Animals & Wildlife Magazine

Weed No. 2. Annual Bluegrass (Poa Annua)

By Garry Rogers @Garry_Rogers

Annual bluegrass (Poa annua)

My first year in Humboldt, exceptional summer monsoon and winter rains kept the ground soft for months. In just the short walk to the car, shoes would accumulate layers of mud that left the car carpet stained and forced the shoes to stay outside the door at work. Unfamiliar weeds, some with irritating or painful seeds, filled the fields and bare areas around the house and barn. One of these weeds, Annual bluegrass, covered patches along the driveway. Soft and green that winter and spring, the grass dried during the summer. It provided a yearlong mud-free walkway.

Weed Annual Bluegrass (Poa Annua)

Annual Bluegrass (Poa annua). A. Spikelet. B. Grain. This grass is never more than a foot tall. Its soft green leaves have the closed boat-shaped tips of other Poas (bluegrasses). Leaf sheaths enclose the stems for about 1/3 their length, and ligules are about a tenth of an inch long. The inflorescence is a panicle 1-3 inches long with 2-6 florets on short spikelets. Drawing: Lucretia Breazeale Hamilton. Reproduced with permission of the University of Arizona Press (Parker 1972).

What a great plant. I identified it using Kittie F. Parker’s Illustrated Guide to Arizona Weeds (Parker 1972) and headed for town. I asked about seeds at the local building-supply where lawn-grass seeds sold. After a reflective moment, the store employee fulfilled his customer-service obligation without detectable sarcasm and stated that no one wanted Annual Bluegrass seed. “It’s a weed.” No seed was available.

Despite its small size and mild demeanor, Annual Bluegrass has traveled with people from its Eurasian home to establish in every continent. In America, Sereno Watson found it in the Great Basin Desert of Utah and Nevada during the 1872 exploration of the fortieth parallel. He “collected [it] on stream-banks in cañons (sic) near roads traveled only by teams of woodmen” –Watson (King 1872: xli).

I never found any Annual Bluegrass seed. After twenty years here, I’ve covered the mud with gravel, concrete sidewalks, and perennial plants, but patches of the little grass are still present beside the driveway and always trying to creep into the lawn. Its area has shrunk as my well-watered perennial lawn grasses have crowded its space. I could easily till and reseed it away now, but I guess I’ll let it be.

References:

Introduction to Weeds.

King, C. 1871. Geological exploration of the fortieth parallel. Professional Papers of the
Engineer Department, U. S. Army, No. 18. Government Printing Office,
Washington. 525 p.

Parker, K. F. 1972. An illustrated guide to Arizona weeds. University of Arizona Press,
Tucson, AZ. 338 p.


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