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Lyme grass plants

Lyme grass or sand ryegrass (Leymus arenarius or Elymus arenarius)

An invasive grass in coastal regions. Its form of fast vegetative growth can negatively affect native beach and dune vegetation. As Lake Michigan's water levels have gone down, more areas have been colonized by this species. Stems are smooth, round and stout; the plant is 2-4’ tall.


Regulated areas of lyme grass
Lyme grass is Prohibited (Red counties) and Restricted (Orange counties)

Other names for this plant include:

  • Common names: Sand ryegrass
  • Scientific names: Elymus arenarius

Ecological threat:

  • Can grow in variety of habits, but is especially concerning on the shores of the Great Lakes. With a spreading root system, lyme grass can stabilize our naturally shifting dunes and compete with rare grasses.
  • Occupies the same dune habitat and poses a threat to several native rare plants which include: Elytrigia dasystachya, Calamovilfa longifolia, Salix cordata, Cirsium pitcheri, Solidago simplex, Cakile lacustris, and Euphorbia polygonifolia.

Classification in Wisconsin: Prohibited/Restricted (Restricted in Door, Kenosha, Kewaunee, Manitowoc, Milwaukee, Ozaukee, Racine, and Sheboygan counties; Prohibited elsewhere)

Species Assessment Groups (SAG) were assembled to recommend a legal classification for each species considered for NR 40. The recommendation for lyme grass was based upon this literature review developed by the department.


Leaves: Broad, rigid, straight, with a short ligule; blueish in color. 12” long and 0.5” wide.

Flowers: Dense spikes with 3 flowered spikelets; glumes are not longer than the spikelets. Flowers in July. Spikes are blue-green in early summer and turn beige later in the season.

Roots: Rhizomes.

Similar species: American dune grass (Ammophila breviligulata Fernald) has green leaves and is less robust. Thick-spike wheat grass (Elymus lanceolatus) is very similar in size and color but has a spike thickness of 5-10 mm compared to lyme grass which has a spike thickness of 15-25 mm. There are more characteristics within the inflorescence that can help discern the two species and others, however, please refer to a regional biologist for identification.


Known county distribution of lyme grass
Counties in WI where lyme grass has been reported (as of July 2011). Both vouchered and unvouchered reports included.

Do you have lyme grass in your county but it isn't shaded on the map? Send us a report.


Mechanical: Not recommended control.

Chemical: Foliar treat stems with Habitat (Imazapyr) herbicide mixed with Tactic surfactant at a rate of 1.5 ounces of each product per gallon of water. Applications may be made as early as June through early October as long as the leaves are still green. Several applications may be needed.


View lyme grass pictures in our photo gallery!


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Last revised: Monday June 03 2019