Fieldwork Short: Would a Sagebrush by Any Other Name Glow As Blue?

Meet Artemisia tridentata ssp.* vaseyana (mountain big sagebrush), one of the great loves of my life and the star of the plant communities I study. This amazing aromatic evergreen shrub is a crucial food source for ungulates like pronghorn and elk throughout the winter, it creates islands of fertility and shade for other plants, and it is home to a variety of birds which rely on its structure for nesting. There are actually several (6) subspecies of this sagebrush of which three are the most prominent- ssp. wyomingensis, ssp. tridentata, and ssp. vaseyana. The latter species grows in my study region while the other two can be found in other areas of WY and the west in general.

Artemisia tridentata ssp. vaseyana is identifiable by its large shrubby structure with tall flower stalks that result in an “even top” and leaves with three shallow lobes. Other species of sagebrush in the west also have three lobes but the depth of their separation and general size and structure of the plants are very different (see the photo of Artemisia tripartita).

However, the identification of the different subspecies is incredibly tricky even for trained botanists because the differences between subspecies are slight and variation in appearance great. Yet ssp. vaseyana has a fun secret which helps with its identification- it glows under a UV light when wet!! The reaction is best captured with crushed leaves under water, but in my video I show you just a glimpse of the silvery-blue hue they produce when fluoresced. It is subtle but very cool and the other ssp. do not glow in this way, which makes UV fluorescence a useful technique for ID. It is thought that compounds called coumarins could be responsible for this amazing reaction as they are known to fluoresce.

Some may wonder why it is important to make such a slight distinction, but it has been shown that each ssp. can have a very different chemical profile which is important to species that eat sagebrush because it affects palatability and each ssp. is specially adapted genetically and physiologically to the landscape. Therefore, ecologists working in restoration must consider which ssp. are appropriate for use in plantings and conservationists are interested in how hybridization might impact populations of these adapted ssp. in the future.

* ssp. is the standard scientific abbreviation for subspecies

Cheers! -Häslein (aka FBK, aka Sienna)