Guide to small white asters (Symphyotrichum sp.)

 Here is my working guide to white asters (Symphyotrichum sp.)(without heart-shaped leaves) in central and Northern New Jersey. Note that all of these can have purple flowers as well, though uncommonly.

The phyllary bracts are extremely important (the green bits below the "flower") 

Heath aster  is the only one with pointy, all-green, divergent bracts

Calico aster is the only one with very wide-spread, even curved-back disc flowers

Frost aster is the only one with sort of urn-shaped phyllaries and the only one with green, needle-shaped, spreading bracts that curve away from the stem

Small white and panicled asters both have green striped bracts (calico has green-tipped, spotted looking bracts). 

The number of rays and the size of the rays are important. Heath and calico have smaller flowers with few rays. Small white has small flowers with many rays.

The overall shape of the flower cluster is important. Is it widely branching? (if not, then not heath or small white). Is it one-sided (if not, then not small white).

Leaves are generally unimportant, but only calico and panicled can have leaves that are not linear.

	S. ericoides	S. lateriflora	S. pilosum	S. racemosum	S. lanceolatum
	heath	calico	frost	Sm white	panicled
rays	8-20	9-14	16-35	15-30	20-40
disk		recurved
one-sided?	some		some	usually
branching	Divergent recurved	Widely branch Or simple	Oft. diffuse	Open  Divergent Oft. racemous	elongate
leaves		Sometimes not  linear
Leaf bases				Sometimes clasp	Sometimes petiole-like
Leaf max. (cm)	6 x 0.7	15 x 3	10 x 1	11 x 1	15 x 3
involucre			Constricted (urn-shaped)
bracts	loose		Loose
tips of bracts	With sharp point	Fairly broad green tip	Inrolled margins	Elongate green tip	Elongate green tip
Rays clearly longer than green base (involucre)	no	no	probably	yes, though flowers are small.	yes
location	dry	dry		Moist	moist

S. dumosum, though not common according to iNaturalist in NJ, should also be present. It would have long, bracty stems on flowerheads, bracts green and appressed, 12-20 not terribly long rays, smallish linear leaves.