{"id":3701,"date":"2026-09-09T22:55:52","date_gmt":"2026-09-09T22:55:52","guid":{"rendered":"https:\/\/keyapa.com\/sp\/?p=3701"},"modified":"2026-09-09T23:08:27","modified_gmt":"2026-09-09T23:08:27","slug":"defining-grasses-the-amazing-awns-of-grasses","status":"publish","type":"post","link":"https:\/\/keyapa.com\/sp\/2026\/09\/09\/defining-grasses-the-amazing-awns-of-grasses\/","title":{"rendered":"Defining Grasses: The Amazing Awns of Grasses"},"content":{"rendered":"\n
\"Arrhenatherum
Arrhenatherum elatius<\/em> in Copenhagen.<\/figcaption><\/figure>\n\n\n\n

If one were in the habit of identifying grasses, then the presence of visible and distinctive structures on the spikelets would be one way to ease the pain of such an endeavor. Fortunately, many grasses have long projections from these reproductive structures that go a long way towards helping the observer. These so-called awns<\/strong> are long bristle-like projections on the floral bracts of grass spikelets that are structurally diverse and widespread. Although they are found in a few other plants, the Poaceae have the most diverse and abundant panoply of awns.<\/p>\n\n\n\n

\"Spikelets
Spikelets with awns (from Petersen and Kellogg. 2022).<\/figcaption><\/figure>\n\n\n\n

Most awns arise from the lemmas of a spikelet, usually from the mid-vein, but some originate from the glumes, and more rarely from the palea. Many are straight, others are geniculate (bent), and two other types are specific towards some taxa. The Aristida for example, have coiled awns, while the Streptochaeta have branched awns. <\/p>\n\n\n\n

\"Avena
Avena fatua<\/em> with geniculate (bent) awns rising from the lemma.<\/figcaption><\/figure>\n\n\n\n

The function of awns has been studied but still presents some mysteries. The most obvious is that they are involved in reproduction. In the case of grasses, the awns might aid in dispersal of the diaspore (the dispersal unit of grasses). These can be grouped into three types.<\/p>\n\n\n\n

(1) The awns aid in making sure seeds drop straight down to the ground, similar to how a parachute can stabilize a dropping package. This is important to grasses because having the base of the seeds (the callus) grounded increases germination. <\/p>\n\n\n\n

\"Piptochaetium
Piptochaetium<\/em> sp (Speargrass) with long straight awns at Wekiwa Springs State Park.<\/figcaption><\/figure>\n\n\n\n

(2) The awns may also allow attachment of the diaspore to passing animals, who then carry it far from the original location. One is easily reminded of this when wading through a field of grass and emerging with many grass seeds embedded in clothing, or bemoaning the sight of a pet dog dappled with sticky particles on their fur.<\/p>\n\n\n\n

\"Nassella
Nassella tenuissima<\/em> spikelets with long straight awns in Cerritos, California.<\/figcaption><\/figure>\n\n\n\n

(3) The most dramatic way they aid in dispersal are in those seeds that have hygroscopic awns that twist and untwist in response to changes in moisture. The movement of the awns allow the seeds to either walk across the ground (see video below).<\/p>\n\n\n\n

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