The “Bad” Grass List

By Kevin Noon and Cathy Lewis

Grass AwnWe currently know of or suspect several grass species as dangers to our dogs. These species have two characteristics of the floret that make them particularly insidious. The basal extension of the lemma (sheath or bract) around the grass floret comes to a very sharp point as the floret matures and dries out at the end of clip_image002the plants’ growing season. And the lemma is covered with tiny hairs pointing away from the sharp basal point. As the florets mature, they fall off easily. They can be inhaled into the throat or lungs of a dog, swallowed, caught between the toes, become lodged in the fur, or fall into the ear canal. Once attached, the direction of the basal hairs creates a “barbed” effect which keeps the floret from backing out of the fur or tissue. As the animal moves the floret constantly migrates forward pushing the pointed base further into the tissue.

Once inside the tissue these florets have been known to migrate anywhere inside the body including through organs, down the spinal column, through the eyes, and up the limbs. Aside from the damage and infection caused by the migration, some florets carry bacteria that can cause serious infections depending on where they are located.

The following is a list of the most common grasses with these characteristics that dog owners and veterinarians across the country have identified. The worst known hazards are shown in red. The links provided contain additional information and/or photographs.

Cheatgrass/Downy brome Bromus tectorum Photos in site Gallery
Ripgut Brome Bromus rigidus

Canada Wild Rye Elymus canadensis Photos in site Gallery
Virginia Wild Rye Elymus virginicus
Great photos:

Foxtail Barley Hordeum jubatum Photos in site Gallery
Awn photo:
Needle and Thread Stipa comate
Western Needlegrass Stipa occidentalis
California Needlegrass Stipa pulchra CA only
Sleepygrass/Tall Needle grass Stipa robusta
Winter Redtop/winter bentgrass/ticklegrass Agrostis hiemalis or Agrostis hyemalis
Red Three-Awn Aristida longiseta
Single-Awn Aristida Aristida orcuttianas CA, AZ, NM, TX
Oldfield Threeawn Aristida oligantha
Nimblewill Muhlenbergia schreberi
This plant was suggested as problematic by a plant biologist at U of Minnesota. On inspection, it doesn’t appear immediately to have an aggressive awn, but better to provide the information as potential hazard than not.

NRCS database (main):
Line drawings of various grasses/identification guide:
More photographs of many grasses:

© Cathy Lewis & Kevin Noon, 2010

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