Plant Species of the Borrego Desert: Boraginaceae: Cryptantha micrantha, red-root cryptantha

Fig. 1.
Left: Two plants of Cryptantha micrantha var. micrantha from Butler Canyon, 9 April 2009. The plant on the left germinated from the first winter rain, and grew big and strong. The plant on the right germinated from a late winter rain, and shows the more typical appearance of this species here.

Right: Closeup of the more typical form of this taxon seen in most years, from Smuggler Canyon Wash on 9 February 2012. There was just barely enough rain in 2012 to germinate this species here. There was essentially no annual germination farther north.

Click on the pictures to get larger versions.

Cryptantha micrantha is one of our most recognizable cryptanthas. After you have learned this species, you can usually confidently recognize it by sight from a standing position, even though the plants are typically just a few inches tall, since it has a distinctive gestalt. In its habitat of flat sandy areas or sandy drainages, it is the expected species, although a few other of our cryptantha species also grow in washes. Fortunately, if you are in doubt about the determination of a plant, there is a killer feature that confidently gives its identification: the presence of a leafy bract under every single flower. None of our other cryptanthas have a bract under every single flower. Most of our other cryptanthas have no bracts under any of their flowers. A few species have a leafy bract under a few flowers, but never under every flower.

Pictures with the leafy bracts labeled: from a top view and from a side view.

Another trait that helps identify this species is the red root of its name. However, since this feature is only visible by digging around the base of the plant, it is not recommended, because it may harm the plant and because this trait is not needed for the identification. See pictures of three plants and their roots.

Our plants are typically taller than wide, and very slender. This trait confuses beginning botanists who remember that they key under plants wider than tall in one branch of the First Edition Jepson Manual key, but who do not notice that they key under plants taller than wide in another branch. It also confuses those who note that the Second Edition Jepson Manual keys this species under generally wider than tall and describes it as ± cushion-like.

Basically, the height to width ratio of the plants depends solely on moisture. Most of the time, the plants only get enough rainfall to produce a single stem, and are taller than wide. Only in the best conditions in the best years do the plants get enough water to branch out in their full glory, and become wider than tall.

We have two varieties of this species in the Borrego Desert that are so different I'm very surprised they aren't classified as separate species (see Fig. 2). They have dramatically different flower sizes: var. micrantha has almost unnoticeably-small flowers only 2 mm across, and var. lepida has very showy flowers typically 5 mm across that have ~6 times the area. (i.e., if you are looking at the flower straight-on, as most people and photographers do, you could place six var. micrantha flowers inside a single flower of var. lepida. I've never seen them intergrade.

Fig. 2. The two varieties of Cryptantha micrantha, growing together in The Potrero, 2 April 2012, one of the few locations where both varieties grow together. The plant on the left is var. micrantha, showing buds and one completely-open flower. The plant on the right is var. lepida, with a number of completely-open flowers. The plants in this picture were selected only because they were growing side-by-side; there is nothing unusual about the size of the flowers for each variety.

Click on the picture to get a larger version.

Plants of the desert floor in San Diego County, up to about 2000 feet elevation, are all the small-flowered var. micrantha. Plants in the mountains in San Diego County, down to about 3500 feet elevation, are all the large-flowered var. lepida, with the common name (used here) of mountain red-root cryptantha. Between 2000 and 3500 feet elevation, both varieties can grow together.

The geographic variation of vouchered plants is shown in the following maps from the Consortium of California Herbaria: var. lepida and var. micrantha. Those maps are on the same scale, and can be opened in two separate browser windows, superimposed, and then you can flip between them with alt-tab. The voucher of var. micrantha that plots in Cuyamaca Rancho State Park is possibly a misdetermination or some other error.

An old name for Cryptantha micrantha is Eremocarya micrantha, which will probably be restored as the new name for this species in a future online update of the 2012 Jepson Manual. This species is so unique that it is the only species in the Eremocarya genus. See Hasenstab-Lehman and Simpson 2012, the paper giving the phylogenetic reasons behind restoring that old genera.

Botanists sometimes confuse our plants with Cryptantha circumscissa, which is a very harsh-bristly species that looks completely different in gestalt, and which has two killer distinctions from C. micrantha:

Cryptantha circumscissa is mostly a Mojave Desert species. In Anza-Borrego Desert State Park, it is found only at elevations above 3500 feet near Whale Peak.

Additional pictures of these two varieties of C. micrantha are shown below. Click on them to get larger versions.

Fig. 3. Var. micrantha plants at Lower Willows, 30 April 2010.
Fig. 4. Var. micrantha plants at Mine Wash, 3 February 2011, with the 0.8 mm diameter tip of a Pilot Razor Point pen for scale.
Fig. 5 (four rows of pictures). Var. lepida and var. micrantha plants at The Potrero, 2 April 2012.

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Updated 29 December 2012