Perenniality in Poa annua L.

Experiments were conducted to determine identification methods that could be used to differentiate annual and perennial plant types within the species Poa annua L. Thereafter, Poa annua plants were collected from numerous turfed areas in three Northern Pacific Coastal regions and identified as annual or perennial biotypes. It was found that annual growth forms were characterized by lower leaf and node numbers, lower secondary tiller numbers, and lower adventitious root numbers. The annuals also reached reproductive maturity quicker than the perennials and had a greater percentage of flowering tillers at the completion of the test. Morphological characteristics that were not useful included blade length and width, ligule length, culm length, inflorescence characteristics, primary tiller number, shoot and root dry weight, and seminal root number. An examination of seed characteristics showed a post harvest dormancy requirement in annual Poa annua. Seed from perennial types germinated immediately following harvest. Poa annua plants collected from numerous turfed locations were identified as annual or perennial biotype based on the above differences, It was found that in excess of 50 percent of the samples exhibited perennial characteristics and that both types were quite evenly distributed throughout Oregon and Western Washington. Results showed that the perennials were most often collected from areas that received moderate or intensive supplemental irrigation. The annuals predominated in non-irrigated golf course roughs. Descriptive botanical literature on variation in Poa annua indicated that the subspecies taxonomic designation would be appropriate to distinguish between the annual and perennial types. It was suggested that all annuals be classified in the subspecies annua and the perennials in subspecies reptans

Fall 1976

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