Flora and fauna of the Athens County area, and occasionally habitats outside Ohio. Subject matter will consist of both interpretive material and taxonomic issues in plant and animal identification.

Sunday, November 20, 2011

Some Ohio Asters

Ah the Asters, could it get more difficult? I want to thank Scott Namestnik of "Get Your Botany On" for reviewing some of these photographs. Both of us will tell you that identifying asters from photos alone can be very unreliable. Even if you're just a photographer, collecting and pressing voucher specimens for detailed observation is often a must to be sure. I have sent these pictures to others, but am still waiting for responses.  Should opinions change on anything posted here, I'll be sure to update them. Comments and corrections are welcome.

Asters are part of the Composite family Asteraceae. Their flower heads are yellow-green to red, and the rays range from white to lavender or purple. Once thought to be related to the old world Aster genus, we now know they are different, and have been split into at least three other genera.

Because flower color can vary within the same species, it is critical to have leaf descriptions to narrow down the proper identification. Leaves can vary from serrate to entire, stalked or unstalked, and even clasping the stem. With most species the lower leaves on the plant are often different from the upper leaves.

Making it even a greater challenge are species like this which show both large and small leaves interspersed throughout the stem. Especially confusing are these white asters where people will say "the flowers are more crowded on the stem". Or descriptions like "this species has slightly larger flowers". I'm sorry, but that is a bit vague for me. I suppose if you work with these ALL the time, or are comparing several species growing nearby, that might be okay, but doesn't do much for beginning identification.

Here is an example. Yes, the flowers on the left are a bit larger than the ones on the right, but how often do they all grow side by side? Usually they are out by themselves. What is important on these two is the left one has large broad leaves, and the species on the right has small narrow leaves. Always keep leaves in mind with Asters.

Let's try and make sense of some of the species. Without a doubt, the showiest and easiest species to identify is the New England Aster, Symphyotrichum novae-angliae. They have more rays than other asters.

This is one of our largest flowering species. They grow in any abandoned field, usually in large clumps. You can identify this one just driving by them. They reach four feet in height.

Up close their leaves are entire, but covered in hairs, as is the stem. The leaves are crowded together and clasp around the stem. As I said, this is the one species you need not have to look at this close to be sure.

If while driving around, you see an aster growing in ditches that appears somewhat similar to New England, but seems a bit lighter in color, and has fewer flowers up top, you may be looking at Purple-stemmed Aster, Symphyotrichum puniceum.

Purple-stemmed Aster is a species that likes aquatic environments. Notice the cattails in the background.

The leaves clasp the stem like New England, but not nearly as much. The leaves are more spread out along the stem. The stem can be red to purple and covered with hairs. What's different about this species is the hairs are not soft but stiff.

Another tall species is Smooth Aster, Symphyotrichum laeve. While commonly 3 feet in growth, I have seen them 4-5 feet tall.

The key feature I find on this species is the long leaves that usually have no teeth. They are thick and leathery to the touch. Both the leaves and the stem are smooth and hairless, so the common name is appropriate.

Up close you can see this is another species with very obvious clasping leaves. Look for this plant on the edges of dry woods.

Another showy aster with pale lavender flowers is the Crooked-stemmed Aster, Symphyotrichum prenanthoides. So far I would group New England and Purple-stemmed as having very large flowers as asters go. Smooth and Crooked-stem have medium sized flowers. Oh my, forgive me if I now sound vague as well. After looking at all parts of Crooked-stem Aster, you won't need to worry about flower size anyway.

Continuing our theme of clasping leaved species, here is another. I must admit I didn't plan it that way, as I have these in no particular order. If all you do is look at the leaf base, it probably looks nearly identical to Smooth. Of course we won't limit ourselves to just that. Follow the leaf up the margin. You will see they are always serrate. The stems on this plant are hairy not smooth.

The leaves are broad and sharply toothed at the middle and top, then narrow down to form a wing before clasping the stem.

As with the previous species, the common name tells us what to look for the most. The stem tends to grow crooked or zig-zag at every node, especially further up the plant. Look for this in moist to wet woods and edges.

Departing from the purple species for a moment, here is the Flat-topped Aster, Doellingeria umbellata.  The flowers are all located at the top of the plant. They may be on an even plane (flat-topped) or slightly curved or domed like an umbrella (umbellata). The leaves are elongate, narrow and almost willow like. They are distinctly veined and the margins are toothless or weakly serrate. I have seen this plant in open marshes and wet woods.

Another white flowered species is Eurybia divaricata. Common names include White Wood Aster and Heart-leaved Aster. This is a woodland species. I have found it in both wet and dry woods. Either way, it prefers shade.

White Wood Aster tells us where to look for it, Heart-leaved Aster tells us what to look for. Like the previous species, the flower heads are flat-topped, but the leaves are heart shaped with very large coarse teeth on the margin. The flower heads are less numerous than many of the smaller white asters.

The leaves are distinctly stalked, especially lower on the plant. The upper most leaves may sometimes form short wings, as seen in the first photo of this species. The main stem is often twining or somewhat crooked.

Up till now these asters may be considered confusing, but not that tough. Now let's look at the difficult ones. The silhouette of this picture is similar to the previous, with some major differences. The flower cluster is more elongated or panicled, and the rays are blue-purple. This is the Blue Wood or Arrow-leaved Aster, Symphyotrichum cordifolium.

