Needle and ricegrasses

During the 2020-2021 field seasons I spent a lot of time with various ricegrasses and needlegrasses. It started with an interest in Henderson's ricegrass in scablands in the Ochoco Mountains, which led to looking for Wallowa ricegrass. In July 2020, botanists attending my workshop asked for help with needlegrass species so we gave extra empasis to them. We saw Nelson's needlegrass and Lemmon's needlegrass at our field sites and one of the botanists brought samples of the special rare one in Oregon: Richardson's needlegrass. That led to one of the botanists going back to her forest to look for pine needlegrass. I've been using common names because I'm still adjusting to a name change published while our field guide was at the printer.  None of those taxa are called Achnatherum anymore. They've been renamed, and are now Eriocoma. Here is a link to the article. Of course, we still have Hesperostipa, Piptatheropsis, Pappostipa, Oryzopsis, and Nassella. Eriocoma may feel new to us, but it dates back to 1818, when Thomas Nuttall bestowed in on silkgrass (Indian ricegrass). 

 Two of our needlegrasses, Indian ricegrass and needle-and-thread, love sandy soils. As one of my soil scientist friends commented, these two species grow on the soils that don't rise into a cloud of dust behind your vehicle on soft unpaved roads.

Needle-and-thread

Hesperostipa comata_habit.jpg

The spikelets with long glumes and long-awned florets are so distinctive that this species is immediately recognizable when flowering. During the remainder of the year, I look for large clumps of relatively coarse stiff leaves, tall culms, and long glumes to identify this species on sandy soils.

Hesperostipa comata_spikelets.jpg

The common name "needle-and-thread" describes the sharp hard lemma and long slender awn of Hesperostipa comata. This species was formerly in the genus Stipa, but when that genus was narrowed to Old World species, ours became hespero (western) stipa.

Hesperostipa comata_Badlands.jpg

Indian ricegrass (Eriocoma hymenoides)

Eriocoma hymenoides spikelet_edited.jpg

Indian ricegrass florets are awned, but the awns are the polar opposite of those of needle-and-thread. They are short, soft, and fall off at maturity. Actually, you could be around Indian ricegrass for years before realizing that it has awns. In the image (left) the awn has fallen. The soft, silky hairs covering the lemma body are about as long as the glumes. The plump seeds have been used as a food source by humans, thus the common names Indian millet or ricegrass.

Indian rice grass panicles branch profusely and bear a single spikelet with a single floret at the tip of each branchlet. None of the other Eriocoma species have this branching pattern.

Achnatherum hymenoides_habit.jpg

Henderson's ricegrass (Eriocoma hendersonii)

Achnatherum hendersonii habit_edited.jpg

This ricegrass grows on shallow rocky soils. Its panicle is erect with ascending branches. The florets are shiny dark brown with a deciduous awn. 

Henderson's ricegrass is a regional endemic, growing only in eastern Oregon and Washington. Louis F. Henderson collected the type specimen near Naches, Washington, in June 1892. 

Eriocoma hendersonii_seed_edited.jpg

Wallowa ricegrass (Eriocoma walllowaensis)

Wallowa ricegrass is an Oregon endemic, growing only in the Wallowa and Ochoco Mountains. Jack Maze and Kali Robson described it as a new species in 1996. It was previously assumed to be Henderson's ricegrass.

This ricegrass also grows on shallow rocky soils. Its panicle is drooping with drooping branches. Like Henderson's ricegrass, the florets are shiny dark brown with a deciduous awn. 

Eriocoma wallowaensis habit.jpg

Little ricegrass (Piptatheropsis exigua)

Piptatherum_exiguum_habit7.jpg

Little ricegrass grows in wonderful subalpine and alpine locations. It forms tight clumps and often has numerous narrow panicles with ascending branches. 

Its florets have relatively short persistent awns. Although they are relatively hairless, they are not dark brown and shiny like the two previous ricegrasses.

Piptatherum_exiguum_habit3.jpg

Rough-leaved ricegrass (Oryzopsis asperifolia)

Oryzopsis_asperifolia_Frater_LR16.jpg

One of the other common names of this species is winter grass. This range of this species doesn't extend into Oregon, not even in alpine habitats. It thrives at high latitudes but not high elevations. Winter grass refers to its leaves that remain green all winter under the snow. The other curious feature of the leaves is that they twist at the base of the blade and lie on the ground with the dorsal side facing up.

In northeastern Washington, this species is often found in the understory of lodgepole pine and western larch forests. Because shaded plants flower only rarely, it took me several years to learn the identity of this grass species. When I finally saw the flowers and "seeds" I was entralled by their beauty. Immediately above the blunt callus is a ring of dense white hairs, like a fur collar. The deciduous awn is relatively short and thin. 

Oryzopsis_asperifolia_floret_LR_LR18_edited.jpg