Much like the goldenrods, this is "Asters for Dummies" and I'm only going to give a brief account of the flowers at first glance in the field. There are plenty of good websites detailing the finer points of aster identification; even so, what you can learn from looking at pictures on the Internet is rather limited. Experience is the best teacher – get out in the meadows, forests and wetlands with a good book and a camera.
Flat-topped White Aster (Doellingeria umbellata)
Height: Tall, approximately 100 cm
Habitat: Open areas along the Eastern Ontario Trail
Photographed: early to late August, still flowering in early September
The flat-topped panicles and sparse ray florets of this aster are distinctive.
Large-leaved Aster (Eurybia macrophylla)
Height: Tall, 100 to 120 cm
Habitat: Woodlands along the Eastern Ontario Trail
Photographed: early to mid August, still flowering in early September
Note the large, heart-shaped, stalked lower leaves, and stalkless upper leaves slightly clasping the stem.
The stems supporting the flower heads and phyllaries are downy; furthermore, the phyllaries don't spread and are blunt and rounded rather than terminating in a sharp point.
Heart-leaved Aster (Symphyotrichum cordifolium)
Height: Tall, 100 to 120 cm
Habitat: Open woodlands, Sheffield Conservation Area
Photographed: late August
The heart-shaped basal leaves are deeply notched where they meet the stem (compare to Large-leaved Aster above), the upper stem leaves are stalked and winged.
Photos of the phyllaries – note how they terminate in a point and lack the hairs typical of the Large-leaved Aster.
The upper stem leaves with their winged stalks.
New England Aster (Symphyotrichum novae-angliae)
Height: Tall, 100 to 120 cm
Habitat: Moist open fields along the Eastern Ontario Trail
Photographed: mid to late August, still flowering in early September
This aster stands out from the crowd, with its dense clusters of large flower heads composed of numerous, purplish-blue ray florets surrounding yellow disk florets.
A view of the phyllaries.
Purple-stemmed Aster (Symphyotrichum puniceum)
Height: Can be very tall, from 100 cm up to 150 cm
Habitat: Moist areas bordering marshes along the Eastern Ontario Trail
Photographed: early September
This aster can be a tough call. The hairy, purplish stems aren't always hairy or purple, and the ray florets can vary from pale blue to nearly purple.
Panicled Aster (Symphyotrichum lanceolatum)
Height: Tall, roughly 100 cm
Habitat: Moist, relatively open areas along the Eastern Ontario Trail
Photographed: late August, still flowering in early September
Open panicled flower clusters, flower heads with more ray florets and generally smaller lance-shaped leaves distinguish this species from the Flat-topped White Aster. This aster can be variable in form, making it hard to identify.
Heath Aster (Symphyotrichum ericoides)
Height: A short plant, most were no higher than 50 cm
Habitat: High, dry sandy hillsides bordering the Eastern Ontario Trail
Photographed: early September
Note the dense clusters of small white flower heads, with small leaves (dead or absent on the lower stem during flowering). The upper leaves and phyllaries are tipped with spines.
Calico Aster (Symphyotrichum lateriflorum)
Height: A small aster, 100 cm or less
Habitat: Open forested areas near the Point
Photographed: early September
Luxuriant clusters of small two-tone flowers on the upper sides of the gracefully arching stems are characteristic of this species.
Rush Aster (Symphyotrichum boreale)
Height: Small, most specimens were only about 30 cm high
Habitat: East Hungerford Road, near the Stoco Fen
Photographed: early September
A delicate, gracile wildflower with long narrow leaves bearing few flowers. This aster is not uncommon but isn't often encountered as it likes to get its feet wet, inhabiting in nutrient poor bogs and fens.
Arrow-leaved Aster (Symphyotrichum urophyllum)
Height: Fairly tall, close to 100 cm
Habitat: Open areas along the Eastern Ontario Trail
Photographed: early September
The close, upward sweeping stems catch the eye and are according to the book for this species. However, this aster proved challenging in certain other respects, and I'm still not entirely happy with some of the particulars of my study.
This is a bit bothersome ... the involucres and phyllaries aren't quite as illustrated on reliable Internet resources. But then, this specimen as a whole has a relatively pale aspect – including the disk florets – which should theoretically turn purple with age, not the pale brown I'm seeing. I guess asters don't read our field guides ...
The hairless stem and shallowly toothed leaves with winged stalks are correct for this species. These leaves were located on the lower part of the stem (but there was no evidence of true basal leaves).
Top and underside views of a narrower leaf, situated higher on the stem.
For the most part the characteristics of this plant conform to those given for the Arrow-leaved Aster, but I'm going to re-visit it in the near future to see if there are any changes as it ages. Here are some links to other studies of the Arrow-leaved Aster ...
Ontario Wildflowers
Nature through the Lens
Robert W. Freckmann Herbarium (University of Wisconsin)
