Douglas’ Bluegrass (Poa douglasii)


If you’ve been a long-time reader of this column, you probably know that I have a thing for our native grasses. Previous discussions have covered Pacific reedgrass (Calamagrostis nutkaensis, June 2006), purple needlegrass (Nassella pulchra, September 2006), and coastal terrace prairie (December 2006). Depending on your appreciation for grasses, you may have found these articles either wonderfully informative or painfully tedious.

The first challenge most people face with grass identification is one of basic vocabulary; grass flower parts just don’t jibe with our usual notions of what makes up a flower. No petals or sepals; instead, there are glumes, lemmas and paleas. Spikelets, florets, awns, sheaths, ligules, and other body parts add to the confusion. Another hindrance to a better understanding of this group, at least for those of us with aging eyesight, is the fact that most grass flowers are TINY! They are best viewed hunched over a dissecting scope (I’m sure you all have one of those handy) with a dissecting needle in each hand and tweezers in your toes. And for folks like me who suffer from hay fever (I am especially allergic to grass pollen—bad career counseling), a walk in the meadow can bring on physical discomfort. But I assure you, armed with a simple hand lens, a botanical glossary, and a handful of Benadryl, you too can overcome these hurdles. After all, grasses probably contribute more to the greening of your immediate surroundings than any other plant group. In fact, it is estimated that grasses constitute fully 20 percent of the world’s vegetative cover. So why not get to know them?

The best glossary I know (it resides permanently next to my scope and Jepson Manual ) is Plant Identification Terminology: an Illustrated Guide, by Harris and Harris, 2001 ( $18.95). This small, novice-friendly paperback, with definitions and illustrations of every botanical term you’re likely to ever come across, is absolutely invaluable. A nice introductory book is Grasses in California, by Crampton, 1974 ( $14.95). For the real grass enthusiast, there is the most useful two-volume 1971 Dover reprint of the 1950 Hitchcock classic Manual of the Grasses of the United States ( $16.95 per volume). And, while I have not yet seen the new California Grasslands, edited by Stromberg, Corbin, and D’Antonio, 2007 ( $55), it’s sure to become a valuable addition to my library. (You can browse all these books at the San Francisco Botanical Garden Library.)

Due to popular demand (ok, our chapter president made a passing suggestion), I bring you another of our lovely perennial grass species, Douglas’ bluegrass. I won’t repeat earlier discussions of the wonderfully diverse and fascinating grass family (Poaceae or Gramineae) or of native bunchgrass grasslands (see the above-mentioned articles on our chapter website ). But this article wouldn’t be complete without a few basic facts. Worldwide, there are more than 9,000 species of grasses in 650 genera, comprising about 3.6 percent of all flowering plant species. California is host to about 580 taxa of grasses (364 native and 217 naturalized nonnative) belonging to 121 genera. Grasses are indeed flowering plants, belonging to the same Division (Anthophyta) as magnolias, roses, petunias, and pansies. By way of refresher, flowering plants are divided into two Classes: the so-called dicots (Class Magnoliopsida) and the monocots (Class Liliopsida). In addition to the grasses, monocots include the lilies, palms, bamboos, orchids, bromeliads, agaves, onions, rushes, sedges, cattails, iris, and philodendrons, to name just a few.

The genus Poa, the namesake of the family, is one of the most diverse in terms of number of species. The Flora of North America lists 91 Poa species. California boasts 36 native taxa, and hosts another ten nonnative species that have become naturalized. Members of the genus, usually lumped together under the moniker “bluegrass,” include both annuals and perennials. The majority of our native bluegrass species are perennials (22 perennials versus 3 annuals). The species with the widest distribution is one-sided bluegrass (P. secunda), which occurs across the length and breadth of the state, from sea level to above 12,000 feet. Howell’s bluegrass (P. howellii ) and Bolander’s bluegrass (P. bolanderi ) are also recorded from the Mexican border to Oregon, although the former is restricted to elevations below 3,200 feet while the latter occurs between 5,000 to 10,000 feet. Most of the remaining native species exhibit a geographic distribution restricted by habitat type, latitude, and/or elevation. Seven of our bluegrass species have special status; two are federally listed endangered species, three are CNPS List 2 species, and two are CNPS List 4 species.

Douglas’ bluegrass is a tufted perennial developing from long rhizomes or stolons. One of only three overlapping species that occurs on dunes (the others being P. confinis and P. macrantha), it is distinguished by its relatively longer (>>0.18 inch) lemmas and scabrous to coarsely hairy stems. Douglas’ bluegrass is also dioecious, which means it produces male and female flowers on separate plants. The dense inflorescences develop at the top of short (one- to three-inch) stems, appearing from April through June. It is a relatively common constituent of shifting coastal dunes and sandy soil on coastal bluffs below 300 feet in elevation, occurring from Santa Barbara County in the south to Del Norte County in the north.

Douglas’ bluegrass is not a rare species. It has no status under the federal or State endangered species acts, and it is not listed as rare, threatened, or endangered by CNPS nor considered locally significant by our local chapter. But, by virtue of its habitat affinities, you can be sure that it is not common in our chapter area; there aren’t many examples of these habitats left in San Francisco.

In San Francisco, Douglas’ bluegrass is known historically from Lone Mountain and the bluffs of the seashore (Brandegee 1891); and near Point Lobos, in the Richmond District, and on the dunes of the Sunset District (Howell, et al. 1958). It can still be found today along the western ridge line of the Sunset District at Hawk Hill, Grandview Park, and the Sunset rock outcrops. It can also be found at the Presidio (south end of Baker Beach and Crissy Field), Lake Merced, and Fort Funston.

The next time you drive down The Great Highway, make a note of the dense grasses that were planted there to stabilize the drifting sands when the road was rebuilt about a dozen years ago. What you’re seeing is the invasive nonnative European beachgrass (Ammophila arenaria). Now try to imagine that same area revegetated with all the indigenous elements that once occurred here like Douglas’ bluegrass, American dunegrass (Leymus mollis ssp. mollis), beach bursage (Ambrosia chamissonis), beach morning glory (Calystegia soldanella), yellow sand verbena (Abronia latifolia), beach pea (Lathyrus littoralis), dune sagebrush (Artemisia pycnocephala), dune buckwheat (Eriogonum latifolium), beach evening primrose (Camissonia cheiranthifolia), among many, many others. In the words of the Beach Boys, “Wouldn’t it be nice?” In fact, such restoration efforts are ongoing. The best examples are underway at Baker Beach and Crissy Field. If you’d really like to get some hands-on experience and get to know these species up close and personal, try joining one of the volunteer work parties hosted by the Presidio Park Stewards