Plant Species of San Jacinto Mountain: Distinguishing Erigeron breweri var. covillei and Erigeron foliosus var. foliosus

The Erigeron foliosus - E. breweri complex is one of the most difficult in the genus Erigeron; see the Introduction in my page on E. breweri var. covillei. Var. covillei is perhaps especially problematic, since botanists have treated var. covillei sometimes as part of E. foliosus and sometimes as part of E. breweri.

The Jepson eflora key to separate E. foliosus from E. breweri is:

49. Stem hairs dense, stiffly spreading, generally slightly reflexed ==> E. breweri
49' Stem hairs 0 or sparse, appressed ==> E. foliosus

This sounds like a nice clear discriminant and pretty easy, right?

So perhaps it was understandable that I was puzzled when I first saw plants of Erigeron breweri var. covillei on the PCT north of SR74, since they had a considerable variation in stem hairs, with some plants having the spreading stem hairs of E. foliosus and some plants having the appressed stem hairs of E. breweri. It was only years later that I finally convinced myself all those plants were E. breweri.

This page shows the differences between the two species in the Desert Divide area. Even when the stem hairs appear the same between the two species, there are a number of other differences that can distinguish them.

The overall gestalt of the plants is quite different. E. breweri is a short plant with a few ascending grayish-green stems, whereas E. foliosus is a tall plant with many mostly-erect usually-green stems; see Fig. 1. It is easy to pinpoint the base of the stems of E. breweri, since the plants are usually well separated with few stems, whereas E. foliosus often appears as a large mass of stems, with the bases not apparent.

E. breweri var. covillei

E. foliosus var. foliosus

Fig. 1. The overall gestalt of the two species. Left: E. breweri var. covillei, photographed on the PCT North of SR74 on 10 June 2009. Right: E. foliosus var. foliosus, photographed on the PCT from Fobes to Palm View Peak on 7 July 2009. Click on the pictures for larger versions.


The leaves of the two species are usually quite different. The leaves of E. breweri are broader and often oblanceolate, and are much more noticeable than the linear and very narrow leaves of E. foliosus; see Fig. 2. However, the first leaves of E. foliosus can be similar in shape to those of E. breweri.

E. breweri var. covillei

E. foliosus var. foliosus

Fig. 2. The differences in the appearance of the stem and leaves of the two species. Note the hairier stems of E. breweri, and the wider leaves. Left: E. breweri var. covillei, photographed on the PCT North of SR74 on 31 May 2018. Right: E. foliosus var. foliosus, photographed on the PCT from Fobes to Palm View Peak on 7 July 2009. Click on the pictures for larger versions.


The stem and leaf hairs are usually quite different, but not always; see Fig. 2. This was what confused me when I first saw plants of E. breweri on the PCT north of SR74, since some plants had the typical stem and leaf hairs of E. breweri, but other plants had hairs that were not very different from those of E. foliosus. See my page on E. breweri var. covillei for the variation in the hairs. In addition, the lowermost stems of E. foliosus can have spreading hairs identical to those of E. breweri; see example of a plant from the Ernie Maxwell Trail showing both types of hairs on a lower stem. But as far as I know, E. foliosus only has appressed hairs in its upper stem.

The floras note that the hairs of E. breweri var. covillei have widened bases, making them almost lanceolate in appearance; see Fig. 3. The floras do not comment on the hairs of E. foliosus var. foliosus, but our plants of E. foliosus also can have hairs with widened bases. See a photograph of the leaf hairs for E. foliosus from the same plant on the Ernie Maxwell trail with the spreading hairs on its lower stem and sparse appressed hairs on its upper stem.

E. breweri var. covillei

E. foliosus var. foliosus

Fig. 3. Comparison of the stem hairs. Left: E. breweri var. covillei photographed on the PCT North of SR74 on 31 May 2018. Note the almost-lanceolate shape of the hairs, due to the widened bases. Right: E. foliosus var. foliosus, photographed at Idyllwild Park on 21 June 2010. The stem hairs are also expanded a bit at their bases. This photograph was of the stem immediately below the flower, so is not exactly comparable to the mid-stem photograph of E. breweri var. covillei if the hairs vary along the stem.


There may be a difference in several features of the flowers, but I need to see more flowers to determine whether this is the case. In the one example shown here, the ray flowers of E. breweri are shorter, and relatively wider than the ray flowers of E. foliosus, with a narrowly oblanceolate shape compared to a linear shape, similar to the leaf differences. The Jepson Manual gives the length of the ray for E. breweri covillei as 4 to 7 mm, compared to 6 to 11 mm for E. foliosus var. foliosus, so the difference in ray length is probably significant. See Fig. 4.

In this example, the ray petals are ascending for E. breweri, compared to the spreading petals of E. foliosus. However, the position of the ray petals might vary with the time of day for both species, making this apparent difference an artifact of when I photographed the flowers.

Interestingly, the hairs on the phyllaries appear to be much the same for the two species.

E. breweri var. covillei

E. foliosus var. foliosus

Fig. 4. The flower heads of the two species. Left: E. breweri var. covillei, photographed on the PCT North of SR74 on 10 June 2009. Right: E. foliosus var. foliosus, photographed on the PCT from Fobes to Palm View Peak on 7 July 2009. Click on the pictures for larger versions.


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Copyright © 2018 by Tom Chester.
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Comments and feedback: Tom Chester
Updated 6 June 2018.