Aristida purpurea is an uncommon grass in the Kamloops area. It is much more common in the south Okanagan but you do occasionally come across it in our area.

It grows on coarse-textured or rocky soils often on steep slopes with a warm aspect that experience very hot and very dry conditions during the summer months. It is particularly abundant along the lower slopes at the west end of Kamloops Lake that are heavily grazed. It is not a very nutritious grass and the mature awns are not appetizing for livestock so it tends to be avoided in favour of other grasses like bluebunch wheatgrass.

It often has a reddish colouration to the developing seed heads and leaves in the spring and early summer.

Most plants carry out what is called C3 photosynthesis (the first compound produced during photosynthesis has three carbon atoms). However, red three-awn and other species, that often grow in areas subject to high light levels, high temperatures, and drought conditions have developed a slightly different type of photosynthesis called C4 photosynthesis (the first compound produced during photosynthesis has four carbon atoms) which allows it to be more efficient at photosynthesis and water use but are less competitive than C3 plants in less-demanding habitats.

I like red three-awn because it is one of the most easily recognizable grasses in the Kamloops area. Like needle-and-thread grass, red three-awn produces seeds that have large awns. However, each seed of red three-awn as the name suggests has three awns that are bent at right-angles when mature.

It’s a difficult grass to photograph (as are a lot of grasses) but hopefully from the above photographs you can see the distinctive three awns attached to each seed that sort of look like the rotor blades of a helicopter.