Pseudoroegneria spicata- bluebunch wheatgrass or Ag spic in the Wenatchee Foothills during early winter.

A common perennial grass found at lower to middle elevations, occurring in shrub steppe to Ponderosa pine forests, from Alaska to Mexico and as far east as New Mexico and Saskatchewan. This is a native bunchgrass- and unlike the grass we typically think of in our lawns (Kentucky bluegrass), it  grows from a single clump. Over time the clump becomes larger and can reproduce through tillers (leafy shoots with roots) but it doesn’t have rhizomes like lawn grass (Poa pratensis). Previously it was scientifically classified in the Agropyron genus and known to old range-cons and cowboys as “Ag Spic”.

An ecological function that bluebunch wheatgrass does is to prevent erosion and mud slides. The roots of the grass typically grow up to 5 ft. deep and 2ft. wide, helping to stabilize the soil and prevent loss by wind and water.

Because bluebunch wheatgrass grows in clumps, when fires occur there is not continuous fuel for the fire to spread. It helps to decrease fire frequency and intensity. Invasive non-native annual grasses such as cheatgrass provide a highly flamable and continuous fuel source for fire to spread.

Bluebunch wheatgrass is a C₄ plant. There are three types of photosynthesis- C_3, C₄, and CAM photosynthesis. Most plants are C_3. C₄ plants have a special adaptation which allows them to photosynthesize and grow during extreme environmental conditions such as drought, high temperatures and nitrogen or CO₂ limitation. 97% of the water taken up by C₃ plants is lost through transpiration, compared to a much lower proportion in C₄ plants, extremely helpful in a dry environment. CO₂ is taken up by the plant quicker in C₄ plants, allowing for the plant to close its stomata and conserve water. C₄ plants can also photosynthesize quicker in high temperatures and light than C₃ plants.

Other adaptations that help bluebunch wheatgrass do well in hot arid environments is that it is a cool season grass- meaning it grows vigorously when it is cool in spring and fall and is dormant for much of the hottest part of the summer. There is also a special type of fungi which attaches to its roots and helps the grass roots to absorb nutrients- principally phosphate- from the soil and increases the plants’ drought tolerance. This type of fungi is called VAM or vesicular arbuscular mycorrhizas which never produce a mushroom, but live out their lifespan entirely beneath the soil. Most plants in the shrub-steppe are associated with VAM fungi and some are dependent on it and won’t germinate and/or grow without the fungi in the soil.

Pseudoroegneria spicata ssp. inermis. Photo courtesy of USDA-NRCS PLANTS Database / Hitchcock, A.S. (rev. A. Chase). 1950. Manual of the grasses of the United States. USDA Miscellaneous Publication No. 200. Washington, DC.

Pseudoroegneria spicata ssp. spicata. Photo courtesy of USDA-NRCS PLANTS Database / Hitchcock, A.S. (rev. A. Chase). 1950. Manual of the grasses of the United States. USDA Miscellaneous Publication No. 200. Washington, DC.

There are two subspecies of Pseudoroegneria spicata- ssp. spicata and P. s. ssp. inerme. The only difference between the typical subspecies of bluebunch wheatgrass and beardless bluebunch wheatgrass is the presence or absence of divergent awns. The two subspecies are occur together and hybridize making identification to subspecies difficult.

Also, it used to be thought there was another variety or subspecies- var. pubescens which is now just considered a hairier variant within ssp. spicata. Bluebunch wheatgrass also hybridizes with Elymus species, compounding identification problems at times.

Bluebunch wheatgrass is known as one of the better grasses for forage. In spring it has the highest nutrition because of new growth and is 20% protein and 45% carbohydrate. It cures well and makes for good standing winter feed for deer and elk, but also for grazing cattle- the absence of it is often an indicator of overgrazing. Heavy grazing causes lower energy to be stored by the plant in the stems and roots, and the grass can die in the winter without adequate energy reserves.

In southern Idaho the early pioneers and settlers were dependent on cattle ranching for subsistence, and it is still the main form of income for many living in rural areas. While I was in southwest Idaho recently, good patches of this bluebunch wheatgrass were exceedingly few and far between. There is a small protected area of BLM Land that was classified as an ACEC (Area of Critical Environmental Concern) near Murphy Idaho because it contained one of the few remaining healthy stands of bluebunch wheatgrass.

Cherry tree in Wenatchee.

The Wenatchee area situation is different because the settlers and early farmers were orchardists instead of ranchers. This preserved the native landscape surrounding the towns and orchards, and for the most part- bluebunch wheatgrass is common in the foothills and mountains. Lack of grazing animals also meant that the herbaceous plants were preserved in this area, and today we enjoy riotous wildflowers covering the hillsides all thanks to a vibrant regional economy in fruit.

To the north and south of Wenatchee the situation is somewhat different and more ranching based, but there are also millions of acres of public lands that have escaped heavy grazing. To the east of Wenatchee is the Columbia Plateau which is also somewhat degraded from cattle grazing, but is mainly wheat fields, although there are gems of the shrub-steppe that have been spared there too.

A closely related species from Russia, Agropyron cristatum- crested wheatgrass, was widely used in rangeland plantings and to revegetate road cuts throughout the west. In much of the prior range of bluebunch wheatgrass, crested wheatgrass and desert wheatgrass are now the dominant grasses.

Links

• USDA Plants Profile for Pseudoroegneria spicata- bluebunch wheatgrass
• Photosynthesis- Wikipedia
• VAM- Vesicular Arbuscular Mycorrhizas