I write new pages or add new photos but I do get behind. We are all a work in progress. 🙂

MORE PHOTOS…

 

 

 

 

 

 

 

In 2022, I had been watching a few colonies of Symphyotrichum lateriflorum (Calico Aster) and Symphyotrichum ontarionis (Ontario Aster) in a shady area behind the pond in the back pasture. I noticed a few plants that had hairy leaves. They turned out to be Symphyotrichum pilosum out of their normal habitat. They were smaller than usual for S. pilosum because they were growing in the shade…