The variability in color makes looking at the flowers alone unreliable. There are similar looking broad leaved species like cordifolium. I have never been able to separate this from sagittifolius or lowrieanus. Turns out, (according to some) they are the same thing, now called urophyllum. Of course it depends whether you are a lumper or splitter. To my understanding S. drummondii is still a valid species. It is much hairier than cordifolium.

In the first of these photos, S. cordifolium usually has long narrow petioles throughout the plant. Whether you consider them different or just varieties, the others have petioles that are broader and form these wings to the stem. Look for these species in dry to mesic woodlands with openings in the canopy.

The jury is still out on this one, but I believe this is Wavy-leaved Aster, Symphyotrichum undulatum (or undulatus). This is another woodland species with light blue flowers.

The leaf shape is key here. The lower leaves are broad, toothed, and with long petioles. The difference with this one is the narrow petioles suddenly enlarge into a wing at the base, and the leaves then clasp the stem. The middle leaves have a shorter petiole that is still winged, and the leaf margin becomes less serrate.

The upper most leaves show no petiole and appear sessile. The margins become entire. These look a little like Smooth aster, but the leaves are rough to the touch, and the stem is hairy. Three different portions of the plant, with this much variation, shows why asters are not easy to identify.

Back to the white asters, this is Panicled Aster, Symphyotrichum lanceolatum. This was formerly known as Aster simplex.

What I look for in this species are the long, narrow or lance shaped leaves. They are weakly toothed to sometimes entire. They do not clasp the stem. Look for small leaves intermingled among the long ones. The stems are angled, and the raised portions are lined in fine hairs.

This is a common species. Considered weedy by many, it's panicled flowers can be quite showy. They are 1/2 to 3/4 of an inch across. Look for it in any wet soils.

Now come the most commonly seen asters in open fields. These are species of "bushy" asters. Most people lump them all into Calico asters, but this is not the case. There are several lookalikes.

Because they form such dense thickets in fields, they are often overlooked or taken for granted they're all the same thing. I have trouble separating them. The leaves on this are very small near the top. They are linear in shape and usually entire, but you have to check the stems. This is the Frost Aster, Symphyotrichum pilosum.

The stems on this plant are covered with silky white hairs. The leaf margins also contain these same hairs. It is said the name Frost Aster comes from the fact the plants look like frozen dew on a cold autumn morning. The hairs stand straight out. Other similar species have hairs that curl or are appressed upward to the twig. If that's the case, everything I come across from Northern to Southern Ohio has been this species. I'd say it's more than common, I'd call it quite abundant.

Now if this one is starting to look more like Symphyotrichum lateriflorum, the Calico Aster, you are correct. Notice the rays on this species number a lot fewer than other asters. The flowers are also much smaller than the other types. It is not really important to count the rays or measure them. As I said earlier, saying things like fewer and smaller when talking about only one species doesn't help much. I only choose those words to COMPARE against other similar species.

It is often noted that Calico can be identified by the red flower centers, but this is not reliable. Early on they are all white. Most if not all the smaller asters will have the flower head turn reddish with time. Size and number of rays are what to look for.

Of course we can't do asters without going back to the leaves. Calico leaves vary in length, but may be several inches long. The larger ones will be coarsely toothed, and the small upper leaves will be entire. The stems will be smooth to slightly hairy. The hairs are usually restricted to thin lines or rows. The green bracts (pic 1 & 4) stay appressed up against the flower head. On others like Frost or Heath Aster, they tend to curve outward. They occur in open fields, but may be more common on the edge of moist woodlands.

Here's another group I can't separate. This is the racemosum/ericoides group. Common names include the Heath Aster, Small White, Smooth White, and Old Field Aster. Superficially they look like any of the white bushy asters. What's different are the leaves. They are reduced in size, tend to look rolled, linear, or awl shaped. Heath plants have leaves like this, but conifers like Fir, Larch or Spruce come to mind when I see these plants. This group of asters tend to hybridize, so I can't be sure which is which.

Quiz time?  Well as I mentioned early on, if you can't see the leaves, don't even try. This staged photo just shows that when side by side, there really is a difference between them. I did find all of these along the same road though. How many can you see? There are six species here. New England, the most obvious in the middle. The far right has the small Calico. To the left of that is Frost. Up in the top left is the Crooked-stem. The light blue next to N.E. is Smooth aster, and at the far left is Arrow-leaved.

Addendum: I realize this is a long post, but that is on purpose. I have done that in the past with some moth posts as well as sunflower/coneflowers and others. Last year an entire class used my grasses post. I hope these will become references for later use. I will try Goldenrods and a large post on Oak trees in the near future. Be careful trying to absorb too much. A moment of silence please. Holly, one of my followers, had her head explode after reading this blog!!   (smile)


  1. Love your blog,and my head just exploded

  2. Great post very informative, I'm glad to have found such a great resource for such a tricky native topic of wild aster identification!

  3. Great post, Dennis! I made a strong effort to come across and photograph as many native species of Aster as possible this season and managed 23 species! Such fun and yet difficult plants.

  4. Thank u so very much 4 the very detailed comprehensive info!!!!!! Your info is very valuable 4 those of us outside of OH too! So a BIG thank u from a researcher in Delaware (no not Delaware, OH, the 1st state :O)

  5. Very helpful! I have some "old field aster" in my yard that I like... But it seeds so profusely I was worried it might be an invasive exotic species. It looks like it's probably what you described though. Thanks