{"id":2173,"date":"2026-03-25T13:51:45","date_gmt":"2026-03-25T20:51:45","guid":{"rendered":"http:\/\/smallgrains.wsu.edu\/weeders-of-the-west\/?p=2173"},"modified":"2026-03-26T08:53:37","modified_gmt":"2026-03-26T15:53:37","slug":"grassweed","status":"publish","type":"post","link":"https:\/\/smallgrains.wsu.edu\/weeders-of-the-west\/2026\/03\/25\/grassweed\/","title":{"rendered":"Grass Weed Emergence in Fall 2025"},"content":{"rendered":"

Contributed by Judit Barroso, Oregon State University<\/p><\/div>\n<\/div>\n<\/div><\/div>\n

This year\u2019s weather has been anything but typical. At the CBARC station (Adams, Oregon), September and October brought 153% and 122% more precipitation than normal, but the trend reversed in November, December, and January that were 96%, 99%, and 23% drier than average. With these kinds of unusual shifts, we launched a study this fall to better understand how grass weeds germinate under varying conditions. Our long-term goal is to develop predictive germination models using multi-year data. These models could help growers anticipate weed emergence based on seasonal weather patterns, ultimately improving herbicide timing and reducing the soil seedbank.<\/p>\n

For this first year, we worked in a fallow field at CBARC. We set up four plots and placed three permanent sampling frames (13 \u00d7 12 inches) in each one (Image\u202f1). In total, we monitored 12 frames every other week from September 23 through December 23, which is when colder temperatures led to a clear decline in germination and resumed sampling on February 16, 2026. During each sampling event, we removed, identified, and counted all grass seedlings. The species we documented included downy brome (Bromus tectorum)<\/em>, jointed goatgrass (Aegilops cylindrica)<\/em>, feral rye (Secale cereale)<\/em>, and volunteer wheat (Triticum aestivum)<\/em> (Image\u202f2).<\/p><\/div>\n<\/div>\n<\/div><\/div>\n

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<\/figcaption>\n<\/figure>\n<\/div>\n
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<\/figcaption>\n<\/figure>\n<\/div>\n<\/div><\/div>\n
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Image 2. Detail of the germination of jointed goatgrass (left seed), wheat (central seed), and downy brome (several seeds on the right).<\/figcaption>\n<\/figure>\n

The numbers we\u2019ve collected so far are striking. Altogether, we counted 9,767 grass seedlings\u2014an average of 2,442 per plot and 814 per square foot. Of these, 71% were downy brome, 22% volunteer wheat, 3.5% jointed goatgrass, and 1.8% feral rye. When we look at relative emergence patterns (Figure\u202f1), downy brome stands out. While jointed goatgrass, feral rye, and volunteer wheat showed peak emergence on our third sampling dates (10\/21\/2025), downy brome peaked much earlier, on our very first sampling date (9\/23\/2025). This early flush is likely tied to its small seed size and its ability to germinate right on the soil surface, especially when residue helps conserve moisture.<\/p>\n

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Figure 1. Relative emergence (%) of downy brome (DB; Bromus tectorum), jointed goatgrass (JGG; Aegilops cylindrica), volunteer wheat (VW; Triticum aestivum) and feral rye (Rye; Secale cereale) in fallow of 2025 at the Columbia Basin Agricultural Research Center, Adams, Oregon.<\/figcaption>\n<\/figure>\n

We also examined how precipitation patterns might relate to emergence (Figure\u202f2). In this first season, we did not find a correlation\u2014soil moisture simply didn\u2019t seem to limit germination last fall. Looking ahead, we hope to expand the study by adding a second site in northeastern Oregon and sites in Idaho and Washington<\/span>. The goal is to build a regional, multi-state collaboration across the Pacific Northwest that will strengthen the accuracy and usefulness of future weed germination models, which we envision to include some broadleaf weeds as well. Your feedback helps guide our work. Please, let us know which weed species you are most interested in learning about and the region you farm, so we can direct our efforts more effectively.<\/p><\/div>\n

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Figure 2a. Rain events in the fall and winter of 2025 (Precip; blue bars) and relative grass emergence sampled in the fall and on February 26, 2026 (color dots).<\/figcaption>\n<\/figure>\n
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Figure 2b. Precipitation accumulated 15 days before each weed sampling (blue bars) and relative grass emergence in fallow in the fall of 2025 (dots and color lines).<\/figcaption>\n<\/figure>\n<\/div>\n<\/div><\/div>\n<\/p>\n","protected":false},"excerpt":{"rendered":"

With the unusual weather shifts this past year, Oregon State University researchers studied how grass weeds germinate under varying conditions. Their long-term goal is to develop predictive germination models using multi-year data.<\/p>\n","protected":false},"author":4524,"featured_media":737,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[8],"tags":[],"_links":{"self":[{"href":"https:\/\/smallgrains.wsu.edu\/weeders-of-the-west\/wp-json\/wp\/v2\/posts\/2173"}],"collection":[{"href":"https:\/\/smallgrains.wsu.edu\/weeders-of-the-west\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/smallgrains.wsu.edu\/weeders-of-the-west\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/smallgrains.wsu.edu\/weeders-of-the-west\/wp-json\/wp\/v2\/users\/4524"}],"replies":[{"embeddable":true,"href":"https:\/\/smallgrains.wsu.edu\/weeders-of-the-west\/wp-json\/wp\/v2\/comments?post=2173"}],"version-history":[{"count":20,"href":"https:\/\/smallgrains.wsu.edu\/weeders-of-the-west\/wp-json\/wp\/v2\/posts\/2173\/revisions"}],"predecessor-version":[{"id":2198,"href":"https:\/\/smallgrains.wsu.edu\/weeders-of-the-west\/wp-json\/wp\/v2\/posts\/2173\/revisions\/2198"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/smallgrains.wsu.edu\/weeders-of-the-west\/wp-json\/wp\/v2\/media\/737"}],"wp:attachment":[{"href":"https:\/\/smallgrains.wsu.edu\/weeders-of-the-west\/wp-json\/wp\/v2\/media?parent=2173"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/smallgrains.wsu.edu\/weeders-of-the-west\/wp-json\/wp\/v2\/categories?post=2173"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/smallgrains.wsu.edu\/weeders-of-the-west\/wp-json\/wp\/v2\/tags?post=2173"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}