Abstract:
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.
