Thanks once again to Michael Charters (of Calflora.net) for contributing some images to Botany Photo of the Day (submitted via the BPotD Submissions forum | original image in this thread). Michael has also been busily updating his “What’s Blooming at the Los Angeles County Arboretum?”, if you haven’t visited that site for a few months.
Like yesterday’s Hibiscus clayi, Swallenia alexandrae is an endangered species. Its common name reflects its locality: Eureka Valley dunegrass. This Californian endemic only grows on the shifting sand dunes of this small area located in the northern part of Death Valley National Park.
The scientific description and naming of this species was first published in 1963. Fifteen years later, it was listed as an endangered species. Part of the reason, it is fair to say, is due to its restricted locality – it would have to be considered vulnerable to stochastic (random) events even if human disturbance wasn’t an issue simply because of the narrow ecological conditions and area in which it is found. Unfortunately, as is too often the case, human impact on the species has resulted in a decline. Prior to attentive management of the area (and prior to this area being added to the park), off-road vehicle recreation was responsible for destroying plants. The wheels of the vehicles would tear apart the rhizomes of the plants (a rhizome is illustrated in the first photograph), subjecting them to water loss and eventual death.
The increased monitoring of the site after off-road vehicle use was banned helped stabilize the population (though as the above link notes, the ban was not always observed). Two more recent threats have emerged, though: competition with Russian thistle (Salsola sp.) and sandboarding. The spread of the non-native Salsola had been helped along by the disturbances of the off-road vehicles – the “gift that keeps on giving”, so to speak.
A scientific description of the plant is available on this page – sorry, no obvious link to related pages can be found with this resource, but it’s on the Conservation Management Institute‘s web server. More photographs of Swallenia alexandrae are available via CalPhotos.