Distinguishing young rosettes of Malacothrix glabrata, desert dandelion, and Chaenactis fremontii, Fremont pincushion

Malacothrix glabrataChaenactis fremontii
Fig. 1. Left: Malacothrix glabrata, desert dandelion. Right: Chaenactis fremontii, Fremont pincushion. There is no problem distinguishing these species when they are in bloom! But it is more difficult to distinguish them when they are young plants.
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Introduction

These two species are trivial to separate when in flower, as shown in Fig. 1, and fairly easy to separate when they are large enough to think about sending up flower stalks, as shown in Fig. 2.

Fig. 2. Malacothrix glabrata, desert dandelion, rosettes on the left, and Chaenactis fremontii, Fremont pincushion, rosettes on the right. Top: View from above. Bottom: View from the side.
At this stage, M. glabrata is a more sprawling plant, with more delicate leaves, whereas C. fremontii is a somewhat-more erect plant, with somewhat-thicker leaves.
Click on the pictures for larger versions.

For some time, I thought that it was difficult or impossible to reliably discriminate younger plants of these two species. However, after putting a number of photos of young plants online, and getting feedback from James Dillane, Jane Strong, and Keir Morse, I think that most of the time it should be possible to identify the two species when they are young plants without buds or bloom.

My main difficulty was that I had been trying to make two species out of young plants of Chaenactis fremontii, which is always problematic! Given the similarity in overall appearance of vegetative plants such as the ones shown in Fig. 2, I had thought young plants of Malacothrix glabrata would resemble young plants of Chaenactis fremontii, but that turns out not to be the case.

Very young plants of Malacothrix glabrata look like a grass like Schismus, with very thin insubstantial leaves! In contrast, young plants of Chaenactis fremontii have more substantial leaves, and would never be confused with a grass (see Fig. 3). Even though the abundance of these two species is similar, I have very few pix of young plants of Malacothrix glabrata, probably because I mistook them for Schismus in the past, and ignored them.

It is not easy from a standing position to distinguish very young plants of Malacothrix glabrata from Schismus barbatus. With a hand lens, one can check for the ~5 parallel veins of Schismus to distinguish it from the non-parallel venation of Malacothrix, or check for the multiple leaves per stem (bunched at the base of the stem) for Schismus.

More mature plants of Malacothrix glabrata no longer look like a grass, and are easily distinguished from Schismus in overall gestalt, including having lobes on the leaves.

As the young plants of Malacothrix glabrata and Chaenactis fremontii begin to produce their flowering stalks, separation of the two species becomes easier, since C. fremontii usually initally has a single erect stalk, and M. glabrata has a number of ascending stalks. Once buds appear, they are easy to distinguish, since the buds of M. glabrata are nodding and those of C. fremontii are not, and the phyllaries are quite different even in bud. Of course, once the flowers appear, no one could possibly confuse them.

Fig. 3 shows a number of young plants of both species, arranged from the most mature, and most easily-recognized, plants at the top, to the youngest plants at the bottom.

Note that the leaves of both Malacothrix glabrata and Chaenactis fremontii can be quite variable, in how erect they are; their cross-sectional shape (round vs. flat); their lobing (none to having a number of lobes); and their coloration (green vs. red). Both species can have a groove on the upper part of their leaf when there are lobes (James Dillane pointed out that the groove appears to be caused by the lobes being decurrent on the main leaf axis).

Malacothrix glabrataChaenactis fremontii
Fig. 3. Plants arranged with the youngest plants in the bottom row, and the oldest plants in the top row. Left: Malacothrix glabrata. Right: Chaenactis fremontii.
Important caveat. I have used the gestalt of the young plants to determine them, and I have not followed the young plants to flowering. Hence although I think it is likely that I have the species assignments correct for the youngest plants, I don't guarantee it.
Click on the pictures for larger versions.


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Updated 31 January 2016