Douglas' vs. Hall's Aster

[Don Boucher]

Hello,

Douglas' Aster (Symphyotrichum subspicatum) and Hall's Aster (Symphyotrichum hallii) are closely related and sometimes hard to distinguish due to their variability. They were formerly in the Aster genus. Both are native, occur in the Willamette Valley in full sun and bloom in late summer and into early fall.

At least in our area, the color difference is a primary indicator but not altogether reliable. Douglas' is violet-blue while Hall's is nearly white but there's some overlap, where both species may be pale-violet. There are two other common differences that are not absolute, but can help given all other factors. The ray flowers on Douglas' commonly overlap while Hall's are commonly separated. The lower leaves on Douglas' often have shallow teeth but not so with Hall's. The lower leaves on these Hall's plants happen to have withered.

Getting into finer details with the phyllaries (the scaly bracts underneath ray flowers), Douglas' phyllaries have longer, more narrow points.

These photos are from our native garden and they are larger plants, occurring in larger clusters than would be typical in the wild. In the wild, I find that Douglas' are often bigger plants than Hall's, especially when growing near wetlands. Hall's seem to tolerate drier conditions, eking along as puny plants but still managing to bloom.

The Willamette Valley Daisy (not pictured here - a.k.a. Willamette Fleabane - Erigeron decumbens) is similar at a glance but blooms only in spring and has very long leaves. It's also somewhat rare.

Don Boucher

[Joel Geier]

Thanks Don, this is very helpful.

We have Douglas' Aster on the lower part of our 1-1/4 acre property, but Hall's Aster on the hillside out back.

Joel

---

From: "Don Boucher" <donab...@gmail.com>
To: "Mid-Valley Nature" <mid-vall...@googlegroups.com>
Sent: Sunday, September 12, 2021 5:21:42 PM
Subject: [MidValleyNature:6139] Douglas' vs. Hall's Aster

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