Agrostis exarata - spike bentgrass
Agrostis exarata is a perennial bunch grass widespread throughout the western USA that grows in moist areas such as riparian zones, shrublands, grasslands, and forest openings at sea level to 2700 m elevation (FNA 1993+; OregonFlora 2022). Spike bentgrass is a disturbance (pioneer) species that prefers open and sunny areas to establish (Esser 1994 and citations therein). It has high ecological value for its ability to colonize disturbed areas and limit the spread of invasive species and is valuable species for use in restoration plantings. It is a valuable horticultural plant for many reasons including its value to livestock, use as a soil stabilizer in disturbed areas, ornamental appeal, and quick growth in cultivation. It is particularly valuable as a forage crop for domesticated (cattle, sheep, and horse) and wild animals (elk and deer) because of its abundance and widespread distribution and herbage that stays green long into the growing season (Esser 1994 and citations therein).
Seed Propagation
Collect fruit when the stem supporting the tissue is dry and brown and/or the fruits are easily dislodged from the plant. The fruits of this species are dispersed by wind so collection at time of seed maturity increases the number of fruits available. The fruits are single seeded grains. Seeds can last more than 20 years in cold, dry storage (5 °C, 25% relative humidity).
Seeds collected in 2001, stored in cold, dry storage, and sown in summer of 2022 had high germination (>75%) within 5 days when sowing. Seeds were sown within Petri dishes containing moist germination paper and placed within a growth chamber at 25/15 °C high/low temperature cycle and 12 hours of white-fluorescent light that coincided to daily high temperature. Seedlings transferred to 48-cell seedling trays in early June formed plugs with firm rootballs less than one month after sowing, and plugs placed in 4-inch pots fertilized with a 1/8 tsp of slow-release fertilizer (15-9-12 NPK) formed landscape ready plants within a month for a total of a 2-month production cycle. Plants were grown within a potting mix (45% mulch, 25% peat moss, 20% pumice, 5% vermiculite and 5% perlite) and placed in a climate-controlled research greenhouse while in seedling trays and outdoors when placed in 4-inch containers in a full sun nursery production system located on the Portland State University campus in Portland, Oregon.
Quick and high germination percentages of 20-year-old seed indicates seeds remain viable for long periods of time in storage. Other Agrostis species also have seeds that remain viable for long periods of time (~10- to 20 years) indicating the potential for long-term seed storage for Agrostis species (Baskin and Baskin 2014 and citations therein). It is unclear if seeds of Agrostis exarata are nondormant or if seeds possess dormancy at maturity and undergo after-ripening in storage. Other species of Agrostis have seeds with physiological dormancy that require pretreatments such as cold stratification before germination occurs (Baskin and Baskin 2014 and citations therein).
References
Baskin, C. and J. M. Baskin. 2014. Seeds: ecology, biogeography, and evolution of dormancy and germination. 2nd ed. Elsevier Inc., San Diego, CA.
Esser 1994. Agrostis exarata. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://www.fs.fed.us/database/feis/plants/graminoid/agrexa/all.html [2022, July 16].
[FNA] Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico [Online]. 22+ vols. New York and Oxford. Website http:// floranorthamerica.org. [accessed March 2022].
OregonFlora. 2022. OregonFlora database and website. Oregon State University, Corvallis, OR. Website: http://oregonflora.org [accessed July 2022].