If you are the type of plant nerd who craves rarity, then the Poaceae is likely not for you.
The adaptability of grasses as a whole means that individual species tend to be geographically widespread and able to exist in diverse environments. There are rare and endemic grasses, but they tend to be in the minority, and most don't really have any unusual features that sets them apart from the rest of the family.
We were hiking the skyline loop near Mt. Rainier in Washington State this September when I stumbled on a grass that really caught my eye. This long trail skirts the side of the dormant volcano, starting at 1600 meters above sea level and gaining altitude to a maximum elevation of more than 2000 meters. The sub-alpine environment is rocky and tree-less, with low lying plants, including various unremarkable graminoids.
But one particular specimen next to the path suddenly made me stop in my tracks.
The grass was half hidden behind one of the many rocks that littered the trail, and its slender stalks ended in gracefully drooping spikelets. It was a rather handsome specimen, but what made me really pay attention was the fact the entire plant was a dark purplish color! In fact, it looked even darker hued than my ornamental Andropogon gerardii 'Blackhawk", and it really stood out in the bright morning sun.
Unfortunately, I did not bring my macro lens on the hike, but I made do with the 50 mm lens and took a few pictures of the plant habit and spikelets..
When I returned home I spent some time trying to identify the specimen from the images I took, and finally decided that it was Vahlodea atropurpurea, which is also called Mountain Hair Grass.
This subalpine/alpine species is fairly rare, though circumboreal, and considered endangered in several places, including California and the New England states. It is not considered globally endangered, but I was still happy to have stumbled on the species during the hike, as its discovery reminded me that it is still possible to find quite unusual grasses even in touristy areas like Mt. Rainier.